BRUNO BRISEGHELLA - personale UniMoRe

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BRUNO BRISEGHELLA

Professore Ordinario
Dipartimento di Ingegneria "Enzo Ferrari"

Pubblicazioni

2023 - Effect of Pre-Hole Filled with High-Damping Material on the Inelastic Response Spectrum of Integral Abutment Bridges [Articolo su rivista]
Aloisio, A; Pelliciari, M; Xue, Jq; Fragiacomo, M; Briseghella, B
abstract

This paper estimates the effect of a pre-hole filled with high-damping material on the inelastic response spectrum of Integral Abutment Bridges (IAB) with pile foundation. The hysteretic response of the pile, described by a Winkler beam model, is obtained from the piece-wise definition of the subgrade stiffness, calibrated on experimental data. The pre-hole with damping pre-hole determines a reduction of the demand spectral acceleration. The force modification factors of the acceleration response spectrum of the bridge superstructure under a large set of strong/motion earthquakes are estimated. The force-reduction factors for the elastic design of IABs with damping pre-hole are proposed.

2023 - Effect of pinching on structural resilience: performance of reinforced concrete and timber structures under repeated cycles [Articolo su rivista]
Aloisio, A.; Pelliciari, M.; Bergami, A. V.; Alaggio, R.; Briseghella, B.; Fragiacomo, M.
abstract

This article attempts to define pinching of two structural joints, reinforced concrete (RC) and wood ones. In particular, the research outlines differences and analogies between pinching of an RC portal and a Light Timber Frame (LTF) wall. This is done by focusing on the concavity of pinching in their response under repeated cycles, which produces differences in the energy dissipation. The response of the two structural archetypes under pseudo-static and dynamic simulations is analysed using the Atan hysteresis model modification. The truncated incremental dynamic analysis (TIDA) of the two systems modelled as single-degree-of-freedom (SDOF) oscillators yielded the fragility curves, approximated by a lognormal cumulative distribution (CDF). The stability of RC under repeated cycles reveals its significant resilience compared to LTF structures. The examination of the fragility functions supports a discussion about the relation between the pinching concavity and the notion of structural resilience by introducing a robustness index ranging from 0 to 1. Ultimately, a parametric analysis of a fictitious structural system derived from the timber one by varying the concavity of the pinching path leads to the estimation of the robustness index as a function of the pinching concavity.

2023 - NOx degradation ability of S-g-C3N4/MgAl-CLDH nanocomposite and its potential application in cement-based materials [Articolo su rivista]
Yang, Z.; Xiong, X.; Yan, X.; Luo, S.; Zhang, Y.; Briseghella, B.; Marano, G. C.
abstract

In this study a new photocatalytic nanocomposite, S-g-C3N4/MgAl-CLDH, was synthesized and implemented into cement mortar by internal mixing or coating. The photocatalytic NOx degradation efficiency of the S-g-C3N4/MgAl-CLDH and photocatalytic mortar was investigated. The NOx degradation efficiency and photoluminescence spectra of S-g-C3N4/MgAl-CLDH after being immersed in the simulated concrete pore solution were evaluated to assess its chemical stability. The results show that compared with S-g-C3N4, the S-g-C3N4/MgAl-CLDH exhibits a narrower bandgap (2.45 eV), a lower photogenerated electron-hole pair recombination rate and a higher specific surface area (36.86 m2 g−1). After 21 min of visible light irradiation, the NOx degradation rate of S-g-C3N4/MgAl-CLDH achieves 100% as compared to merely 81.5% of S-g-C3N4. After being submerged in simulated concrete pore solution, the S-g-C3N4/MgAl-CLDH exhibits only a slight decrease of 5% in degradation rate after 12 min of irradiation, confirming a good compatibility and stability in cement-based materials. The NOx degradation ability of the internally mixed mortar is enhanced with an increase in the dosage of S-g-C3N4/MgAl-CLDH. For coated mortar, in contrast, a decline in NOx degradation rate is observed after 5 layers of coating owing to the lower porosity of mortar after excessive coating.

2023 - Probabilistic formulation for the q-factor of piles with damping pre-hole [Articolo su rivista]
Briseghella, Bruno
abstract

The flexibility of the foundation system significantly affects the seismic and operational performance of integral abutment bridges (IAB). The so-called pile isolation system can lead to higher flexibility in pile foundations. It consists in backfilling the pile hole with high-damping materials up to a certain depth from the surface level. However, the impact of this solution in increasing the lateral flexibility and reducing the seismic demand strongly depends on the scale factor and pile diameter. Most investigations on this topic are based on experimental tests on scaled pile specimens. This paper explores the pile isolation system’s effectiveness by conducting a multivariate sensitivity analysis of the seismic demand of an IAB structural archetype. The IAB archetype is modelled as a Winkler beam with a piece-wise definition of the subgrade stiffness and equivalent viscous damping, simulating the responses of the soil and high-damping particles. The simulated data are then used to calibrate a probabilistic formulation of the seismic demand reduction due to the pre-hole. The formulation, calibrated following a Bayesian approach, is used to derive estimates of the q-factor associated with the damping pre-hole for possible use in engineering practice. The analyses demonstrate that pile isolation with high-damping material can be effective but possesses a limited dissipating capacity, with a seismic reduction factor of approximately 1 and 2.

2023 - Repair of reinforced concrete bridge columns subjected to chloride-induced corrosion with ultra-high performance fiber reinforced concrete [Articolo su rivista]
Briseghella, Bruno
abstract

The rehabilitation of reinforced concrete (RC) bridge columns subjected to chloride-induced corrosion is addressed in the present paper. The proposed strategy is based on the replacement of the original external layer made of normal-strength concrete (NSC) with ultra-high performance fiber reinforced concrete (UHPFRC), and it additionally involves the substitution of the existing corroded longitudinal reinforcement with new machined steel rebars. This repair technique aims at restoring strength, stiffness, and ductility of the original column in a short time without altering its cross-section dimensions. Because of the high compactness of the UHPFRC, it also serves at improving its durability. The main contribution of the present work is a numerical investigation carried out in order to identify how the design decisions about the repair strategy influence the behavior of the restored column. The parametric investigation reveals that the length of the zone in which NSC is replaced by UHPFRC as well as the machined index (i.e., ratio between turned and original rebar cross-section area) must be properly selected to make the intervention effective. Numerical results also highlight that the main design issue to deal with is the relocation of the plastic hinge from the repaired zone towards the weak unrepaired part of the column. Practical design recommendations are finally formulated.

2022 - Cable optimization of a cable-stayed bridge based on genetic algorithms and the influence matrix method [Articolo su rivista]
Feng, Y.; Lan, C.; Briseghella, B.; Fenu, L.; Zordan, T.
abstract

Structural optimization is an important tool for structural designers that helps them to find innovative design solutions and structural forms with a better exploitation of materials as well as decreased self-weight and minimum material costs. In this article, a design procedure coupling the influence matrix method and genetic algorithms to optimize stay cables in cable-stayed bridges is presented. Following that, the design procedure is utilized in the preliminary design of a twin towers double-cable planes cable-stayed bridge to be located in Ferrara, Italy. The cable cross-sectional areas and corresponding pre-tension forces are optimized simultaneously. The results demonstrate that the proposed procedure is a powerful tool for designing stay cables and predicting the optimum cross-sectional areas of stay cables under certain stress and displacement constraints.

2022 - Damage-Based Hysteresis Bouc-Wen Model for Reinforced Concrete Elements [Relazione in Atti di Convegno]
Sirotti, S.; Pelliciari, M.; Briseghella, B.; Tarantino, A. M.
abstract

2022 - Dynamic assessment, FE modelling and parametric updating of a butterfly-arch stress-ribbon pedestrian bridge [Articolo su rivista]
He, L.; Castoro, C.; Aloisio, A.; Zhang, Z.; Marano, G. C.; Gregori, A.; Deng, C.; Briseghella, B.
abstract

The article focuses on the dynamic identification and finite element (FE) modelling of a butterfly-arch stress-ribbon pedestrian bridge in Fuzhou, Fujian, China. The Stochastic Subspace Identification method yields an estimate of the operational modal parameters. A highly synchronous tri-axial wireless sensor network was deployed on the bridge deck to record the structure’s ambient vibration. Eight stable modes in the frequency range 3.59–14.92 Hz were found, associated with prevalent bending and torsional deformations. Four distinct FE models of the bridge with progressive complexity and accuracy were developed to investigate the sensitivity of the modal features to the modelling choices. The FE model characterised by the fittest agreement with the experimental modal parameters was used for the automatic parametric optimisation based on a sensitivity-based algorithm. The stiffness of the springs simulating the soil-structure interaction, the elastic modulus of the concrete deck and the elastic modulus of the tendons were chosen as updating parameters for a total of eight parameters. The effect of non-structural elements (handrails) and prestress on the modal features are also investigated. The final advanced FE model developed can serve as baseline for a long-term monitoring of the bridge during its life-cycle, and also provides some recommendations to practitioners and scholars all over the world for the modelling and analysis of this particular kind of footbridges.

2022 - Editorial [Articolo su rivista]
Briseghella, B.
abstract

2022 - FRP Reinforcement to Retrofit Bridge Pier After Repair: Experimental Test Results [Relazione in Atti di Convegno]
Xue, J.; Lavorato, D.; Fiorentino, G.; Bergami, A. V.; Briseghella, B.; Nuti, C.
abstract

Reinforced concrete (RC) bridge piers damaged after a strong earthquake are repaired. The damaged concrete and the steel reinforcement parts are replaced by rebar segments connected to the existing rebar parts by welding connections and by a self-compacting concrete jacket respectively. A modest transverse steel reinforcement, not sufficient to improve the seismic pier capacity, is used to simplifies the concrete cast in modest volumes. After the repair, a carbon fiber reinforced polymer (Carbon FRP) reinforcement is applied to enhance the pier ductility and the shear strength. Three RC circular columns, representative of piers, were repaired and reinforced by the proposed strategy to be tested in lab applying a deformation history due to a strong earthquake. The piers were able to sustain very strong seismic demand and therefore the proposed repair and retrofitting interventions are effective. The strain distribution of the Carbon FRP reinforcement was measured and discussed to increase the very modest database presented in the literature.

2022 - IMPA versus Cloud Analysis and IDA: Different Methods to Evaluate Structural Seismic Fragility [Articolo su rivista]
Contiguglia, C. P.; Pelle, A.; Briseghella, B.; Nuti, C.
abstract

Well-known methods for seismic performance assessment, such as incremental dynamic analysis (IDA), multi-stripes analysis (MSA) and the cloud method, involve nonlinear response time-history analyses to characterize the relationship between the chosen damage measure versus intensity measure. Over the past two decades, many authors have proposed simplified procedures or nonlinear static approaches to develop fragility. In these procedures, the capacity of the system is evaluated by nonlinear static procedures (i.e., the capacity spectrum method (CSM), the N2 method, modal pushover analysis (MPA)) and the demand is derived by response spectra. In addition to the familiar ones, incremental modal pushover analysis (IMPA) is a novel nonlinear static procedure proposed in recent years, and it is used in this research to present an IM-based fragility estimation. The accuracy and effectiveness of different methods to assess vulnerability are investigated by comparing fragility curves derived by MPA-based cloud analysis, IMPA and cloud analysis against IDA. The comparison gives valuable insights on the influence of scaling on different sets of records; however, a more extended validation is needed to confirm the obtained results and draw more general conclusions. Results arise from two relatively small bins of record motions differing by ranges of Joyner-Boore distance and scattered in a range of magnitude are presented.

2022 - Mechanical performance of skewed deck-extension bridge [Relazione in Atti di Convegno]
Xue, J. Q.; Mao, S. R.; Briseghella, B.; Chen, B.; Miao, J. B.; Wang, X.
abstract

2022 - Numerical simulation and simplified calculation of the effective slab width for composite cable-stayed bridges [Articolo su rivista]
Giaccu, G. F.; Briseghella, B.; Fenu, L.
abstract

With the advent of progressively large and complex structures, the simultaneous presence of axial forces and bending on bridge decks is emerging as a recurring and increasingly concerning phenomenon. In the design of steel–concrete composite cable-stayed bridges, the combination of the axial force, mainly induced by the inclination of the cables, and bending is being increasingly considered to realize long spans that can bear the weight of the structure while ensuring a high rigidity of the deck. Despite its importance, this aspect is not sufficiently treated in the design codes, e.g., Eurocode specifications do not consider the axial force and its shear lag effects; therefore, the design rules are specified exclusively for the case of bending. From a practical standpoint, this deficiency can entail design complications due to the use of complicated FE models (shell and brick elements), which incur significant computational loads and design effort. In this study, a simple methodology for the design and verification of a girder composite deck subjected to combined compression and bending is developed. The methodology is based on a parametric study performed using finite element (FE) models that are valid for a generic girder composite deck. The stress distribution on the composite deck can be assessed while accounting for the axial force and bending moments associated with the deck by considering the results obtained using universal beam models. The proposed methodology is applied to an existing cable-stayed bridge.

2022 - Photocatalytic concrete for degrading organic dyes in water [Articolo su rivista]
Briseghella, Bruno
abstract

Since the advent of photocatalytic degradation technology, it has brought new vitality to the environmental governance and the response to the energy crisis. Photocatalysts harvest optical energy to drive chemical reactions, which means people can use solar energy to complete some resource-consuming activities by photocatalysts, such as environmental governance. In recent years, researchers have tried to combine photocatalyst TiO2 with building materials to purify urban air and obtained good results. One of the important functions of photocatalysts is to degrade organic pollutants in water through light energy, but this technology has not been reported in the practical application areas. To extend this technology to practical application areas, photocatalytic concrete for degrading pollutants in waters was proposed and demonstrated for the first time in this paper. The photocatalytic concrete proposed based on the K-g-C3N4 shows a strong ability to degrade the organic dyes. According to the experiment results, the angle of light source plays an important role in the process of photocatalytic degradation, while waters with pH value of 6.5–8.5 hardly influenced the degradation of organic dyes. When the angle of light source is advantageous for photocatalytic concrete to absorb more visible light, more organic dyes will be degraded by photocatalytic concrete. The degradation rate of methylene blue could reach about 80% in ½ hour under desirable conditions and is satisfied compared with that of reported works. This study implicates that photocatalytic concrete can effectively degrade organic dyes in water. The influences of changes in the water environment hardly affect the degradation of organic pollutants, which means photocatalytic concrete can be widely used in green infrastructures to achieve urban sewage treatment.

2022 - Probabilistic Assessment of a Light-Timber Frame Shear Wall with Variable Pinching under Repeated Earthquakes [Articolo su rivista]
Briseghella, Bruno
abstract

Pinching characterizes the hysteretic response of several structural systems. It is associated with a reduced dissipated hysteretic energy under cyclic loading and can significantly affect seismic performance, especially under repeated earthquakes. Although several scholars proposed advanced joint arrangements with reduced pinching, ordinary timber structures present pronounced pinching effects due to the local damage to the timber joints. This paper quantifies the impact of variable pinching on the seismic performance of a timber structural archetype. The authors modeled the hysteretic response of a light-timber framed assembly using an empirical hysteresis model and assessed the sensitivity of the displacement demand of the chosen archetype to pinching, number of earthquake repetitions, and spectral acceleration. The choice of an elementary structural archetype, rather than a more complex system, allows isolating the effects of pinching, which could otherwise be disguised by other phenomena, like force redistribution between structural assemblies due to plasticization.

2022 - Probabilistic axial capacity model for concrete-filled steel tubes accounting for load eccentricity and debonding [Articolo su rivista]
Contento, A.; Aloisio, A.; Xue, J.; Quaranta, G.; Briseghella, B.; Gardoni, P.
abstract

Concrete-filled steel tubular (CFST) columns are increasingly used around the world because they offer two significant advantages. The first one is the composite action of the steel tube and infilled concrete, which enhances the strength and ductility of the columns. The second one is the use of the steel tube as a permanent formwork for concrete casting, which allows saving construction time and costs. Although considerable research and several experimental tests have been carried out on CFST columns, there is not a probabilistic model for the evaluation of their axial capacity yet. Additionally, the effects of the axial load eccentricity and debonding have received little attention so far. Within this framework, the present paper proposes a physics-based probabilistic model to predict the ultimate axial capacity of CFST columns, which is developed as the sum of a deterministic part and a probabilistic correction term, together with two additional corrective models to describe its reduction due to load eccentricity and debonding, which are developed coherently with the axial capacity model as probabilistic correction terms. The accuracy of the proposed models is compared with that of existing capacity equations already in use within technical standards and available literature. Additionally, this study provides uncertainty factors to allow using the proposed capacity model for design applications. Thanks to their very good accuracy and compact form, the proposed models are suitable to be included within technical standards. On the other hand, differently from common deterministic models, they can also be updated as new experimental data are available. A case study with the derivation of fragility curves for a CFST bridge column shows a possible application and the advantages of the proposed model.

2022 - Quasi-static Test on Mechanical Behaviors of Pre-hole Isolation Pile-soil Interaction [Articolo su rivista]
Briseghella, Bruno
abstract

The heads of reinforced concrete (RC) piles are extremely easily damaged owing to the longitudinal deformations induced by the superstructures in integral abutment bridges (IABs) under temperature variations and seismic actions. The pre-hole isolation piles can be obtained by predrilling oversized holes (pre-holes) filled with damping materials. This can improve the seismic performance of RC piles in IABs. A pile beneath an abutment in an IAB was chosen as a case study. Quasi-static tests considering different pre-hole diameters and damping materials (rubber particles and foam) were carried out to analyze the mechanical behaviors of pre-hole isolation pile-soil interaction. When the loads reached the peak values, pile-sand separation was observed in the specimen without a pre-holes. Pile-damping material and damping material-sand separations were found in the specimens when the pre-holes diameter was two times the pile diameter. The horizontal displacement of the pile was completely absorbed by the deformation of rubber particles in the specimen with a pre-holes filled by rubber particles when the pre-holes diameter was three times the pile diameter. Therefore, the pre-holes diameter can be considered the parameter with the most influence on the transmission mode of pile horizontal displacement to the damping materials. Compared with the specimen without a pre-holes, the hysteresis loops of the pre-holes isolation specimens were larger, as were the equivalent viscous damping ratios. It can be concluded that the energy of the damping materials can be dissipated in the pre-holes isolation piles. The energy dissipation of the specimen with a pre-holes filled by rubber particles is stronger than that of one filled by foam. This is because the deformation capacity and automatic reset characteristics of the loose rubber particles can help energy dissipation; however, the viscosity and damping characteristics of the foam are influenced by its integrity. The stiffness of the p-y curves of the pre-holes isolation specimens within the pre-holes depth were significantly lower than those of the specimen without a pre-holes (maximum decrement of 45.1%). With an increase in the pre-holes diameter or a decrease in the stiffness of the damping materials, the soil modulus coefficients decrease. Compared with the specimen without a pre-holes, the ultimate load-bearing capacities of the pre-holes isolation specimens were slightly larger, and the initial stiffness and maximum bending moments along the piles were slightly smaller.

2022 - Research on Seismic Behaviors of RC Circular Pier with Longitudinal Rebar of Reduced Diameter and CFRP Wrap [Articolo su rivista]
Xue, J. -Q.; Lavorato, D.; Nie, S. -J.; Chen, J. -Z.; Briseghella, Bruno; Camillo, N.
abstract

Investigations on the seismic damage of bridges after earthquakes indicate that reinforced concrete (RC) piers are easily damaged, which influences the rescue and reconstruction after earthquakes. Repairing damaged piers with the technology, which substitutes the damaged original longitudinal rebar using a longitudinal rebar with a reduced diameter (turned rebar) and envelops the RC piers with the carbon fiber reinforced polymer (CFRP), can shorten the repair period after earthquakes and reduce the reconstruction costs. The RC circular pier in a continuous girder bridge with irregular piers was selected as the case study. Quasi-static tests on seven RC circular pier specimens with a reduced scale factor of 1: 6, considering the length and diameter of the turned rebar, and the layer of CFRP wrap as parameters were adopted. The finite element models were implemented using the OpenSees finite element software, and the accuracy was verified by the test results. Parametric analysis was performed using the finite element model. The results indicate that the plastic deformation of piers with the turned rebar was concentrated within its length, and the failure of piers was limited within the plastic hinge zone. Comparing the piers without the turned rebar, the load bearing capacity of piers with the turned rebar could decrease by 20%-27%; however, the displacement ductility, curvature ductility, and energy dissipation capacity increased by 42%-85%, 47%-242%, and 32%-56%, respectively. It was established that the turned rebar could effectively improve the seismic performance of piers when the load bearing capacity of piers satisfies the design requirements. The measured maximum strains of the CFRP wraps within the length of the turned rebar in the piers with the turned rebar, were significantly larger than those in the piers without the turned rebar. It can be concluded that the CFRP wraps could be chosen for piers with the turned rebar to prevent the premature failure of piers and improve the ductility. With an increase in the length of the turned rebar or a decrease in the diameter of the turned rebar, the energy dissipation capacity of the pier first increases and then decreases. Selecting the length of the turned rebar is proposed, considering the fatigue life of rebar as the lower limit and the length of the plastic hinge zone as the upper limit. The maximum diameter obtained, under the condition of ensuring that the stress of the longitudinal rebar outside the plastic hinge zone is always within the elastic range, can be considered as the diameter of the turned rebar. Using concrete with higher strength in the repair zone of the pier can increase the load bearing capacity of the pier with the turned rebar.

2022 - Seismic assessment of corroded concrete bridges using incremental modal pushover analysis [Articolo su rivista]
Briseghella, Bruno
abstract

An efficient yet accurate procedure has been developed for the seismic assessment of reinforced concrete bridges subject to chloride-induced corrosion. Specifically, the procedure involves using an incremental modal pushover analysis to assess corroded bridges as an alternative and less computationally demanding approach to non-linear dynamic analysis. A multi-physics finite-element analysis is performed to evaluate the effects of chloride-induced corrosion on bridge columns. In doing so, chloride ingress in concrete is numerically simulated as a discussion process by considering the effects of temperature, humidity, corrosion-induced cover cracking and concrete aging. The estimated chloride concentration is then employed to evaluate the corrosion current density, from which the effects of corrosion on reinforcement, cracked cover concrete, confinement and plastic hinge length can be determined for subsequent non-linear static analysis. A case study of a typical bridge structures is presented. The proposed procedure can be used to assess the seismic performance of irregular reinforced concrete bridges exposed to severe corrosive environments.

2022 - Simplified equivalent finite element modelling of concrete-filled steel tubular K-joints with and without studs [Articolo su rivista]
Ferrotto, M. F.; Fenu, L.; Xue, J. -Q.; Briseghella, B.; Chen, B. -C.; Cavaleri, L.
abstract

Concrete Filled Steel Tubular (CFST) K-joints employed for truss structures gained high interest in the last years due to their widespread use in engineering practice. The overall performances of these joints can be efficiently improved by using steel studs welded in the inner surface of the steel chord filled with the concrete, avoiding punching shear failure, and improving the overall strength and ductility. However, a reliable prediction of the structural behavior of the joints is outmost of importance for the assessment of the capacity of new and existing structures, and there are no standardized design methods nowadays. In this paper, the structural performances of CFST K-joints with and without steel studs are investigated by Finite Element Modelling (FEM) approach with the aim to provide a predictive tool for the design. A comprehensive discussion of the key parameters that govern the FEM procedure as well as the calibration of the FE models was provided to give the basis for a reliable modelling of CFST K-joints with and without studs for the predictions of the load–displacement/strain response and the strength, considering the main failure mechanisms. In this context, in addition to the detailed FEM of CFST K-joints with steel studs, a simplified equivalent FEM approach is proposed to reduce computational effort keeping the same accuracy.

2022 - Structural stress analyses of long-span railway extradosed cable-stayed bridge based on reasonable construction state [Relazione in Atti di Convegno]
Guo, W.; Briseghella, B.; Xue, J.; Chen, Q.; Nuti, C.
abstract

The system of the extradosed cable-stayed bridge constantly changed during construction. In order to obtain the reasonable finished dead state and ensure the structural safety during construction, it is necessary to deeply investigate the construction stages. A finite element model of a real long-span railway extradosed cable-stayed bridge built in China was established by using MIDAS/Civil finite element software to analyze the stress and deformation of the bridge based on reasonable construction state. The results show that it should be paid attention to the longitudinal displacement at the top of the tower after the middle-span closure stage, and the vertical displacement of the girder in the longest single cantilever stage. The maximum compressive stresses of the tower appeared after the cable tensioning and the girder appeared when the bridge is in the longest single cantilever state are less than the design compressive strength of concrete C55. The maximum tensile stress of the girder appeared when the bridge is in the longest double cantilever state is less than the design tensile strength of concrete C55.

2022 - Temperatures and gradients in concrete Bridges: Experimental, finite element analysis and design [Articolo su rivista]
Briseghella, Bruno
abstract

Aiming to introduce a simplified flexible design model for thermal actions in concrete bridge superstructures, experimental and finite element works were carried out in this study. From an experimental concrete box-girder segment, concrete temperature, solar radiation, air temperature and wind speed records for a complete one-year cycle were recorded and utilized. In addition, a thermal finite element model was conducted and verified, which was then used to conduct required parametric studies. Finally, the verified finite element model was used together with long-term climate history (from 1960 to 2013) of 10 cities in Turkey to propose the thermal actions' design models and procedure. Both positive and negative vertical temperature gradient models were introduced in terms of the top surface maximum temperature gradient, which is related to the solar radiation history of the region. In addition, simplified correlations and design procedure were suggested to evaluate the maximum and minimum mean temperatures of concrete bridges using the long-term maximum and minimum air temperatures.

2022 - Time-dependent cyclic behavior of reinforced concrete bridge columns under chlorides-induced corrosion and rebars buckling [Articolo su rivista]
Pelle, A.; Briseghella, B.; Bergami, A. V.; Fiorentino, G.; Giaccu, G. F.; Lavorato, D.; Quaranta, G.; Rasulo, A.; Nuti, C.
abstract

This study presents the results of a refined numerical investigation meant at understanding the time-dependent cyclic behavior of reinforced concrete (RC) bridge columns under chlorides-induced corrosion. The chloride ingress in the cross-section of the bridge column is simulated, taking into account the effects of temperature, humidity, aging, and corrosion-induced cover cracking. Once the partial differential equations governing such multiphysics problem are solved through the finite-element method, the loss of reinforcement steel bars cross-section is calculated based on the estimated corrosion current density. The nonlinear cyclic response of the RC bridge column under corrosion is, thus, determined by discretizing its cross-sections into several unidirectional fibers. In particular, the nonlinear modeling of the corroded longitudinal rebars exploits a novel proposal for the estimation of the ultimate strain in tension and also accounts for buckling under compression. A parametric numerical study is finally conducted for a real case study to unfold the role of corrosion pattern and buckling mode of the longitudinal rebars on the time variation of capacity and ductility of RC bridge columns.

2021 - A degrading bouc-wen data-driven model for the cyclic behavior of masonry infilled RC frames [Relazione in Atti di Convegno]
Pelliciari, M.; Sirotti, S.; Di Trapani, F.; Briseghella, B.; Marano, G. C.; Nuti, C.; Tarantino, A. M.
abstract

Mechanics-based macro-models are often used to simulate the cyclic response of infilled reinforced concrete (RC) frames. However, these approaches are affected by uncertainties regarding damage and failure mechanisms. Therefore, this contribution proposes a new smooth data-driven model for the hysteresis of infilled RC frames. The infill panel is modeled through a damage-based Bouc-Wen element, which accounts for both pinching and deterioration of the mechanical characteristics. The parameters of the model are calibrated from an experimental data set of cyclic responses of RC infilled frames. Analytical correlations between parameters and geometric and mechanical characteristics of the infilled frame are derived. Blind validation tests are carried out in order to demonstrate the effectiveness of the proposed model.

2021 - A resilience-based model for the seismic assessment of the functionality of road networks affected by bridge damage and restoration [Articolo su rivista]
Rasulo, A.; Pelle, A.; Briseghella, B.; Nuti, C.
abstract

Road network functionality after an earthquake is a crucial aspect for an already struck community. In particular, bridges are susceptible to earthquake-induced damages and to lengthy restoration works. This may lead to severe and unexpected disruption of traffic. In this paper, a model for the assessment of the seismic resilience of a road network is presented. The proposed model permits us to evaluate the earthquake-induced perturbations to the functionality of a network in terms of transportation capacities, traffic congestion, and travel times due to bridge damages and subsequent restoration interventions. The evolution over time of the functionality of the network is studied by means of a multi-stage approach describing the evolution of the situation in terms of reducing the normal pre-earthquakes transportation capacities. The methodology has been illustrated with reference to a hypothetical case study, a road network composed of 14 nodes and 31 links.

2021 - Bridge pier corrosion in seismic areas: Forecasting, future behavior and assessment (key-note lecture) [Relazione in Atti di Convegno]
Nuti, C.; Pelle, A.; Quaranta, G.; Bergami, A. V.; Briseghella, B.; Lavorato, D.; Fiorentino, G.; Rasulo, A.
abstract

The detrimental effect of steel corrosion on seismic response is investigated by non-linear analysis. A multiphysics FE model is used to evaluate the time-dependent chloride-induced corrosion. Different steel arrangements are considered. Results show that the greater is the diameter of the reinforcing bar, the lower is the degree of corrosion. Furthermore, numerical investigations of seismic response with IMPAb suggest that pitting corrosion may lead to different bar behavior, producing or avoiding premature bar buckling. Corrosion of transverse reinforcements results to be more severe than for longitudinal ones leading to probable shear failure.

2021 - Chinese high rise reinforced concrete building retrofitted with clt panels [Articolo su rivista]
Contiguglia, C. P.; Pelle, A.; Lai, Z.; Briseghella, B.; Nuti, C.
abstract

Cross laminated timber (CLT) panels have been gaining increasing attention in the construction field as a diaphragm in mid-to high-rise building projects. Moreover, in the last few years, due to their seismic performances, low environmental impact, ease of construction, etc., many research studies have been conducted about their use as infill walls in hybrid construction solutions. With more than a half of the megacities in the world located in seismic regions, there is an urgent need of new retrofitting methods that can improve the seismic behavior of the buildings, upgrading, at the same time, the architectural aspects while minimizing the environmental impact and costs associated with the common retrofit solu-tions. In this work, the seismic, energetic, and architectural rehabilitation of tall reinforced concrete (RC) buildings using CLT panels are investigated. An existing 110 m tall RC frame building located in Hui-zhou (China) was chosen as a case study. The first objective was to investigate the performances of the building through the non-linear static analysis (push-over analysis) used to define structural weaknesses with respect to earthquake actions. The architectural solution proposed for the building is the result of the combination between structural and architectonic needs: internal spaces and existing facades were re-designed in order to improve not only the seismic performances but also energy efficiency, quality of the air, natural lighting, etc. A full explanation of the FEM modeling of the cross laminated timber panels is reported in the following. Non-linear FEM models of connections and different wall configurations were validated through a comparison with available lab tests, and finally, a real application on the existing 3D building was discussed.

2021 - Comparison of Form-finding Methods to Shape Concrete Shells for Curved Footbridges [Articolo su rivista]
Congiu, E.; Fenu, L.; Briseghella, B.
abstract

Shells are attractive and efficient structures that play a special role for engineers and architects. However, only few bridges supported by concrete shells have been designed and built after the Musmeci’s bridge in Potenza (Italy). Several numerical form-finding methods have been implemented in the last decades to optimize the shape of shells. In the present paper, a comparison of the Thrust Network Analysis (TNA) and Particle-Spring System (PS) is made by searching the optimal shape of a concrete shell supporting the curved cantilevered deck of a pedestrian bridge under the same boundary conditions. Finite Element Analysis was performed to compare the structural behaviour of the footbridges optimized by the two different form-finding techniques. The effectiveness of both form-finding methods in minimizing unfavourable tensile stresses in concrete shells, thus taking advantage of mechanical properties of concrete, is investigated. Furthermore, transverse deflections of the curved cantilevered deck were reduced introducing an external prestressing system applied to the upper flange of the ring box girder. Finally, the obtained results can help architecture and engineering practitioners to develop innovative bridge conceptual design.

2021 - Development and Validation of New Bouc-Wen Data-Driven Hysteresis Model for Masonry Infilled RC Frames [Articolo su rivista]
Sirotti, S.; Pelliciari, M.; Di Trapani, F.; Briseghella, B.; Carlo Marano, G.; Nuti, C.; Tarantino, A. M.
abstract

During the last years, several mechanics-based macromodels have been proposed to assess the cyclic response of infilled RC frames. However, the uncertainties behind the assumptions on damage and failure mechanisms compromise the reliability of such approaches. For this reason, this paper proposes a new data-driven hysteresis model for the cyclic response of infilled RC frames. The infill panel is schematized as a single-degree-of-freedom element, whose constitutive law is given by the proposed hysteresis model. The model combines a degrading Bouc-Wen element with a slip-lock element, which is introduced specifically to reproduce the pinching effect due to crack openings in the masonry panel. The parameters governing the model have clear physical meanings and are calibrated on the basis of an experimental data set of cyclic responses of single-story single-bay RC infilled frames. The calibrations are carried out by means of a genetic algorithm-based optimization. Analytical correlation laws linking the model parameters with geometric and mechanical properties of the RC infilled frame are proposed and validated by blind validation tests. Results show adequate accuracy of the model in reproducing the cyclic response of infilled frames characterized by significantly different geometrical and mechanical features. The model is defined by a smooth analytical hysteresis law, with great advantages regarding numerical stability and computational effort. This makes it suitable for dynamic and stochastic simulations.

2021 - Durability analysis and environmental impact of ultra-high performance fibre reinforced concrete (UHPFRC) for bridge applications [Relazione in Atti di Convegno]
Nuti, Camillo; Pelle, Angelo; Quaranta, Giuseppe; Bergami, Alessandro V.; Briseghella, Bruno; Fiorentino, Gabriele; Lavorato, Davide; Rasulo, Alessandro
abstract

2021 - Dynamic characteristics of a curved steel–concrete composite cable-stayed bridge and effects of different design choices [Articolo su rivista]
Briseghella, Bruno
abstract

The paper presents and discusses the dynamic response of a curved cable-stayed bridge in Venice (Italy). Two distinct experimental campaigns in 2010 and 2011 led to identifying the bridge dynamic characteristics in operational conditions. The dynamic identification included the characterization of both the deck and cables response. The authors developed a highly refined finite element (FE) model of the bridge, mirroring up to twelve experimental modes. An updating procedure drove the estimate of the optimum parameters associated with the lowest discrepancy with the experimental modal parameters. The calibrated model was the base of a parametric analysis on the effects of the deck curvature, cables arrangement and tower cross-section inertia on the bridge dynamics. Specifically, the authors developed fourteen FE models of the bridge distinguished by the lack and different arrangement of the stay cables, the increasing value of the deck curvature and the tower cross-section inertia. The analysis intends to quantify the impact of the design choices of cable-stayed bridges on the modal parameters.

2021 - Effects of Excitation Bandwidth on Damping Reduction Factor [Articolo su rivista]
Greco, R.; Fiore, A.; Marano, G. C.; Briseghella, B.
abstract

In seismic codes, elastic response spectra are usually defined by adopting a conventional value for the damping ratio equal to 5%. Damping Reduction Factors (DRFs) are then introduced to account for the effect of damping values higher than the nominal 5%. In this framework, the main aim of the present study is to explore a new definition of DRF. The concept of stochastic response spectrum is used for predicting the earthquake response of a structural system by adopting the random vibration theory for nonstationary processes. The peak theory is finally used to determine the DRF.

2021 - Experimental study on SSI of flat buried approach slab in jointless bridge [Relazione in Atti di Convegno]
Xue, J. Q.; Tang, Y. F.; Briseghella, B.; Huang, F. Y.; Chen, B. C.; Nuti, C.
abstract

The deck joints between the bridge deck and approach slab can be eliminated in jointless bridges, which become more and more popular. The approach slab of jointless bridge can not only alleviate the differential settlement between the bridge deck and embankment, but also transfer and absorb the longitudinal thermal movement of the superstructure. The soil-structure interaction (SSI) between the approach slab and embankment soil is an important factor. The experimental tests on flat buried-typed approach slab (FBAS) considering SSI were carried out. With the increase of depth, the initial linear part, the nonlinear part and the second linear part the force-displacement curve was increased to varying degrees, and the deformation of soil surface in vertical direction were decreased and that in horizontal direction increased. Finally, some recommendations were proposed to optimize the behavior of FBAS. This analysis can provide a reference for the application of FBAS in jointless bridges.

2021 - Finite element thermo-mechanical analysis of concrete box-girders [Articolo su rivista]
Abid, Sr; Taysi, N; Ozakca, M; Xue, Jq; Briseghella, B
abstract

A full-scale 3D thermo-mechanical Finite Element (FE) model was conducted in this research to investigate the effect of open-field thermal loads on the structural response of box-girder bridges. A box-girder bridge with a span of 50 m was analyzed for temperature, radiation and displacement fields using COMSOL Multiphysics. To verify the FE model, a full-scale experimental box-girder segment was constructed and instrumented with temperature, radiation and other sensors. From the experimental records, three days with extreme temperature and radiation measurements were selected. The stresses and displacements are discussed at specific points along the 24 h of the selected days and at specific times along critical sections. The FE analysis showed that the vertical and lateral stress distributions exhibited approximately similar behaviors to their corresponding temperature distributions with minor differences but with reversed sign. The results also showed that the maximum stress was compressive, which was −3.35 MPa in summer −3.83 MPa in winter. On the other hand, the maximum vertical and lateral displacements were 12.5 and 1.2 mm, respectively in summer and 2.7 and 1.9 mm in winter.

2021 - Geometrical parametric study on steel beams exposed to solar radiation [Articolo su rivista]
Abid, Sr; Al-Gasham, Ts; Xue, Jq; Liu, Yj; Liu, J; Briseghella, B
abstract

A finite element thermal analysis was conducted in this study with the aim of evaluating the influence of the geometrical parameters of steel sections on their thermal response under solar radiation. Four W12 and W24 standard steel beams were investigated under the solar irradiation conditions of a sunny summer day. The finite element analysis was carried out using COMSOL Multiphysics considering the Sun’s movement from sunrise to sunset, reflected radiation from the ground, surface convection of air and long wave radiation as the main boundary thermal loads. The temperature-time variation at different locations in the sections, vertical temperature distributions, temperature gradient distributions and thermal stress distributions were investigated. The results showed that the daily maximum temperatures, temperature variation, temperature and temperature gradient distributions and thermal stresses are influenced by the geometry of the steel section. The flange width and flange thickness were found to be the controlling parameters during the noon hours, while these parameters in addition to web depth control the shading effect during the after-noon. On the other hand, web thickness affects the temperature of webs at sunrise and sunset times. Geometrical ratios like Wf/H, Wf/tf2 and 2Wf/Htf were the most influential parameters on tempera-tures, temperature gradients and thermal stresses of steel beams subjected to solar radiation. The investigated section with the maximum Wf/tf2 value of 0.96 (W12 × 58) recorded the highest top-surface noon temperature, while section W24 × 84 with the lowest Wf/tf2 value of 0.60 exhibited the lowest temperature.

2021 - Influence of pattern corrosion on the time-dependent cyclic behavior of RC bridge columns [Relazione in Atti di Convegno]
Pelle, A.; Briseghella, B.; Contiguglia, C.; Bergami, A. V.; Fiorentino, G.; Giaccu, G. F.; Lavorato, D.; Quaranta, G.; Rasulo, A.; Nuti, C.
abstract

This study is meant at understanding the influence of the pattern of corrosion due to chlorides-induced corrosion on the time-dependent cyclic behavior of reinforced concrete (RC) bridge columns. The chloride ingress in the cross-section of the column is simulated by a multiphysics FE approach taking into account both environmental and material factors. The non-linear cyclic responses of the RC bridge column under corrosion is evaluated by a nonlinear fiber model. A parametric study is finally conducted for a real case study, which aims at unfolding the role of the corrosion pattern on the time variation of capacity and ductility.

2021 - Integral abutment bridges: Investigation of seismic soil-structure interaction effects by shaking table testing [Articolo su rivista]
Fiorentino, G.; Cengiz, C.; De Luca, F.; Mylonakis, G.; Karamitros, D.; Dietz, M.; Dihoru, L.; Lavorato, D.; Briseghella, B.; Isakovic, T.; Vrettos, C.; Topa Gomes, A.; Sextos, A.; Nuti, C.
abstract

In recent years there has been renewed interest on integral abutment bridges (IABs), mainly due to their low construction and maintenance cost. Owing to the monolithic connection between deck and abutments, there is strong soil-structure interaction between the bridge and the backfill under both thermal action and earthquake shaking. Although some of the regions where IABs are adopted qualify as highly seismic, there is limited knowledge as to their dynamic behaviour and vulnerability under strong ground shaking. To develop a better understanding on the seismic behaviour of IABs, an extensive experimental campaign involving over 75 shaking table tests and 4800 time histories of recorded data, was carried out at EQUALS Laboratory, University of Bristol, under the auspices of EU-sponsored SERA project (Seismology and Earthquake Engineering Research Infrastructure Alliance for Europe). The tests were conducted on a 5 m long shear stack mounted on a 3 m × 3 m 6-DOF earthquake simulator, focusing on interaction effects between a scaled bridge model, abutments, foundation piles and backfill soil. The study aims at (a) developing new scaling procedures for physical modelling of IABs, (b) investigating experimentally the potential benefits of adding compressible inclusions (CIs) between the abutment and the backfill and (c) exploring the influence of different types of connection between the abutment and the pile foundation. Results indicate that the CI reduces the accelerations on the bridge deck and the settlements in the backfill, while disconnecting piles from the cap decreases bending near the pile head.

2021 - Numerical analyses on flexural performance of prefabricated UHPC link slab [Relazione in Atti di Convegno]
Briseghella, B.; Xu, W.; Xue, J. -Q.; Lin, J. -H.; Nuti, C.
abstract

The expansion joints in the multi-span simply supported bridge can be eliminated by using the link slab. The ultra-high performance concrete (UHPC) with high tensile strength and crack resistance is an effective material for the link slab. However, the cast-in-situ UHPC link slab need to be cured with steam curing. Therefore, the construction processes are complicated and the construction quality is difficult to guarantee. In this paper, the prefabricated UHPC link slab which can be assembled on site to simply the construction process, accelerate the construction speed and reduce the labor cost was proposed. Finite element models of the prefabricated and cast-in-situ UHPC link slabs under bending were built by using ABAQUS. The ultimate bearing capacity of the prefabricated link slab was nearly the same of the cast in situ and the crack resistance slightly lower. Finally, the influence of the bolt (used to connect the prefabricated link slab) number and the distance from the bolt to the edge of the link slab on the crack resistance and ultimate bearing capacity of the prefabricated link slab were obtained.

2021 - Numerical analyses on mechanical performance of flat buried approach slab and soil deformation [Relazione in Atti di Convegno]
Briseghella, Bruno
abstract

The vulnerability problem of expansion joints could be fundamentally resolved using the concept of jointless bridges. The longitudinal deformation of the superstructure can be transferred to the backfill by using the approach slab. The flat buried approach slab (FBAS) has been used in many jointless bridges in European countries. In order to understand the mechanical performance of FBAS and soil deformation, a finite element model (FEM) was implemented in PLAXIS. Considering the friction between the FBAS and soil, the buried depth, the FBAS length and thickness as parameters, a parametric analysis was carried out. According to the obtained results and in order to reduce the soil deformation above the FBAS, it is suggested to increase the friction between the FBAS and sandy soil, and the buried depth of FBAS. Moreover, it should be paid attention to the vertical soil deformation and the concrete tensile stress of FBAS in pulling condition.

2021 - Optimum damping of slender monopole towers by gyroscopic stabilizer [Relazione in Atti di Convegno]
Giaccu, G. F.; Fenu, L.; Briseghella, B.; Nuti, C.
abstract

Slender structures as lighting poles and telecommunication towers are usually very sensitive to wind effects due their dynamic characteristics and due to their notable exposure to wind forces. Wind-induced forces produce fluctuating stress, which, despite the assessment of dynamic properties and the study of the environmental conditions, can lead to damage accumulation and consequent collapse of these structures. Careful attention to wind forces has, therefore, to be paid for these typologies of structures, since several damages have been attributed to fatigue issues. It is well known that damping and structural frequencies play a fundamental role in the structural response under wind loads; in fact, an increase of damping would lead to remarkable beneficial effects on the dynamic response of these structures. This paper focuses the attention on a mathematical model of a damped gyroscopic device conceived as a dynamic stabilizer for such slender structures; the proposed mechanical device allows for an increase of structural damping with a consequent improvement of dynamic performances of the tower subjected to wind loads. A parametric study for different mechanical properties of the gyroscopic device has been conducted in the present paper aiming to assess the effectiveness of the proposed apparatus for different configurations of the proposed device.

2021 - Optimum design of a hybrid isolation device for server racks using constrained differential evolution algorithm [Relazione in Atti di Convegno]
Aceto, L.; Quaranta, G.; Camata, G.; Briseghella, B.; Spacone, E.
abstract

Nonstructural elements and contents often constitute a large fraction of the economic investment in ordinary buildings. In case of seismic events, damage to nonstructural elements not only contributes to the overall direct material costs but can also significantly impact the indirect costs. The latter are especially affected by earthquake-induced damage if production and business flows depend on proper functioning of such nonstructural components, since consequent downtime costs turn out to be very high. Within this framework, server racks' performance under seismic loading is of interest in the present work. The economic relevance of these nonstructural components requires the implementation of proper design solutions so that their performance under earthquakes can fulfill specific requirements. In this perspective, including isolation devices between server racks and building floors is deemed effective for enhancing the stability of the protected equipment, preserving the computer components' integrity and, minimizing downtime losses. Hence, the present work is meant to optimize a hybrid isolation system for server racks. Specifically, the hybrid isolation device designed for such application combines at least two elastomeric isolators and three sliders, and it is intended for the seismic protection of server racks characterized by different configurations. The objective function is formulated to minimize the accelerations transmitted to server racks and manufacturing cost.

2021 - Optimum design of piles with pre-hole filled with high-damping material: Experimental tests and analytical modeling [Articolo su rivista]
Briseghella, Bruno
abstract

The piles represent the most vulnerable structural components in Integral Abutment Bridge (IAB). They must adsorb the thermal deformation and the seismic loading transferred from the superstructure to the substructure. The use of pre-holes filled with high-damping material represents a possible solution for enhancing the dissipative performance of reinforced concrete (RC) piles in IABs. This paper presents the experimental tests of four RC pile specimens backfilled with different damping material to assess their effect on the soil-structure hysteretic response. The authors developed a physical hysteresis model of the soil-pile interaction to assess the optimum length of the damping pre-hole. Firstly, the model is calibrated to the experimental tests. Then the authors extrapolated the hysteresis models to full-scale specimens to estimate their optimum design in practical applications.

2021 - Physical model of an Integral Abutment bridge: Numerical and experimental analyses [Relazione in Atti di Convegno]
Briseghella, Bruno
abstract

Integral Abutment Bridges (IABs) are characterized by the absence of bearing supports and expansion joints between the deck and the abutments/piers, thus reducing the construction and maintenance costs of these structures. This type of connection leads to more complex Soil-Structure Interaction (SSI) with respect to conventional bridges, therefore the static and dynamic effects of the SSI should be taken into account in the design. Despite the large number of IABs worldwide, and the numerical studies about them, only few experimental tests were performed and, moreover, there is a lack of design prescriptions in seismic codes including Eurocodes. This work presents results regarding the experimental campaign carried out at the EQUALS-BLADE Laboratory of the University of Bristol under the auspices of SERENA-SERA-TA Project, featuring shaking table tests on a scaled physical model of a single span IAB, tested into a large shear soil container to reproduce natural soil conditions and simulate the SSI between the abutments and the backfill soil. Different configurations were tested, varying i) the type of connection between the abutment footing (connected and disconnected) and ii) the introduction of one or more layers of a compressible inclusion material between the abutments and the backfill soil.

2021 - Prediction of ultimate load capacities of CFST columns with debonding by EPR [Articolo su rivista]
Xue, J. -Q.; Fiore, A.; Liu, Z. -H.; Briseghella, B.; Marano, G. C.
abstract

Concrete filled steel tubular (CFST) structures have become a viable alternative to reinforced concrete or steel structures due to several advantages. One of the most important is the confinement effect of the concrete core provided by the steel tube. However, this beneficial composite action will be probably weakened by debonding, so reliable formulations to predict the reduced ultimate resistance are needed. In this paper, a review of existing specifications and experimental tests carried out on compressed circular CFST columns with and without debonding, is given. Accordingly, more circular CFST long specimens with debonding should be necessary to understand the combined influence of slenderness ratio, load eccentricity ratio and confinement factor on the reduction coefficient (KD) of ultimate load capacities (Nu). The combined influence of arc-length ratio and thickness of circumferential debonding gap on KD should be further studied by experimental tests. Moreover, the existing formulae for KD and Nu show a low accuracy in predicting the test results and should be improved. To this aim, an evolutionary polynomial regression (EPR) MOGA-based methodology was performed to obtain more accurate formulations for Nu and KD of circular CFST columns with debonding. The formulae extracted from the Pareto front of non-dominated solutions, demonstrate good accuracy, higher than the ones in literature. The proposed models are consistent with the physical interpretation of the studied phenomenon according to which Nu and KD decrease as debonding parameters increase and can be used to calculate the real resistance of CFST structures.

2021 - Pseudo-static test on mechanical behavior of pile with pre-hole filled by rubber particles [Relazione in Atti di Convegno]
Briseghella, B.; Fu, R. H.; Xue, J. Q.; Lin, Y. B.; Huang, F. Y.; Nuti, C.
abstract

Integral abutment bridges (IABs) could fundamentally resolve the durability problems of expansion joints and bearings in bridges with expansion joints and improve the seismic performance due to high redundancy and integrity. The concrete piles beneath abutments were considered as the most vulnerable component in IABs under longitudinal deformation of superstructure caused by the temperature variation and seismic load. The pre-hole method was adopted by researchers to absorb the longitudinal deformation transferred from superstructure to the piles. Therefore, how to improve the seismic resistance of concrete piles is the key issue in IABs. In this paper, the piles with pre-hole filled by damping materials in IABs was proposed. The pseudo-static test of three pile specimens with the scaled factor of 1/12.5 and different pre-hole dimensions was carried out. The rubber particles were chosen as the damping material. It can be observed that comparing with the pile specimen without pre-hole, the hysteresis loops of the pile specimens with pre-hole filled by rubber particles were plumper and the equivalent viscous damping ratios were larger. The pre-hole diameter calculated from the pile central point is one of the key parameters which can influence the horizontal displacement transmission of piles to the rubber particles and sand. The influence of pre-hole filled by rubber particles on the failure mode, horizontal displacement and bending moment of the piles were not obvious. Consequently, the method of pre-hole filled by rubber particles could improve the energy dissipation and seismic performance of the concrete piles in IABs.

2021 - Research on dynamic characteristics and seismic performance of jointless bridges [Articolo su rivista]
Guo, W. -Q.; Briseghella, B.; Xue, J. -Q.; Luo, X. -Y.; Huang, F. -Y.; Wei, B.
abstract

A simply supported girder bridge built in Fujian Province was taken as a research background. The bridge was transformed into a semi-rigid integral bridge in the practical engineering. On the basis, the original bridge would be transformed into an integral bridge, semi-integral bridge, and extended-deck bridge. The finite element models of five bridges were built based on the MIDAS/Civil software. The differences of their mechanical performances under the seismic load were analyzed.The results show that the simply supported girder bridge is easy to cause the girder to fall at the abutment, while the jointless bridges can effectively prevent the occurrence of the phenomenon. The integral bridge shows a better seismic performance and is more suitable for building in the high earthquake areas. The effective lengths of piles of the jointless bridges and simply supported girder bridge are at the buried depths of 0-10D(D is the pile diameter). The pile of integral bridge has a good mechanical performance under the large seismic load, which can be better for protecting the pile foundation from damage. The mechanical behaviors of the pile at the abutment bottom of the extended-deck bridge and simply supported girder bridge are similar. Therefore, the design of the extended-deck bridge can refer to the design code of the traditional seam bridge. In addition, it is also found that the bending moment at the pier bottom is the largest in both the jointless bridges and simply supported girder bridge, and the plastic hinges can be easily formed at the position. Under the action of longitudinal seismic load, the most unfavorable positions of mechanical behaviors of girders of the simply supported girder bridge and extended-deck bridge are respectively appeared at the mid-span and pier top, while those of the integral bridge, semi-rigid integral bridge and semi-integral bridge are appeared at the abutment top. More attention should be paid to these positions in the design. The research results can provide a reference for the design of jointless bridges and formulation of related codes.

2021 - Research on mechanical behaviors of multi-span jointless bridge with link slabs over piers and abutments [Relazione in Atti di Convegno]
Xue, J. Q.; Lin, J. H.; Briseghella, B.; Huang, F. Y.; Nuti, C.
abstract

Deck joints are commonly used to accommodate the thermal movements of the superstructure. However, deck joints easily cause deterioration due to the leakage. One kind of jointless bridge with link slabs over the piers and abutments which could eliminate all deck joints was taken into account in this paper. Finite element models of three bridge types including bridge with deck joints over the piers and abutments, bridge with link slabs only over the piers, and bridge with link slabs over the piers and abutments were built by MIDAS-CIVIL to study their mechanical behaviors. The results showed that bridge with link slabs can retain the mechanical behaviors of simply supported girder bridge, but secondary internal force would be increased by temperature effect. The link slab over the piers and abutments could reduce the vertical deflection and the stress of girders under vehicle load, which can increase the smoothness of bridge deck and improve the driving comfortableness. But due to the earth pressure behind the abutments under uniform temperature variation, the secondary internal force, the vertical deflection and stress of girder and link slab would be increased in bridge with link slabs over the piers and abutments.

2021 - Seismic performance of Pakistani-technique infilled reinforced concrete frames [Relazione in Atti di Convegno]
Khan, N. A.; Bergami, A. V.; Nuti, C.; Monti, G.; Vailati, M.; Briseghella, B.
abstract

Infilled reinforce concrete (IRC) frames are commonly built across the world. Modern building codes address the influence of infill walls in seismic design and assessment of existing structures. Other building codes commonly consider infill walls as non-structural elements and do not require any explicit verification. One of such codes is the Pakistan Building Code (PBC), which does not foresee recommendations and guidelines for IRC frame structures, despite being a common construction typology in the Country. Records of past earthquakes show that infill types and material properties strongly affect the seismic response of buildings thus highlighting the importance of such parameters and making the topic worth investigating in detail. This paper introduces a numerical model for infill walls, which predicts different features of the nonlinear response, such as cracking, peak force, failure and residual force. Such features are expressed as function of infill friction coefficient between mortar and brick surface and mortar strength, whose effects are commonly neglected in available numerical models. The model is applied to a comprehensive case study of a three-story IRC frame factory building, located in the city of Mirpur, Pakistan, hit by an earthquake of magnitude 5.9 on 24 September 2019. The results obtained the model show good agreement with the observed in-situ damage patterns, thus revealing the importance of correctly modeling the infill walls when seismically designing and assessing Pakistani IRC buildings.

2021 - Simplified Method to Calculate Average Cross-Section Temperature of Small Box Girder under Extreme Climate Conditions [Articolo su rivista]
Briseghella, Bruno
abstract

Temperature variation can trigger longitudinal expansion and contraction deformation of the main girder of concrete bridges. To accurately predict the deformation, methods to calculate the average cross-section temperature of the main girder of bridges of such type were studied. A finite element model was established by MIDAS, taking a concrete small box girder bridge as the prototype bridge. The temperature field of the bridge was simulated and the peak average cross-section temperatures of the small box girder under extreme climate conditions were calculated. Two simplified methods to calculate the average temperature of the girder are proposed, one taking into account the peak ambient temperatures and the maximum daily solar radiation (Method 1) and the other considering the peak average daily temperatures on a monthly basis and the maximum daily solar radiation (Method 2). The results indicate that the finite element model built can accurately simulate the actual temperature field of the structure. It is suggested that the peak average cross-section temperature under extreme climate conditions be used to predict the main girder longitudinal expansion and contraction deformation of concrete bridge triggered by temperature variation. The peak average cross-section temperature of small box girder is in positive linear relation with the peak ambient temperature. Method 1 can generate accurate prediction, but a little complex. For the ease of calculation, Method 2 is a better choice, but the accuracy is not as good as Method 1.

2021 - Structural optimization of composite steel trussed-concrete beams [Articolo su rivista]
Briseghella, Bruno
abstract

The present work deals with the structural optimization of self-supported Composite Steel Trussed-Concrete Beams (CSTCB). CSTCB belongs to the category of prefabricated steel truss embedded in a concrete core casted in situ. The truss is typically composed of a steel plate, which represents the bottom chord, a system of diagonal bars and some coupled rebars working as upper chord. Optimized geometries lead to the minimization of material use. This results in the minimization of the costs, the achievement of sustainability targets, the reduction on the self-weight as well as many architectural advantages. At this purpose, a MATLAB code is herein presented. The code aims to optimize the geometry of the beam by means of a genetic algorithm (ga). Two different operative phases, before and after the concrete hardening, which characterize the mechanical response of the beam, are considered within the code. In addition, a case study is developed showing the application of the Matlab code to a homogenized prismatic beam. Advances beyond the state of the art are therefore shown.

2021 - Structural robustness of an RC pier under repeated earthquakes [Articolo su rivista]
Aloisio, Angelo; Pelliciari, Matteo; Alaggio Camillo Nuti, Rocco; Fragiacomo, Massimo; Briseghella, Bruno
abstract

The seismic resilience of structures and infrastructures is affected by damage accumulation phenomena, mainly related to the type of hysteresis. Specifically, pinching drives the cyclic response of several building materials, like reinforced concrete and masonry. Structural systems affected by pinching phenomena are prone to exhibit a dramatic increment of their displacement response after multiple cycles (repeated earthquakes, e.g.). The authors estimate a reinforced concrete pier's response using truncated incremental dynamic analysis by concatenating three earthquake scenarios. The authors adopted a Bouc-Wen class hysteresis model to simulate the reinforced concrete pier's cyclic response, matching its experimental cyclic response. The current analysis proved that ductility and resistance primarily drive the seismic response after a single earthquake. However, the performance after multiple earthquakes strongly depends on the pinching, degradation and drift accumulation, generally neglected in standard design practices.

2021 - The Impact of Corrosion on the Seismic Assessment of Reinforced Concrete Bridge Piers [Relazione in Atti di Convegno]
Rasulo, A.; Pelle, A.; Quaranta, G.; Lavorato, D.; Fiorentino, G.; Nuti, C.; Briseghella, B.
abstract

Reinforced Concrete (RC) bridges are a key elements for any transportation network, so that their safety and serviceability is of crucial importance especially after the occurrence of a seismic event. Frequently, RC bridges are exposed to the action of aggressive chemicals, such as in marine or in cold climate environments, for the presence of chloride ions, either due to the salty water or the use of deicing salt. Generally those aggressive environmental actions affect the steel rebars inducing corrosion phenomena with a degradation the mechanical properties of reinforcement. In this paper some modeling issues related to corroded RC piers are presented and discussed, with particular emphasis to their seismic assessment.

2021 - Time-Dependent Analysis of Precast Segmental Bridges [Articolo su rivista]
Giaccu, G. F.; Solinas, D.; Briseghella, B.; Fenu, L.
abstract

Prestressed segmentally constructed balanced cantilever bridges are often subjected to larger deflections than those predicted by calculations, especially for long-term effects. In this paper, the case of modular balanced cantilever bridges, which are prestressed segmental bridges obtained through a repetition of the same double cantilever, is investigated. The considered bridges are two typical cases of modular balanced cantilever both subjected to large deformations during their lifetime. In this case, due to the unusual employed static scheme, creep deflections indefinitely evolve over time particularly at the end of the cantilevers and in correspondence with the central joint. These remarkable deflections cause discomfort for vehicular traffic and in certain cases can lead to the bridge collapse. Important extraordinary maintenance interventions were necessary to restore the viability of the bridges and to replace the viaduct design configuration. To this aim, the static schemes of the structures were varied, introducing new constraints, new tendons, and carbon fiber reinforcements. In the present work, time analysis was performed to compare the time-dependent behavior of the bridge according to two different creep models, the CEB-FIP Model Code 2010 and the RILEM Model B3, with the real-time-dependent behavior of the bridge observed during its lifetime. The two different employed models exhibit different behaviors in terms of displacements and bending moments acting on the bridge. Interesting considerations are made on their reliability in simulating the long-term creep effects that evolve indefinitely over time. Moreover, retrofitting techniques have been proposed and modeled to predict their effectiveness in reducing time-dependent deflections.

2021 - Ultra-High performance concrete (UHPC) with polypropylene (Pp) and steel Fibres: Investigation on the high temperature behaviour [Articolo su rivista]
Briseghella, Bruno
abstract

Ultra-high performance concretes (UHPC) are advanced cement-based materials characterised by superior mechanical properties with respect to normal and high-strength concretes; however, their dense and compact matrix can facilitate the onset of spalling at high temperatures. This problem is often coped up by adding polypropylene (PP) fibres to the mix design, alone or with other types of fibres; steel fibres enhance the material's tensile capacity. The paper presents a series of tests on two UHPC types (150 and 180 N/mm2) with PP fibres (0.27% of volume) and variable content of steel fibres (0% to 1.92%), aimed at investigating the residual mechanical properties of the material after high temperature exposure. The experimental results are compared to available research on small UHPC specimens exposed to high temperatures, with dosages in PP fibres from 0.03% to 2%, and in steel fibres from 0 to 3%. The results of this research demonstrate that UHPCs need hybrid fibre reinforcement (PP + steel) to withstand high temperatures, and that the residual strength increases after 200 °C exposure, at all steel fibre dosages; this is in line with literature. Available research also shows that strength loss is possible in hot conditions, as found in the present research, while PP fibres alone do not always prevent the occurrence of spalling in small UHPC samples.

2020 - A corrosion model for the interpretation of cyclic behavior of reinforced concrete sections [Articolo su rivista]
Lavorato, D.; Fiorentino, G.; Pelle, A.; Rasulo, A.; Bergami, A. V.; Briseghella, B.; Nuti, C.
abstract

A generalized cyclic steel model characterized by isotropic and kinematic hardening, inelastic buckling in compression and corrosion of rebars in reinforced concrete (RC) structures is presented. The model has been implemented in a fiber code, to perform seismic analyses of RC sections. The model is particularly accurate with respect to experimental cyclic behavior of rebars with buckling in compression when the strain does not exceed 1.5%. Twelve configurations of RC cross sections were selected as case studies for three geometries and different steel arrangements, assumed representative of RC columns or bridge piers (in a suitable scale). Each section was subjected to two groups of cyclic curvature histories representative of severe seismic loads, not far from collapse. Different axial loads and corrosion percentages (no corrosion, moderate, or high) have been selected to perform cyclic parametric analyses. One of the cases was taken from an experimental test on columns, deriving also steel characteristics used in all numerical cases. The results of the comparison among RC sections have been discussed. Numerical results show that the maximum compressive strain for steel rebars is always smaller than 1.5%, therefore the proposed steel model is accurate and represents a valid tool for structural assessment. Corrosion reduces RC section capacity, affecting various rebar mechanical characteristics, in particular buckling behavior.

2020 - A degrading Bouc–Wen model for the hysteresis of reinforced concrete structural elements [Articolo su rivista]
Pelliciari, Matteo; Briseghella, Bruno; Tondolo, Francesco; Veneziano, Luigi; Nuti, Camillo; Greco, Rita; Lavorato, Davide; Tarantino, A. M.
abstract

This paper presents a smooth hysteresis model for reinforced concrete (RC) structural elements based on the differential equation of the Bouc?Wen model. Stiffness degradation and strength degradation are defined by introducing a damage index that includes both dissipated energy and maximum displacement. The pinching effect acts directly on the stiffness of the system and is controlled by an activation energy. The degrading functions are connected to the actual processes with which the damage occurs, thereby giving each parameter a physical meaning. The simple formulation of the model allows a straightforward identification of the best-fitting parameters and an easy interpretation of the results. Applications to the cyclic behaviour of RC structural elements demonstrate that the model is well capable of describing complex hysteretic behaviours involving degradation and pinching effects.

2020 - An iterative multilevel updating scheme for vibration-based damage assessment of a prestressed concrete girder bridge [Relazione in Atti di Convegno]
He, L.; Reynders, E.; Deng, C.; Marano, G. C.; Briseghella, B.; De Roeck, G.
abstract

For vibration-based structural health monitoring, a multilevel optimization scheme is applied to damage assessment of a prestressed concrete bridge. As a linear elastic problem to be addressed, damage was represented by reduction of structural stiffness of the reference model for the elements where the damage occurred. The Finite Element (FE) model updating problem is formulated as a nonlinear least-squares problem, which tries to minimize the differences between the reference model and the real (or simulated) structure with respect to the modal data. Due to the specific structure of the bridge, damage parametrization was introduced both using substructuring and a damage function. Consequently, the optimization variables were divided into global ones and local ones, which leads to the implementation of an iterative multilevel updating scheme. Satisfactory results were obtained for two numerical simulated damage scenarios: one with a single damage and one with multiple damage.

2020 - Analysis of dynamic characteristics of long-span railway extradosed bridge [Relazione in Atti di Convegno]
Guo, W.; Briseghella, B.; Xue, J.; Luo, X.; Chen, Q.; Huang, F.
abstract

In order to ensure the safety and reliability of the mechanical performance of the whole bridge in the operation stage of the completed bridge, this paper takes an Extradosed bridge, Panzhihua Jinshajiang bridge of Chengdu-Kunming Railway, as the research background, analyzes and studies the longitudinal resonance dynamic characteristics of the short tower cable-stayed bridge structure when the train load acts on the main beam under the condition of completed bridge. The longitudinal vibration of the main girder caused by live load will directly affect the safety and use of the expansion joint device at the abutment, and the damage of the expansion device will lead to the safety and reliability of vehicles in the later operation stage. The dynamic response of the structure caused by the different speed of live load is analyzed. The results show that when there is no significant difference between the live load action speed and the estimated longitudinal bridge resonance speed, there is no significant difference between the longitudinal bridge loading frequency when the live load passes through the bridge and the first-order longitudinal vibration frequency of the bridge. A longitudinal resonance phenomenon can be observed in Jinshajiang bridge, in which the dynamic response of the main beam and the main tower is obvious.

2020 - Application of the incremental modal pushover analysis to bridges subjected to near-fault ground motions [Articolo su rivista]
Briseghella, Bruno
abstract

Near-fault events can cause severe damage to civil structures, including bridges. Many studies have demonstrated that the seismic assessment is not straightforward. Usually, dealing with near-fault ground motion, the structural analysis is performed using Nonlinear Response-History Analysis (NRHA) but in the last years, many authors have tested existing pushover-based procedures originally developed and validated using far-field events. Between those procedures, the Incremental Modal Pushover Analysis (IMPAβ) is a pushover-based procedure specifically developed for bridges that, in this work, was applied to a case study considering near-fault pulse-like ground motion records. The records were analyzed and selected from the European Strong Motion Database. In the paper the results obtained with IMPAβ together with other standard pushover procedures, are compared with NRHA and incremental dynamic analyses; the vertical component of the motion has been also considered. Results obtained with the bridge case study demonstrate that the vertical seismic action has a minor influence on the structural response and that IMPAβ is confirmed as a very effective pushover-based method that can be applied also for near-fault events.

2020 - Chinese high rise reinforced concrete building retrofitted with CLT Panels [Relazione in Atti di Convegno]
Contiguglia, C. P.; Bergami, A. V.; Fiorentino, G.; Lavorato, D.; Nuti, C.; Lai, Z.; Briseghella, B.
abstract

CLT panels are becoming a widespread structural solution in the realization of new timber structures and, besides, they can be adopted for seismic retrofitting of existing structures such as Reinforced Concrete (RC) frame buildings. Moreover, the use of CLT panels can improve the energetic efficiency as well as other architectural parameters of an existing structures. In this work, an existing 100m tall RC frame-wall building located in Huizhou, China, was chosen as case study. The aims of the study were: 1) analyzing the structural performances of the building, without retrofitting, by means of a nonlinear pushover analysis in order to define structural weaknesses with respect to earthquake actions; 2) propose an architectural solution, where timber panels were positioned in a rational way with respect to architectural functions; therefore re-organizing the internal space and re-designing the existing facades. 3) verify the new structural performances after retrofitting with CLT panels.Additionally, studies on the energy efficiency, quality of the air, natural lighting were performed.

2020 - Comparative study on seismic design and check of piers by Chinese and European Codes [Relazione in Atti di Convegno]
Briseghella, Bruno
abstract

The function of bridges would be significantly influenced by the damage of piers during the earthquake, which would affect the rescue and reconstruction after the earthquake. Therefore, it is of great significance to carry out the comparative study on the seismic design and check of piers by the Chinese and European codes. The results show that the seismic design concepts of piers in the Chinese and European codes are the same. The behaviour factor and the seismic importance factor are used to reduce the seismic action in the European code and the Chinese code, respectively. For the check of shear capacity, the contributions of stirrups and concrete are separately considered in the European code, while they are simultaneously considered in the Chinese code. The steel weight of the pier designing by using Chinese codes is lower than that using European codes. The requirement on the minimum transverse reinforcement ratio in the European code is higher than that in the Chinese code.

2020 - Design of a base isolated timber building in the historical center of a high seismic hazard area of Italy [Relazione in Atti di Convegno]
Briseghella, Bruno
abstract

This paper deals with the design of an innovative school building under construction in the historical center of Ariano Irpino (Italy). The building has been designed to be integrated into the historical Town, with very peculiar and innovative structural aspects. The very characteristic heritage location, with small access roads and typical historical buildings, and the site topography, at the top of the hill characterized by sloping sides and high retaining structures, with high seismic hazard, strongly influenced the structural and architectonical solution. In order to deal with the site complexity, and realize a sustainable building, the designers developed an innovative solution: the substructure is a reinforced concrete (r.c.) volume on three sides underground, the superstructure is composed by a couple of timber buildings. Between the base and the timber buildings a base isolation system is placed (which results above the third floor of the complex). The use of cast onsite concrete offer an optimal solution for the basement, with the multiple function of soil retaining system, foundation and location for several fundamental functions (gym, conference hall and restaurants), whereas the use of timber frames and Cross-Laminated Timber (CLT) elements, for the buildings in elevations, allows to obtain a low energy consumption and eco-sustainability, not requiring big construction machines, notwithstanding the use of prefabrication. In this paper the architectural and structural solutions are presented discussing functionality, safety and sustainability issues.

2020 - Dynamic Characterization of a Stress Ribbon and Butterfly Arch Pedestrian Bridge Using Wireless Measurements [Relazione in Atti di Convegno]
He, L.; Zhang, Z.; Marano, G. C.; Briseghella, B.; Xue, J.; Ni, Z.
abstract

For their aesthetic values, both arches and stress-ribbon decks are widely used in design of pedestrian bridges. The combination of the two systems provides the solution of a self-anchored structure. In the current paper, the dynamic characteristics of a short-span stress ribbon and butterfly arch bridge are investigated by means of operational modal analysis. Ambient vibration of the bridge is recorded by using several highly-synchronous three-axial wireless accelerometers deployed on the bridge deck. Modal parameters, including natural frequencies, mode shapes and damping ratios are extracted from the measurements. By comparing the experimental modal results to their numerical counterparts obtained from a preliminary finite element model, interesting results are found both related to the flexibility of the whole system and the stiffness contribution of the non-structural elements. The findings also serve as the basis of the serviceability assessment of the pedestrian bridge.

2020 - Experiment on interaction of abutment, steel H-Pile and soil in integral abutment jointless bridges (IAJBs) under Low-cycle Pseudo-static displacement loads [Articolo su rivista]
Huang, F.; Shan, Y.; Chen, G.; Lin, Y.; Tabatabai, H.; Briseghella, B.
abstract

Soil-abutment or soil-pile interactions under cyclic static loads have been widely studied in integral abutment jointless bridges (IAJBs). However, the IAJB has the combinational interaction of soil-abutment and soil-pile, and the soil-abutment-pile interaction is lack of comprehensively study. Therefore, a reciprocating low-cycle pseudo-static test was carried out under an cyclic horizontal displacement load (DL) to gain insight into the mechanical behavior of the soil-abutment-pile system. Test results indicate that the earth pressure of backfill behind abutment has the ratcheting effect, which induced a large earth pressure. The soil-abutment-pile system has a favorable energy dissipation capacity and seismic behavior with relatively large equivalent viscous damping. The accumulative horizontal deformation in pile will be occurred by the effect of abutment and unbalance soil pressure of backfill. The test shows that the maximum horizontal deformation of pile occurs in the pile depth of 1.0b~3.0b of pile body rather than at the pile head due to the accumulative deformation of pile, which is significantly different from those of previous test results of soil-pile interaction. The time-history curve for abutment is relatively symmetrical and its accumulative deformation is small. However, the time-history curve of pile is asymmetrical and its accumulative deformation is dramatically large. The traditional theory of deformation applies only to the calculation of noncumulative deformation of pile, and the influence of accumulative deformation should be considered in practical engineering. A significant difference of inclinations in the positive and negative directions increases when the displacement load is relatively large. The rotation of abutment when bridge expands is larger than that when bridge contracts due to earth pressure of backfill.

2020 - Experimental Research on Effects of Debonding on Circular CFST Columns with Different Slenderness Ratios [Relazione in Atti di Convegno]
Briseghella, Bruno
abstract

Concrete filled steel tubular (CFST) structures have a wide range of applications in buildings and bridges due to the high bearing capacity. This beneficial composite action could be weakened even destroyed by debonding. In this paper, the debonding of circular CFST long columns subjected to axial load was investigated experimentally, taking the slenderness ratios and steel ratio as parameters. The simulation method of debonding by using soft PVC sheet was proposed, which can be pulled out after 7-days of concrete curing to avoid the inaccurate pull-out time which may lead to the failure of debonding simulation. The results of non-debonding and debonding CFST long columns were compared. The failure modes of the specimens show that the specimens under axial load are subjected to bending failure. The flexure curvatures of the non-debonding specimens are larger than the corresponding debonding specimens. Compared with the non-debonding specimens, the debonding specimens experience a strong concrete crushing during the loading process. The ultimate load-bearing capacity of debonding specimens is less than that of non-debonding specimens. With the increase of steel ratio or the decrease of slenderness ratio, the ultimate load-bearing capacity of the specimens increases. With the increase of steel ratio or slenderness ratio, the influence of debonding on the ultimate load-bearing capacity decreases. The lateral deflection of debonding specimens is less than that of non-debonding specimens. With the increase of steel ratio or slenderness ratio, the influence of debonding on the lateral deflection increases.

2020 - Experimental research on influence of debonding on circular CFST long columns subjected to eccentric load [Relazione in Atti di Convegno]
Xue, J. Q.; Liu, Z. H.; Zhang, Y. F.; Briseghella, B.; Chen, B. C.; Wei, J. G.
abstract

Debonding would seriously affect the beneficial confinement effect on core concrete from steel tube in Concrete Filled Steel Tubular (CFST) structures. The influences of debonding on the behaviour of CFST long columns subjected to eccentric compression were studied experimentally in this paper with the main parameters of steel ratio and slenderness ratio. It can be found that compared with the non-debonding CFST long columns subjected to eccentric load, the ultimate load-carrying capacity of debonding specimens are lower, the displacements corresponding to the ultimate load-carrying capacity and the lateral deflections at specimen mid-height are less. With an increase in steel ratio or slenderness ratio, the reduction coefficients on the ultimate load-carrying capacity of CFST long columns subjected to eccentric load increased. With a decrease in steel ratio or an increase in slenderness ratio, the reduction coefficients on the lateral deflection of CFST long columns subjected to eccentric load increased.

2020 - Finite element analysis of reinforced concrete bridge piers including a flexure-shear interaction model [Articolo su rivista]
Rasulo, A.; Pelle, A.; Lavorato, D.; Fiorentino, G.; Nuti, C.; Briseghella, B.
abstract

This paper discusses the seismic behavior of reinforced concrete (RC) bridge structures, focusing on the shear-flexure interaction phenomena. The assessment of reinforced concrete bridges under seismic action needs the ability to model the effective non-linear response in order to identify the relevant failure modes of the structure. Existing RC bridges have been conceived according to old engineering practices and codes, lacking the implementation of capacity design principles, and therefore can exhibit premature shear failures with a reduction of available strength and ductility. In particular, recent studies have shown that the shear strength can decrease with the increase of flexural damage after the development of plastic hinges and, in some cases, this can cause unexpected shear failures in the plastic branch with a consequent reduction of ductility. The aim of the research is to implement those phenomena in a finite-element analysis. The proposed model consists of a flexure fiber element coupled with a shear and a rotational slip spring. The model has been implemented in the OpenSEES framework and calibrated against experimental data, showing a good ability to capture the overall response.

2020 - Fujian Tulou Rammed Earth Structures: Optimizing Restoration Techniques Through Participatory Design and Collective Practices [Articolo su rivista]
Frangedaki, E.; Gao, X.; Lagaros, N. D.; Briseghella, B.; Marano, G. C.; Sargentis, G. F.; Meimaroglou, N.
abstract

Fujian Tulou is a significant part of the international built heritage. Renovation and strengthening of existing Haka Tulou's earth constructions can ensure a better quality of life for their residents, as well as contribute to a long-lasting prominence of China's heritage. Previous studies of Fujian Tulou mainly cover habitation patterns, construction features and architectural details. In this research a layout has been summarized of causes of deterioration, pathology of structure, focused on the buildings' conservation value and restoration, in terms of history, culture and construction technologies. Out of Fujian's more than 3,000 Tulou, only a few dozen have been awarded the status of World Heritage Sites by UNESCO. Along with that status, the 46 buildings chosen for the award. The buildings which belong to UNESCO's heritage are on list of possible restoration while the rest remain in disintegration and the villages are getting vacant through years. The answer for the restoration could be found through participation and team work of experts and habitants. A Tulou is usually inhabited by one family clan for several generations, and the enclosed structure allows to the members of the community to work together and participate in a common goal.Therefore, it is necessary to find new intervention techniques for these earthen buildings, or to adapt those already existing - and proved - to the specific characteristics of the material. This is the context in which the present research aims at contributing to the development of grouting and stitching the cracks by means of earthen mortar in rammed earth walls, as collective restoration techniques.

2020 - IMPAβ: Incremental modal pushover analysis for bridges [Articolo su rivista]
Bergami, Av; Nuti, C; Lavorato, D; Fiorentino, G; Briseghella, B
abstract

In the present study, the incremental modal pushover analysis (IMPAβ), a pushover-based approach already proposed and applied to buildings by the same authors, was revised and proposed for bridges (IMPAβ). Pushover analysis considers the effects of higher modes on the structural response. Bridges are structurally very different from multi-story buildings, where multimodal pushover (MPA) has been developed and is currently used. In bridges, consideration for higher modes is often necessary: The responses of some structural elements of the bridge (e.g., piers) influence the overall bridge response. Therefore, the failure of these elements can determine the failure of the whole structure, even if they give a small contribution total base shear. Incremental dynamic analysis (IDA) requires input accelerograms for high intensities, which are rare in the databases, while scaling of generated accelerograms with a simple increment of the scaling acceleration is not appropriate. This fact renders IDA, which is by its nature time-consuming, not straightforward. On the contrary, the change of input spectrum required by IMPA is simple. IMPAβ also utilizes a simple complementary method coupled to MPA, to obtain bounds at very high seismic intensities. Finally, the two incremental methods based on static nonlinear and dynamic nonlinear analyses are compared.

2020 - Influence of initial temperature method on temperature distributions on concrete box girder cross-sections [Relazione in Atti di Convegno]
Xue, J. Q.; Li, Z. X.; Lin, J. H.; Briseghella, B.; Huang, F. Y.; Chen, B. C.
abstract

The accuracy of initial temperature method is the key issue of the research on the temperature distributions on concrete box girder cross-sections. In order to analyze the influence of different initial temperature methods on the temperature distributions on concrete box girder cross-sections, a concrete box girder bridge was chosen as case study. Comparing with the measured data, it can be found that the method on using the same environmental conditions imposed cyclically for several days is necessary. Considering the difficulty of data collection, application scope and calculation accuracy, the initial temperature method assuming the air temperature at 0 am of the target date as the initial temperature, and the air temperature, wind speed and solar radiation of the target date imposed cyclically as the boundary conditions is proposed as the initial temperature method of the finite element model to carry out the research on the temperature distributions on girder cross-sections.

2020 - Lateral performance of midply wood shear walls with anchor tie-down system: Experimental investigation and numerical simulation [Articolo su rivista]
Guo, S.; He, M.; Li, Z.; Liang, F.; Chen, F.; Sun, Y.; Briseghella, B.; He, G.
abstract

This paper presents experimental and numerical studies on the lateral performance of midply wood shear walls. A kind of anchor tie-down system (ATS) is introduced into the wood shear wall, and two different wall-foundation connections (i.e., screwed connection and bolted connection) are considered. Reserved cyclic loading tests were conducted to investigate the failure modes, lateral load resisting capacity, stiffness degradation, and energy dissipation of four midply wood shear wall specimens. Test results show that with the installation of ATS, the lateral load resisting capacity, energy dissipation, and lateral stiffness of the specimen increased by 154%, 427%, and 93%, respectively. The pull-out failure of the wall studs was also avoided with the application of ATS. Compared with the midply wood shear wall specimens with bolted wall-foundation connection, the specimens with screwed wall-foundation connection dissipated more energy; however, the fatigue failure of the screws might lead to brittle failure of the shear wall. A nonlinear finite element model of the midply wood shear wall was then developed and verified with the test results. User-defined Q-pinch model was applied to simulate the sheathing-framing connection of the shear wall. The simulation results show that the hysteretic behavior of the specimen with ATS was well predicted. The experimental and numerical studies provide fundamental knowledge for the development and application of midply wood shear walls, especially for the application of such wall system into mid-rise timber structures.

2020 - Numerical analyses of joint with steel endplates, headed stud anchors and concrete cross-beam in continuous steel-concrete composite girder bridges [Relazione in Atti di Convegno]
Briseghella, Bruno
abstract

Short and medium span continuous steel-concrete composite (SCC) girder bridges are becoming more and more popular. The problems caused by the negative bending moment in the continuous SCC girders cannot be ignored. In order to investigate the performances of the continuous joints between adjacent SCC girders, consist of steel endplates and headed shear stud connected to concrete cross-beam, the finite element model was built by using ABAQUS software, of which the accuracy was verified by experimental results. The parametric analyses were carried out to investigate the influences of the strength and reinforcement ratio of the concrete slabs in SCC girders, and the diameters of the horizontal headed shear studs on the performances of the joints. The ultimate moment capacity of the joint increases with the increase in the strength and reinforcement ratio of concrete slab and the diameters of the horizontal headed shear studs.

2020 - Numerical analyses on flexural performance of UHPC link slababutment backwall system in jointless bridges [Relazione in Atti di Convegno]
Briseghella, Bruno
abstract

The link slab could be applied to the abutment-superstructure connections to eliminate deck joints to form a link slab-abutment backwall (LS-AB) system in jointless bridges. However, due to the rotation and longitudinal deformation of girder ends, the reinforced concrete LS-AB system may crack. In order to improve the crack resistance of the LS-AB system, the ultra-high performance concrete (UHPC) could be used. The finite element model was built by ABAQUS to investigate the flexural performance of the UHPC LS-AB system. The results indicated that UHPC could improve the ultimate load, bending stiffness and crack resistance of the LS-AB system. The cracks mainly appeared on the link slab under bending. With an increase in the ratio of rubber sheet length to span, the displacement corresponding to initial concrete cracks increase. The bending stiffness of the UHPC LS-AB system is mainly influenced by the material and rubber sheet length.

2020 - Numerical analyses on tension behaviors of ultra-high performance concrete link slab for jointless bridges [Relazione in Atti di Convegno]
Lin, J. H.; Briseghella, B.; Xue, J. Q.; Huang, F. Y.; Chen, B. C.; Nuti, C.
abstract

Link slab is proposed to eliminate deck joints for multi-span simply supported girder bridge. However, the conventional Reinforced Concrete (RC) link slab tends to produce cracks that cause leakage and deterioration. In order to improve the crack resistance of RC link slab, Ultra-High Performance Concrete (UHPC) link slab is proposed. Based on the test results of UHPC link slab under monotonic tensile loading, the validity and accuracy of the Finite Element Model (FEM) built by ABAQUS was verified. The parametric analyses based on the verified FEM were carried out to study the influence of different parameters on the tension behaviors of UHPC link slab. The results indicate that with an increase in rubber sheet length or reinforcement ratio, the maximum concrete stress at top fiber decreased by 13.8% and 17.9%, respectively. The tension stiffness is mainly influenced by the rubber sheet length and link slab thickness.

2020 - Numerical analysis of the mechanical behaviors of girders in jointless bridge considering the grade flat approach slab [Relazione in Atti di Convegno]
Tang, Y. F.; Briseghella, B.; Xue, J. Q.; Huang, F. Y.; Chen, B. C.; Nuti, C.
abstract

The approach slab of the jointless bridge can absorb and transmit the deformation of the girders due to temperature variations. However, the reactions from the approach slab can influence the mechanical behaviors of jointless bridges. The most common type of approach slab in jointless bridges is the Grade Flat Approach Slab (GFAS). The length of the approach slab, the sliding material and the subgrade material can affect the stresses of the approach slabs and the girders. The influence of the approach slabs was usually neglected. In this paper, one Deck-Extension Bridge (DEB) was chosen as the case study. The finite element models of the girders and the GFAS was built. Based on the force-displacement curve and friction coefficient obtain from the lab test, the horizontal and vertical springs were used to simulate the friction in the sliding materials and the supports under the GFAS. The results show that the simulation method of simplified spring is more constrained than the simulation method of shell element, the influence laws of the two connection structures of hinged and fixed are different. The influence of the parameters on the side span is greater than that of the mid span.

2020 - Optimal design criteria for form-finding of double-curved surfaces [Articolo su rivista]
Sulpizio, C.; Fiore, A.; Demartino, C.; Vanzi, I.; Briseghella, B.
abstract

The development of new digital design tools and fabrication technologies stimulated a large research interest in the design and construction of free-form architecture. Free-form architecture indicates the symbolic act of freeing architecture from the limitations of pure form. During the form-finding process, the priority is on identifying the geometry that enables the optimum force flow within the structure. This study focuses on the problem of the form-finding problem of concrete double-curved surfaces. First, a suitable form-finding optimization framework to optimize shell surfaces based on the surface Stress Density method is established. This framework is based on the use of different software such as Rhinoceros, Grasshopper, and Matlab. The stress density method is chosen because it allows obtaining an optimized shape starting by few parameters: the geometric characteristics of the model, the surface density factor and the magnitude of the load. In a second step, the study is focused on a single panel of the structure. Structural analyses of this panel are carried out using the commercial finite element software SAP2000 to demonstrate that it is a shape resistant structure. Finally, a new production process for concrete double-curved surfaces is presented showing a prototype at a small scale. This process is trying to satisfy the needs of new shapes within architectural design. The proposed solution is the improvement of an existing flexible mould formwork technology and represents the first attempt to reach a reusable, reconfigurable and affordable procedure.

2020 - Relevant outcomes from the history of Polcevera Viaduct in Genova, from design to nowadays failure [Articolo su rivista]
Nuti, C.; Briseghella, B.; Chen, A.; Lavorato, D.; Iori, T.; Vanzi, I.
abstract

Failures of structures are often tragic events, however represent an opportunity to improve the understanding of phenomena. In this paper, after the review of Bridge collapses, on August 14, 2018, the history of Polcevera Bridge is presented, starting from aging considerations done by its designer Riccardo Morandi in 1981, analyzing the outcomes of inspections in the years from mid ‘80s with references to Italian Regulations on inspections, the interventions done during bridge life, and finally some considerations on its collapse. The case is certainly a reference for reinforced concrete bridges built just after the 2nd world war in a highly corrosion-prone environment due to nearby sea and industrial as well as chloride pollution. Large reference is done to data included into the Report of the Commission of Italian Ministry of Infrastructures for the failure of Polcevera Bridge. Monitoring for assessment of performance decay due to corrosion is discussed with reference to the meaningful example considered.

2020 - Review of ultra-high performance concrete and its application in bridge engineering [Articolo su rivista]
Briseghella, Bruno
abstract

Due to the superior mechanical properties and durability, the ultra-high performance concrete (UHPC) has been widely used for the design of various types of structures, while research on its performance has been rapidly growing in the last five years. While the application of UHPC in bridge engineering is limited due to its higher cost, relatively little is known about the mechanical behavior of UHPC in different bridge components. In order to inform future research needs, this paper provides a comprehensive review of the properties of UHPC and its application in bridge engineering. Applications in various bridge components, such as the piers, girders, decks, and link slabs used for jointless bridges have been summarized. This review also discusses future research on optimized UHPC mix designs considering economic cost and its applications in both jointed and jointless bridges.

2020 - Seismic Assessment of Reinforced Concrete Frames: Influence of Shear-Flexure Interaction and Rebar Corrosion [Relazione in Atti di Convegno]
Briseghella, Bruno
abstract

The stock of existing buildings across most of the European earthquake-prone countries has been built before the enforcement of modern seismic design codes. In order to assure uniform levels of safety and reduce the social and economic impact of medium to high earthquakes costly seismic intervention plans have been proposed. But their application, in order to define which building should primarily be retrofitted, requires adequate vulnerability assessment methodologies, able to model the effective non-linear response and to identify the relevant failure modes of the structure. In the case of reinforced concrete (RC) buildings, due to the lack of application of capacity design principles and the aging effects due to exposition to an aggressive environment, existing structures can exhibit premature failures with a reduction of available strength and ductility. In the last couple of decades some state-of-the-art simplified models aiming at capturing the complex interaction between shear and flexural damage mechanisms as well as behavior of rebar corrosion have been proposed in specialized literature and, in some cases, implemented in regulatory building codes and guidelines. The present paper presents how those phenomena that have a significant impact in reducing the element capacity in term of strength and energy dissipation can be implemented in the assessment of the structures.

2020 - Shell-supported footbridges [Articolo su rivista]
Briseghella, Bruno
abstract

Architects and engineers have been always attracted by concrete shell structures due to their high efficiency and plastic shapes. In this paper the possibility to use concrete shells to support footbridges is explored. Starting from Musmeci's fundamental research andwork in shell bridge design, the use of numerical formfinding methods is analysed. The form-finding of a shellsupported footbridge shaped following Musmeci's work is first introduced. Coupling Musmeci's and Nervi's experiences, an easy construction method using a stay-inplace ferrocement formwork is proposed. Moreover, the advantage of inserting holes in the shell through topology optimization to remove less exploited concrete has been considered. Curved shell-supported footbridges have been also studied, and the possibility of supporting the deck with the shell top edge, that is along a single curve only, has been investigated. The form-finding of curved shell-supported footbridges has been performed using a Particle-Spring System and Thrust Network Analysis. Finally, the form-finding of curved shell-supported footbridges subjected to both vertical and horizontal forces (i.e. earthquake action) has been implemented.

2020 - Structural Optimization of a Steel Arch Bridge with Genetic Algorithm [Articolo su rivista]
Briseghella, Bruno
abstract

Structural optimization has become an important tool for structural designers. It helps the designers to find optimal design solutions with better exploitation of materials subject to various constraints. In this article, to face the critical issue of huge horizontal thrust occurred in the Calatrava bridge over the Grand Canal of Venice, single-objective and multi-objective genetic algorithm (GA) based optimization procedures are set up, and the thickness optimization of the bridge is carried out separately with the proposed design procedures and the optimization module implemented in ANSYS. The results are compared in terms of steel volume and horizontal thrust level. It shows that the GA-based design procedures are effective tools to achieve optimal design due to the global search ability of GA. Further, with these powerful tools, more reasonable thickness distributions of steel plates and tubes of the Calatrava bridge can be obtained, meanwhile, the horizontal thrust can be reduced remarkably, and hence the high cost due to the large horizontal thrust of original design could be reduced.

2020 - Temperature Monitoring and Response of Deck-Extension Side-by-Side Box Girder Bridges [Articolo su rivista]
Briseghella, Bruno
abstract

To enhance the durability of side-by-side box girder bridges, a common source of maintenance issues can be eliminated using the jointless bridge concept. Accurate estimation of the average effective bridge temperature range is a key issue. A deck-extension bridge containing side-by-side box girders was chosen as case study. The temperature distribution on the bridge cross section and the longitudinal thermal movement of the superstructure were monitored. Finite-element models of the bridge superstructure were developed, which indicated close agreement with measured temperature responses. The average effective temperature of girder cross sections could accurately predict the longitudinal thermal movement of the superstructure. The highest and lowest average effective bridge temperatures for side-by-side box girders were estimated for 12 cities in 4 climatic regions in China under historically extreme temperature conditions. For most cities, the difference between the highest and lowest average effective bridge temperatures exceeded the design temperature range. The Chinese-code design procedures may overestimate the allowable length of deck-extension bridges, because the code underpredicts the change in the average effective bridge temperature.

2020 - The collaboration between Fuzhou's and Roma Tre's Universities [Articolo su rivista]
Briseghella, Bruno
abstract

The collaboration that began with the University of Fuzhou in 2011, in the sector of the design of retrofitting of existing bridges, then extended to interventions on existing and historic buildings, with very innovative aspects compared to what has been developed in other universities and countries. This thanks to the peculiarities of the Italian and Chinese experiences in the construction and historical infrastructure sectors. We dealt with issues related to the adobe/rammed earth construction, new materials, innovative intervention and monitoring techniques. A broad and interdisciplinary collaboration has been created. The Sino Italian Center between the Universities of Roma Tre and Fuzhou, which was inaugurated in 2016 in Fuzhou, will now open an office in Roma Tre, represents a unique case for both Italy and Europe.

2020 - Vibration-based condition monitoring of a stress-ribbon pedestrian bridge [Relazione in Atti di Convegno]
He, L.; Zhang, Z.; Marano, G. C.; Briseghella, B.; Tavani, A.; Gregori, A.; Deng, C.
abstract

Operational modal analysis is performed on a stress-ribbon pedestrian bridge supported on butterfly arch. A highly-synchronous tri-axial wireless sensor network is deployed on the bridge deck to record the ambient vibration responses of the structure excited by wind and low-density walking pedestrians. Operational modal data are extracted by using stochastic subspace identification method. It’s found that the experimental mode shapes are characterized by symmetric and anti-symmetric vertical bending and several torsion modes. On the basis of the experimental results, an improved FE model that considers the abutment is built in order to simulate the structure as the self-balanced system. The new model is then updated with a sensitivity-based approach. The calibrated model can serve as the baseline model for long-term monitoring of the life-cycle performance of the bridge.

2020 - Wireless-based identification and model updating of a skewed highway bridge for structural health monitoring [Articolo su rivista]
He, L.; Reynders, E.; Garcia-Palacios, J. H.; Marano, G. C.; Briseghella, B.; De Roeck, G.
abstract

Vibration-based monitoring was performed on a short-span skewed highway bridge on the basis of wireless measurements. By means of operational modal analysis, highly accurate modal results (frequencies and mode shapes) were extracted by using a self-developed wireless acquisition system, for which the performance was verified in the field. In order to reproduce the experimental modal characteristics, a refined finite element model was manually tuned to reduce the idealization errors and then updated with the sensitivity method to reduce the parametric errors. It was found that to build a reliable Finite element (FE) model for application in structural health monitoring, the effects of superelevation and boundary conditions of a skewed bridge should be taken into account carefully.

2019 - A Heuristic Approach to Identify the Steel Grid Direction of R/C Slabs Using the Yield-Line Method for Analysis [Articolo su rivista]
Briseghella, Bruno
abstract

In the last few years, nonregular reinforced concrete (R/C) slabs have become more popular in buildings and bridges due to architectural or functional requirements. In these cases, an optimum design method to obtain the ultimate load capacity and the minimum reinforcement amount should be used. For simple R/C slabs, the yield-line method is extensively used in engineering practice. In addition to strength, the "true" failure mechanism is also obtained by identifying the parameters that define it and minimizing the collapse load. Unfortunately, when the mechanism is too complicated to be described or defined by several parameters (e.g., in slabs with complicated geometry), the method becomes more difficult because the system of nonlinear equations becomes harder to solve through traditional methods. In this case, an efficient and robust algorithm becomes necessary. In this paper, a structural analysis of R/C slabs is performed by using the yield-line method in association with a zero-th order optimization algorithm (the sequential simplex method) to avoid calculating gradients as well as any derivatives. The constraints that often limit these parameters are taken into account through the exterior penalty function method, leading to a successful solution of the problem. Considering that the direction of each yield-line is sought by minimizing the ultimate load and finding the parameters defining the collapse mechanism, another parameter concerned with the direction of an orthotropic reinforcement grid is introduced. In this way, the number of unknown parameters increases, but aside from obtaining the ultimate load and the parameters defining the collapse mechanism, the solution also finds both best and worst reinforcement orientations.

2019 - Curved footbridges supported by a shell obtained through thrust network analysis [Articolo su rivista]
Fenu, L.; Congiu, E.; Lavorato, D.; Briseghella, B.; Marano, G. C.
abstract

After Maillart's concrete curved arch bridges were built before the Second World War, in the second half of the past century and this century, many curved bridges have been built with both steel and concrete. Conversely, since the construction of Musmeci's shell supported bridge in Potenza, few shell bridges have been constructed. This paper explains how to design a curved footbridge supported by an anticlastic shell by shaping the shell via a thrust network analysis (TNA). By taking advantage of the peculiar properties of anticlastic membranes, the unconventional method of shaping a shell by a TNA is illustrated. The shell top edge that supports the deck has an assigned layout, which is provided by the road curved layout. The form of the bottom edge is obtained by the form-finding procedure as a thrust line, by applying the thrust network analysis (TNA) in a non-standard manner, shaping the shell by applying the boundary conditions and allowing relaxation. The influence of the boundary conditions on the bridge shape obtained as an envelope of thrust lines is investigated. A finite element analysis was performed. The results indicate that the obtained shell form is effective in transferring deck loads to foundations via compressive stresses and taking advantage of concrete mechanical properties.

2019 - Nonlinear static analysis by finite elements of a Fujian Hakka Tulou [Relazione in Atti di Convegno]
Briseghella, B.; Colasanti, V.; Fenu, L.; Nuti, C.; Spacone, E.; Varum, H.
abstract

Hakka Tulous are massive circular earth constructions of the Fujian Province, China, included in the UNESCO World Heritage list. They are subjected to earthquakes of medium magnitude, but their response to the seismic action is not yet investigated in depth. The seismic response of Fujian Tulous was herein investigated through pushover analysis modelling the Tulou structure by finite elements. Although the Tulou is a big construction with a circular earth wall of about fifty meters in diameter, a micromechanical approach was used to model the earth nonlinear behaviour. Even if no binder is added to the earthen material, the Concrete Damaged Plasticity model can be adopted and has shown to be effective in modelling its nonlinear behaviour, as well as the nonlinear response of the Tulou earth wall. Performing pushover analysis of a big earth structure using a micromechanical approach seems to give reliable results, that must be proved by future research.

2019 - On the form of the Musmeci's bridge over the Basento river [Articolo su rivista]
Briseghella, Bruno
abstract

The bridge over the Basento river in Potenza, Italy, designed by Sergio Musmeci, is supported by a continuous double-curvature RC shell optimized to reduce bending forces. This 300m long bridge can be considered as a unique representative example of pioneering research on the design and construction of optimized structures. First, the design process employed for determining the form of the shell and the relevant constructive issues are described. A refined 3D geometric model of the shell is then obtained through an aerial survey carried out by a commercial UAV and a photogrammetric image-based reconstruction. A recent formulation of the Force Density Method allowing for non-isotropic stress state is exploited to numerically derive the form of the supporting shell; it is validated versus the surveyed geometry of the shell by employing a nonlinear optimization procedure in order to identify forces and stresses to be used as input parameters. Finally, the derived form of the shell is tested by a Finite Element analysis to verify its funicular efficiency, i.e., whether it is capable to withstand design loads by pure membrane actions.

2019 - Optimum design of an arched truss under vertical and horizontal multi-load cases [Relazione in Atti di Convegno]
Fenu, L.; Marano, G. C.; Congiu, E.; Briseghella, B.
abstract

Simultaneous topology, shape (form-finding) and size optimization of steel arched trusses was performed under vertical multi-loading case and seismic action. To bear vertical multi-loading cases, optimum truss arches were optimized by shaping the two chords in order to suitably convert bending moments acting along the truss arch into axial forces in each arched chord, thus allowing to bear highly different multi-loading cases. The chord shape is identified by defining the form of the arched chords through Cubic Rational Bézier curves. Similarly, when considering the seismic action too, two arched chords are still considered, but lying on different planes. For this purpose, the upper chord of the truss arch has been supposed to lie on the horizontal plane, while the lower chord was shaped as an inclined arch. The two arches are connected by a bracing system, thus collaborating to bear the external loading. The horizontal arch primarily resists to the earthquake action that mainly determines its shape, while the vertical loads are transferred to the inclined arch, thus mainly affecting its shape.

2019 - Preliminary data and field observations of the 21st August 2017 Ischia earthquake [Articolo su rivista]
Briseghella, B.; Demartino, C.; Fiore, A.; Nuti, C.; Sulpizio, C.; Vanzi, I.; Lavorato, D.; Fiorentino, G.
abstract

On 21st August 2017, an earthquake (ML3.6; MW3.9; Md4.0) struck the municipality of Casamicciola Terme on the island of Ischia, Italy. It was a peculiar earthquake: low magnitude, very superficial (focus depth of about 1.7 km), centered in a high population density area. Despite the island was historically struck by destructive earthquakes during the last centuries, buildings vulnerability in the area was high. Many masonry buildings (main structural typology in Casamicciola Terme and on the island) collapsed or were severely damaged, occasionally exposing the original, dating back to end of nineteenth century, wooden frame that is one of the first examples of code designed anti-seismic structures in Italy. In this study, preliminary data and field observations of the 21st August 2017 Ischia earthquake are given. First, data from the permanent seismic network are used to assess seismic input characteristics and compare them to the known seismic hazard. Building vulnerability is then analyzed via the results of field observations carried out soon after the seismic event, thus providing significant information about quality of materials, construction techniques, structural performance and interpretation of possible damage mechanisms.

2019 - Probabilistic Seismic Response Analysis on Continuous Bridges Under Near-Fault Ground Motions [Articolo su rivista]
Ma, H. -B.; Zhuo, W. -D.; Lavorato, D.; Nuti, C.; Fiorentino, G.; Gu, Y.; Briseghella, B.
abstract

This paper focuses on the pulse-like near-fault ground motion, developing a probabilistic seismic demand model to estimate the seismic response of regular continuous bridges. A three-span bridge with continuous deck is taken as the basic case to establish 25 representative samples by changing the geometrical parameters and modeled with OpenSees software. The ground motions of both near fault and far fault are selected from PEER NGA strong ground motion database. The seismic response of the bridge is evaluated using the drift ratio at the top of the pier. A series of nonlinear dynamic time history analysis is carried out to compare the damage obtained with near-fault and far-fault ground motions for three different site conditions. Subsequently, a sensitivity analysis is performed on the design parameters according to the orthogonal experimental design methodology. After selecting the Housner intensity as the most suitable intensity measure and drift ratio as the engineering demand parameter, the probabilistic seismic demand model is established for the near-fault earthquake on the site II condition which is classified by Chinese design code. The results show that the near-fault earthquake can lead to more serious damage with respect to regular bridges and that the probabilistic seismic demand model allows for a quick evaluation of the seismic behavior of regular continuous bridges under pulse-like near-fault earthquake.

2019 - Probabilistic seismic demand model for regular bridges based on the modified Park-Ang damage index [Relazione in Atti di Convegno]
Briseghella, Bruno
abstract

In this paper, a modified damage model is established to solve the non-convergence problem existing in the Park-Ang damage index. The scatter of the modified damage index is significantly reduced compared to the original Park-Ang damage index. Then the finite element analysis models of 8 representative regular bridges samples were established with the main parameters variable such as the column height. The total 19120 increment dynamic analysis (IDA) curves were obtained by using the IDA method. These IDA curves are expressed in terms of one intensity measure (IM), i.e., the spectral acceleration at the fundamental period with 5% damping, and one engineering demand parameter (EDP), i.e., the modified Park-Ang damage index. At last, the probabilistic seismic demand model of regular bridges was established by using probability analysis based on the result of IDA curves. It is found that the seismic damage demand is reasonably standard beta distributed at given IM levels. The quadratic equation is suitable to establish the correlation between the mean value of the seismic damage demad and the IM. It is concluded that the established probabilistic seismic demand model is suitable for 3different site conditions and can largely simplify the computational effort of seismic demand in the performance-based seismic design and assessment of regular bridges.

2019 - Probabilistic seismic response and uncertainty analysis of continuous bridges under near-fault ground motions [Articolo su rivista]
Briseghella, Bruno
abstract

Performance-based seismic design can generate predictable structure damage result with given seismic hazard. However, there are multiple sources of uncertainties in the seismic design process that can affect desired performance predictability. This paper mainly focuses on the effects of near-fault pulse-like ground motions and the uncertainties in bridge modeling on the seismic demands of regular continuous highway bridges. By modeling a regular continuous bridge with OpenSees software, a series of nonlinear dynamic time-history analysis of the bridge at three different site conditions under near-fault pulse-like ground motions are carried out. The relationships between different Intensity Measure (IM) parameters and the Engineering Demand Parameter (EDP) are discussed. After selecting the peak ground acceleration as the most correlated IM parameter and the drift ratio of the bridge column as the EDP parameter, a probabilistic seismic demand model is developed for near-fault earthquake ground motions for 3 different site conditions. On this basis, the uncertainty analysis is conducted with the key sources of uncertainty during the finite element modeling. All the results are quantified by the “swing” base on the specific distribution range of each uncertainty parameter both in near-fault and far-fault cases. All the ground motions are selected from PEER database, while the bridge case study is a typical regular highway bridge designed in accordance with the Chinese Guidelines for Seismic Design of Highway Bridges. The results show that PGA is a proper IM parameter for setting up a linear probabilistic seismic demand model; damping ratio, pier diameter and concrete strength are the main uncertainty parameters during bridge modeling, which should be considered both in near-fault and far-fault ground motion cases.

2019 - Pseudo-static test on mechanic behavior of pile with pre-hole filled by foam in IABs [Relazione in Atti di Convegno]
Briseghella, Bruno
abstract

Comparing with the conventional jointed bridges, integral abutment bridges (IABs) have not the typical durability problems of expansion joints and bearings and could have better seismic performance due to the high redundancy and integrity. The concrete piles supporting the abutments are often considered as the most vulnerable component in IABs under longitudinal deformation of superstructure caused by temperature variation and seismic load. The pre‐hole method could be adopted to absorb the longitudinal deformation transferred from superstructure to the piles. Therefore, how to improve the energy dissipation of concrete piles to reduce the influence of seismic load is the key issue in IABs. In this paper, a technology based on piles with pre‐holes filled by damping material (called pre‐hole isolation pile) is proposed to improve the seismic response of IABs. The piles supporting the abutments of one real integral abutment bridge were chosen as case study. Pseudo‐static tests of two model piles with the scaled factor of 1/12.5 considering soil‐pile interaction (SPI) were performed. Foam was chosen as damping material. It could be found that compared with conventional piles, the hysteresis curve and the equivalent viscous damping ratio of pre‐hole isolation pile considering SPI was fuller and larger. According to the obtained results, the pre‐hole filled with foam technology could improve the energy dissipation of the concrete piles in integral abutment bridges and their seismic performance.

2019 - RC column repaired with hpfrcc and confined with cfrp: numerical analyses to evaluate the column section capacity [Capitolo/Saggio]
Briseghella, Bruno
abstract

This paper presents a numerical study to evaluate the behavior of reinforced concrete (RC) columns with circular section repaired and retrofitted by high-performance fiber-reinforced cement composites (HPFRCC) jackets and external carbon fiber-reinforced polymer (CFRP) wrapping. The column damage is due to degradation of concrete and steel rebars for effect of the corrosion. Different HPFRCC mix designs were considered to repair the column assuming different fiber types (polyethylene, stainless steel) and volume contents (1% or 2%). These HPFRCC concretes were developed and tested experimentally at the lab of the University of Roma Tre (Salvador Filho et al. in Mechanical properties of HPFRCC reinforced with different types and volumes of fibres [1]). The numerical analyses were conducted by means of fiber models using the software OpenSees (OpenSees structural software [computer software]. Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, [2]) applying a vertical load and a displacement history (section rotation). The analyzed sections represent the undamaged section, the section damaged for effect of rebar corrosion, and the repaired and retrofitted sections. The first numerical results about the section strength capacities for each type of repair material are discussed.

2019 - Research on Influence of Simulation Method of Inner Boundary Condition on Temperature Distributions on Cross-Sections of Concrete Box Girders [Articolo su rivista]
Xue, J. -Q.; Lin, J. -H.; Briseghella, B.; Huang, F. -Y.
abstract

In order to accurately simulate the temperature inside the box girders, we researched the temperature distributions on cross-sections of box girders by choosing appropriate simulation methods of inner boundary conditions. Taking a concrete box girder bridge as a study case, we measured the temperature distributions on the cross-sections of box girders on site. Moreover, we developed finite element models of the cross-sections of box girders by using MIDAS FEA software to analyze the influences of four simulation methods of inner boundary conditions (namely, measured temperature method, ambient temperature method, mean ambient temperature method and air element method) on the temperature distributions on the cross-sections of box girders, and analyzed the average temperatures of the cross-sections of box girders under historically extreme temperature conditions. The results indicate that the hourly temperature curves of the cross-sections of box girders calculated using the finite element model by the measured temperature method provide the closest agreement with measured hourly temperature curves. When there is a lack of measured temperature data from the inside of the box girders, the hourly temperature curves calculated using the finite element model by the air element method provide the closest agreement with measured hourly temperature curves. The influence of four simulation methods of inner boundary conditions on the average temperatures and positive vertical temperature gradients on the cross-sections of box girders is negligible. The air element method can be used to analyze the temperature distributions on the cross-sections of box girders under historically extreme temperature conditions. The air element method is proposed to carry out the research on the temperature distributions on cross-sections of concrete box girders.

2019 - Research on effective temperature of T‐shaped girder for jointless bridges in China [Relazione in Atti di Convegno]
Briseghella, Bruno
abstract

Jointless bridge has been proved to be a cost‐effective alternative to bridges with conventional joints. The longitudinal thermal movement of the superstructure is usually considered as the key parameter for designing jointless bridges. The average temperature of cross‐sections can be considered as the effective temperature of the superstructure. In order to accurately estimate the longitudinal thermal movement of the superstructure, the average temperature of cross‐sections should be obtained. The temperature distribution on cross‐sections of T‐shaped girders in one jointless bridge was monitored. A finite element model was implemented using the MIDAS‐FEA software, which is verified based on the monitoring results. Considering the historical extreme temperature conditions and the results of the parametric study, the peak values of the average temperature of T‐shaped girder cross‐sections for jointless bridges in different climate regions in China are recommended. Finally, the simplified formulae to predict the effective temperatures of T‐shaped girder cross‐sections for jointless bridges are proposed based on the correlation analysis.

2019 - Research on friction between grade flat approach slab and sliding material in jointless bridges [Relazione in Atti di Convegno]
Tang, Y.; Briseghella, B.; Xue, J.; Zhang, P.; Huang, F.; Chen, B.
abstract

The application of jointless bridges has been increasing year by year, because it could reduce the life‐cycle cost and improve the riding comfort. The approach slab in jointless bridges does not only have the function of road transition which is the same as the approach slab in bridges with expansion joints, but also transfer and absorb the deformation produced by the thermal expansion and contraction of the girder. The Grade Flat Approach Slab (GFAS) horizontally placed on the subgrade is one of the most common types of the approach slab in jointless bridges. The material placed between GFAS and subgrade should be able to properly slide to reduce the stress in GFAS. The friction coefficient between GFAS and sliding material is an important parameter affecting the mechanical behavior of GFAS in jointless bridges. In this paper, the tests of GFAS with different sliding materials subjected to horizontal displacement were conducted to obtain the corresponding friction coefficients (from 0.34 to 0.68). The mathematical model of bilinear spring could be adapted to simulate the friction function between GFAS and different sliding materials. One Deck‐Extension Bridge (DEB) that is one type of jointless bridges was chosen as a case study. The finite element model was implemented by using Midas‐Civil software. The influence of GFAS with different sliding materials on the mechanical properties of DEB under temperature variation was investigated. It can be concluded that the influence of the friction coefficient between GFAS and sliding material on the bending moment of DEB should be taken into account.

2019 - Seismic Analysis by Macroelements of Fujian Hakka Tulous, Chinese Circular Earth Constructions Listed in the UNESCO World Heritage List [Articolo su rivista]
Briseghella, B.; Colasanti, V.; Fenu, L.; Nuti, C.; Spacone, E.; Varum, H.
abstract

The overall seismic response of Hakka Tulous, massive traditional earth constructions located in the Fujian Province (China) and part of the UNESCO list of World Heritage buildings, is investigated. For this aim, non-linear static analysis (pushover) was used. Since Tulous are complex circular earth structures (about 50 m in diameter) stiffened by wooden frames along the whole inner perimeter of the circular earth wall, non-linear finite element models are hard to implement because convergence is difficult to achieve and very long computation time would be required given the large number of elements and degrees of freedom. For the above reasons, the equivalent frame approach is often used for masonry structures. Even if a few approximations are needed, non-linear static analysis of even very complex masonry structures can be successfully performed with fewer convergence problems and lower computational efforts. The seismic analysis of a representative circular Tulou is carried out. An extension to circular masonry structures of the analysis by macroelements through the equivalent frame method is hence studied. The results provides insight on the Tulou’s failure modes and on its overall seismic response. Since this is the first study on the overall seismic response of these complex earth constructions, further research is needed to deepen our knowledge of their structural behaviour.

2019 - Seismic duration effect on damping reduction factor using random vibration theory [Articolo su rivista]
Greco, R.; Vanzi, I.; Lavorato, D.; Briseghella, B.
abstract

Damping Reduction Factor plays a key role in scientific literature and Technical Codes, but till now existing formulations present differences and inconsistences probably because obtained by integration of real recorded events, thus sensible to specific used data. This paper investigates the relation between damping reduction factor and earthquake duration by means of random vibration theory. A stochastic process, that is non-stationary and filtered, is used to model a seismic event. The modulation function is suitably chosen to describe earthquakes characterized by different durations. The stochastic process peak theory allows to calculate damping reduction factor after the definition of the probabilistic response of a simple linear visco-elastic oscillator. The variability with seismic duration for different soil conditions and damping ratios is investigated. The study points out that damping reduction factor is more sensitive to seismic duration in the range of high period and on rigid soil with respect to other conditions. The results show that, if damping ratio or effective duration values are increased, the damping reduction factor value diminishes.

2019 - Seismic reassessment of the leaning tower of Pisa: Dynamic monitoring, site response, and SSI [Articolo su rivista]
Fiorentino, G.; Quaranta, G.; Mylonakis, G.; Lavorato, D.; Pagliaroli, A.; Carlucci, G.; Sabetta, F.; Monica, G. D.; Lanzo, G.; Aprile, V.; Marano, G. C.; Briseghella, B.; Monti, G.; Squeglia, N.; Bartelletti, R.; Nuti, C.
abstract

The Tower of Pisa survived several strong earthquakes undamaged over the last 650 years, despite its leaning and limited strength and ductility. No credible explanation for its remarkable seismic performance exists to date. A reassessment of this unique case history in light of new seismological, geological, structural, and geotechnical information is reported, aiming to address this question. The following topics are discussed: (1) dynamic structural identification based on recorded earthquake data; (2) geophysical site characterization using a two-dimensional array; (3) seismic hazard and site response analysis considering horizontal and vertical motions; and (4) soil-structure interaction (SSI) analysis calibrated using lab and field data. A substantial shift in natural period, from about 0.35 s to over 1 s (a threefold increase, the largest known for a building of that height) caused by SSI, a wave parameter (1∕σ) of about 0.3, and a minor effect of vertical ground motion are identified and may explain the lack of earthquake damage on the Tower. Recommendations for future research, including the need to establish a seismic bedrock deeper than 500 m, are provided.

2019 - Shaking table tests on an integral abutment bridge model: Preliminary results [Relazione in Atti di Convegno]
Briseghella, Bruno
abstract

Over the last decade, there was a renewed interest on Integral Abutment Bridges (IABs), characterized by the absence of bearing supports and expansion joints, leading to reduced construction and maintenance cost over ordinary bridges. Due to monolithic connections between abutments and deck, complex Soil-Structure Interaction (SSI) phenomena tend to develop between bridge and backfill in static and dynamic conditions, due to thermal expansion and earthquake action, respectively. An experimental campaign was conducted using the 3x3 m 6 DOF shaking table and the 5 m long shear stack of the University of Bristol, focusing on SSI effects between the IAB model and the backfill soil under earthquake loading. After a description of test set-up and of protocol, preliminary results will be illustrated and discussed.

2019 - Simplified method to design laterally loaded piles with optimum shape and length [Articolo su rivista]
Briseghella, Bruno
abstract

Optimum shape and length of laterally loaded piles can be obtained with different optimization techniques. In particular, the Fully Stress Design method (FSD) is an optimality condition that allows to obtain the optimum shape of the pile, while the optimum length can be obtained through a transversality condition at the pile lower end. Using this technique, the structure is analysed by finite elements and shaped through the FSD method by contemporarily checking that the transversality condition is satisfied. In this paper it is noted that laterally loaded piles with optimum shape and length have some peculiar characteristics, depending on the type of cross-section, that allow to design them with simple calculations without using finite element analysis. Some examples illustrating the proposed simplified design method of laterally loaded piles with optimum shape and length are introduced.

2019 - Steel truss-type arches optimization under multi-load cases [Relazione in Atti di Convegno]
Fenu, L.; Marano, G. C.; Congiu, E.; Briseghella, B.
abstract

Structural optimization of arches under multi-load cases is faced. For this aim, truss-type arches are to be considered because, under different load cases, bending effects unavoidably occur in single-rib arches shaped under one load case only. An effective procedure for simultaneous topology, shape and size optimization of truss-arches under multi-load cases is proposed. For this aim, shape, size and topology variables are assembled in a unique set of variables that are simultaneously optimised by the optimization algorithm. For given Pratt-type brace pattern, different topologies have been considered by varying the node number, whereas Cubic Rational Bézier curves have been used to shape the arch chords. Optimum diameter and thickness of the circular hollow section members was also obtained. Optimization was performed in MATLAB environment, by applying a modified Differential Evolution (DE) algorithm implemented with a Constraint Domination Selection (CDS) criterion. For each design variable vector, a FEM analysis of the resulting model has been carried out by SAP2000 to evaluate the objective function value (volume) feasibility of each design variable vector in terms of structural performance. Optimal solutions have been found and compared, providing useful suggestions to consider as guidelines in truss-arche design.

2019 - To compute or not to compute? [Articolo su rivista]
Briseghella, Bruno
abstract

In a previous paper “to retrofit or not to retrofit?” (Nuti and Vanzi, 2003) a straightforward procedure able to forecast the economic return of seismic structural upgrading was presented. More recently, the authors realized that the final mathematical results can be much simplified so as to allow back-of-an-envelope computation. The title of this paper tries to highlight precisely this aspect, namely that for many a regular seismic structural upgrading cases, nearly no computation is needed (apart from one subtraction and one multiplication) to assess their economic convenience. These findings are presented and discussed in this paper, together with a state of the art on the cost-studies available in literature and technical codes. The mathematical formulation leading to the proposed approximation is suitably explained, underlining its applicability field and comparing it with the rigorous solution. Also a table and a formula are furnished that alternatively allows to calculate the maximum estimation errors, in order to obtain an upper and lower bound for the maximum amount of money which should be allocated for seismic structural upgrading. Finally an application example is described, dealing with retrofitting of reinforced concrete viaducts, a widespread bridge typology in Italy. The adopted upgrading solution consists of a concrete jacket at the base of some piers, particularly suitable in order to increase their ductility.

2018 - Adaptive form-finding method for form-fixed spatial network structures [Articolo su rivista]
Briseghella, Bruno
abstract

An effective form-finding method for form-fixed spatial network structures is presented in this paper. The adaptive form-finding method is introduced along with the example of designing an ellipsoidal network dome with bar length variations being as small as possible. A typical spherical geodesic network is selected as an initial state, having bar lengths in a limit group number. Next, this network is transformed into the ellipsoidal shape as desired by applying compressions on bars according to the bar length variations caused by transformation. Afterwards, the dynamic relaxation method is employed to explicitly integrate the node positions by applying residual forces. During the form-finding process, the boundary condition of constraining nodes on the ellipsoid surface is innovatively considered as reactions on the normal direction of the surface at node positions, which are balanced with the components of the nodal forces in a reverse direction induced by compressions on bars. The node positions are also corrected according to the fixed-form condition in each explicit iteration step. In the serial results of time history, the optimal solution is found from a time history of states by properly choosing convergence criteria, and the presented form-finding procedure is proved to be applicable for form-fixed problems.

2018 - Asynchronous earthquake strong motion and RC bridges response [Articolo su rivista]
Briseghella, Bruno
abstract

The dynamic response of long structures (e.g., bridges) is sensitive to the spatial variability of strong ground motion (asynchronous motion). Ground motion differences increase from point to point with increasing foundation distance. This latter is due to two physical phenomena: soil-wave interaction, that causes the loss of coherence and local amplification; wave traveling with finite velocity, that causes signals time lag. This ground motion variability produces a different structural demand compared to the synchronous one, which is the only one considered by designers in the majority of cases. A few codes consider this type of actions, therefore further research efforts are necessary. In this study, asynchronous ground motions are generated by means of a new generation procedure implemented in the software GAS 2.0 using as input the simultaneous strong motion records from the April 6th, 2009, L'Aquila (Italy) at the seismic stations AQA and AQV, located in the Aterno River valley. These records are used to calibrate the generation model and to produce sets of asynchronous earthquake sampling. The asynchronous earthquake sets are applied on a typical highway reinforced concrete bridge to study its dynamic response considering two different configurations: non-isolated with traditional supports and isolated bridge with lead rubber bearings. The bridge is placed in two positions along the wave propagation direction: a position near one recording station and a position between the two stations to consider local soil effects. The response parameters investigated are the maximum relative displacements of soil and deck. The results show that there is an important variation of relative displacement along the direction of wave propagation due to asynchronous motion with effects that designer should consider for the structural details design of isolated and non-isolated bridges.

2018 - Design and field tests of a deck-extension bridge with small box girder [Articolo su rivista]
Briseghella, Bruno
abstract

A jointless bridge could fundamentally eliminate vulnerable deck joints, thereby meeting the need for sustainable development of bridges, especially for an expressway with high-speed traffic. In this paper, one jointless bridge (deck-extension bridge) with a small box girder in an expressway was chosen as a case study to examine the structural design, construction and field test. The field tests of the bridge indicated that the designed and constructed structures can satisfy the requirement for service performance of the deck-extension bridge. Some key technologies, such as the position of longitudinal reinforcements in the superstructure-approach slab connections and the arrangement of the sliding material layers, were introduced. The longitudinal thermal movement of the superstructure in the deck-extension bridge with a small box girder could be predicted accurately by using the average temperature of the cross section of a small box girder. The finite element model, built by using the MIDAS program, was used to analyze the temperature distribution on the cross section of a small box girder, the accuracy of which could be verified by comparing with the measured values. The maximum longitudinal thermal movement of the superstructure in deck-extension bridges with a small box girder under historically extreme temperature conditions was predicted.

2018 - Experimental and numerical investigation of the static performance of innovative prefabricated high-strength composite columns [Articolo su rivista]
Briseghella, Bruno
abstract

An innovative high-performance precast beam-to-column joint for multi-storey framed structures is introduced. The proposed solution consists of coupling between Composite Steel Truss Concrete (CSTC) beams with a concrete base and High-Strength Concrete (HSC) columns. This paper focuses mainly on the static performance of prefabricated HSC columns, including experimental and numerical investigations. The finite element model of the structural system is calibrated on experimental static testing evidence. On the basis of the data collected, the finite element model is used to evaluate the strength domain of members and optimize the related coupling system between columns. Aiming to limit time-consuming analyses and provide practical rules for design, an analytical simplified procedure is introduced to compute the assembly's strength domain. An analytical approach is adopted to estimate the reference design strength for the considered composite columns, accounting for the partial safety factor imposed by codes and allowing for estimation of the limit on the number of storeys for frames adopting the proposed precast technology.

2018 - Experimental study on joint resistance and failure modes of concrete filled steel tubular (CFST) truss girders [Articolo su rivista]
Huang, W.; Fenu, L.; Chen, B.; Briseghella, B.
abstract

Concrete Filled Steel Tubular (CFST) structures are increasingly used not only for columns in tall buildings but also in the arch trusses of many arch bridges and in the truss girders of buildings and bridge decks. Therefore, the chords of Circular Hollow Section (CHS) truss arches and girders are increasingly filled with concrete, effectively making them CFST structures. In addition to the strength and stiffness of the CFST members, the failure mode of the CFST joint connecting them to the tubular member is also affected by the concrete filling. In this study, truss girders with different web arrangements were tested, and their behaviour investigated. The girders were not slender because they were designed to attain the peak limiting state for joint failure rather than chord failure due to bending moments. Moreover, two other types of girders were tested: one without concrete-filled chords (CHS girder) and another with only the upper chord filled with concrete; thus allowing an investigation of how a concrete-filled chord affects joint failure mode. The geometry of the CHS girder joints was such that only chord face failure and punching shear failure could occur. The former required an inward deformation that was prevented by the concrete filling in a CFST girder with similar geometry. Finally, the study considers extending the Eurocode 3 and the AWS D1.1 code formulae, originally proposed for CHS joints, to calculate the resistance of CFST joints.

2018 - Influence of soil type on damping reduction factor: A stochastic analysis based on peak theory [Articolo su rivista]
Briseghella, Bruno
abstract

Damping reduction factor plays a central role both in scientific literature and seismic codes, but still now proposed formulations show a quite large scatter. The main goal of the present work is to explore a new definition of the damping reduction factor. The concept of stochastic response spectrum is adopted in order to predict the earthquake response of a linear SDoF system, on the basis of the random vibration theory for non-stationary process. The peak of the response of a SDoF system under a non-stationary stochastic process is used to define the stochastic displacement spectrum. The damping reduction factor is thus evaluated as the ratio between the maximum displacement of systems with a given damping and a conventional one subject to the same earthquake.

2018 - Longitudinal Joint Performance of a Concrete Hollow Core Slab Bridge [Articolo su rivista]
Barbieri, D. M.; Chen, Y.; Mazzarolo, E.; Briseghella, B.; Tarantino, A. M.
abstract

Hollow core slab bridges are constructed by placing prefabricated or prestressed box beams adjacent to each other, grouting the small longitudinal space (hinge-joint) between the slabs and casting a reinforced concrete deck. The longitudinal cracking appearing at hinge-joint locations leads to a premature deterioration of the deck. This paper presents a theoretical and experimental study of a hollow core slab bridge composed of three beams and a cast-in-place deck. A real-size specimen was built according to Chinese code specifications. The behavior of the longitudinal joints was investigated by applying the standard vehicle load. The tests do not highlight any longitudinal cracks. A finite element model was created from the experimental data. A finite element parametric analysis revealed some practical design indications regarding the following inputs: deck thickness, concrete strength, and hinge-joint steel bars. Furthermore, these analyses testify that C-shape and X-shape stirrups do not play an active role in preventing the joint longitudinal cracks. This research confirms the reliability of the design method, at least for static loads, while further studies are needed to investigate the effect of both periodical loadings and different temperatures on upper and lower surfaces of the beams.

2018 - Optimal arches shape for single-point-supported deck bridges [Articolo su rivista]
Briseghella, Bruno
abstract

The arch shape is a timeless structural solution as it has been widely used in the past but is still a common solution adopted nowadays for large spans. Structural efficiency depends primarily on optimal material exploitation, which allows us to minimize the structural volume. The paper is framed in the context of optimization of arch structures, and analytical design criteria are proposed, dealing with a specific class of deck bridges supported in the mid-span by arches. The investigation deals with a simplified structural scheme, constituted by statically determinate plane arches under self-weight and a single vertical load in the key section, exerted by the deck supports. The optimization criterion assumes a constant normal stress in all arch sections and the resulting arch shape is computed in closed form. Finally, the existence condition for the proposed solution is provided and some numerical examples are introduced.

2018 - Optimum shape and length of laterally loaded piles [Articolo su rivista]
Briseghella, Bruno
abstract

This study deals with optimum geometry design of laterally loaded piles in a Winkler's medium through the Fully Stressed Design (FSD) method. A numerical algorithm distributing the mass by means of the FSD method and updating the moment by finite elements is implemented. The FSD method is implemented here using a simple procedure to optimise the beam length using an approach based on the calculus of variations. For this aim two conditions are imposed, one transversality condition at the bottom end, and a one sided constraint for moment and mass distribution in the lower part of the beam. With this approach we derive a simple condition to optimise the beam length. Some examples referred to different fields are reported. In particular, the case of laterally loaded piles in Geotechnics is faced.

2018 - Parameter identification of degrading and pinched hysteretic systems using a modified Bouc–Wen model [Articolo su rivista]
Pelliciari, M.; Marano, G. C.; Cuoghi, T.; Briseghella, B.; Lavorato, D.; Tarantino, A. M.
abstract

The Bouc–Wen (BW) model is a successful differential equations model used to describe a wide range of nonlinear hysteretic systems. However, it is unable to describe force degradation, stiffness degradation and pinching effects. Therefore, Baber and Noori proposed a generalisation, developing the Bouc–Wen– Baber–Noori (BWBN) model. Nevertheless, it is composed of many parameters and complex pinching and degrading functions. Thus, it is necessary to develop a simpler and reliable model to be used for practical applications. In this paper, a modified BW model is proposed. It involves a more direct physical meaning of each parameter and allows achieving a substantial reduction of computational effort and numerical deficiencies. This is obtained through simpler pinching and degrading functions that entail a decrease of the number of parameters. The result is a straightforward model, capable of predicting the behaviour of degrading and pinched hysteretic systems. An application of the proposed scheme to a real case is also presented, in which reinforced concrete bridge piers that were physically tested in the laboratory are considered. The force–displacement data are used to perform the identification process of the model parameters via a Genetic Algorithm. The numerical results are accurate since they coincide with the experimental ones.

2018 - Seismic behavior of a low-rise horizontal cylindrical tank [Articolo su rivista]
Fiore, A.; Rago, C.; Vanzi, I.; Greco, R.; Briseghella, B.
abstract

Cylindrical storage tanks are widely used for various types of liquids, including hazardous contents, thus requiring suitable and careful design for seismic actions. The study herein presented deals with the dynamic analysis of a ground-based horizontal cylindrical tank containing butane and with its safety verification. The analyses are based on a detailed finite element (FE) model; a simplified one-degree-of-freedom idealization is also set up and used for verification of the FE results. Particular attention is paid to sloshing and asynchronous seismic input effects. Sloshing effects are investigated according to the current literature state of the art. An efficient methodology based on an “impulsive-convective” decomposition of the container-fluid motion is adopted for the calculation of the seismic force. The effects of asynchronous ground motion are studied by suitable pseudo-static analyses. Comparison between seismic action effects, obtained with and without consideration of sloshing and asynchronous seismic input, shows a rather important influence of these conditions on the final results.

2018 - Severely damaged reinforced concrete circular columns repaired by turned steel rebar and high-performance concrete jacketing with steel or polymer fibers [Articolo su rivista]
Xue, J.; Lavorato, D.; Bergam, A. V.; Nuti, C.; Briseghella, B.; Marano, G. C.; Ji, T.; Vanzi, I.; Tarantino, A. M.; Santini., S.
abstract

2018 - Solar radiation parameters for assessing temperature distributions on bridge cross-sections [Articolo su rivista]
Briseghella, Bruno
abstract

Solar radiation is one of the most important factors influencing the temperature distribution on bridge girder cross-sections. The bridge temperature distribution can be estimated using estimation models that incorporate solar radiation data; however, such data could be cost- or time-prohibitive to obtain. A review of literature was carried out on estimation models for solar radiation parameters, including the global solar radiation, beam solar radiation and diffuse solar radiation. Solar radiation data from eight cities in Fujian Province in southeastern China were obtained on site. Solar radiation models applicable to Fujian, China were proposed and verified using the measured data. The linear Ångström–Page model (based on sunshine duration) can be used to estimate the daily global solar radiation. The Collares-Pereira and Rabl model and the Hottel model can be used to estimate the hourly global solar radiation and the beam solar radiation, respectively. Three bridges were chosen as case study, for which the temperature distribution on girder cross-sections were monitored on site. Finite element models (FEM) of cross-sections of bridge girders were implemented using the Midas program. The temperature–time curves obtained from FEM showed very close agreement with the measured values for summertime. Ignoring the solar radiation effect would result in lower and delayed temperature peaks. However, the influence of solar radiation on the temperature distribution in winter is negligible.

2018 - Use of Plastic Correction Formula to Improve Accuracy of Welding Residual Stress Test with Blind-Hole Method [Articolo su rivista]
Briseghella, Bruno
abstract

The blind-hole method is the most widely used approach to experimentally determine the distribution of residual stress. This paper aims to improve test accuracy of welding residual stress and conducts an experimental study on the strain release factors involved when using the blind-hole method for Q235 and Q345, two steels commonly used in building structures. The ranges of strain release factors A and B in the elastic stage, the effects of strain release factors on residual stress calculated values, and the plastic corrected strain release factors are analyzed considering of the effect of plastic deformation around the blind hole on measurement accuracy. Finally, a simplified calculation formula to determine strain release factors is proposed for use with the blind-hole method. Results show that in the elastic stage, strain release factor A for Q235 and Q345 ranges from −0.399 to −0.525 and strain release factor B from −0.791 to −0.960. Changing the strain release factors A and B shows that calculated residual tensile stress varies in relation to a decrease in both factor values. However, there is a increase in calculated residual compressive stress with a decrease in the strain release factor A value, but there is an decrease with a decrease in strain release factor B value. Calculated residual stress applied to elastic strain release factors is compared with that applied to amended plastic strain release factors for Q235 steel. The maximum deviation between calculated residual stress and test stress is reduced from 21.1 to 1.0%, and for Q345 steel from 26.5 to 1.2%. It is thus evident that the plastic correction formula proposed in this paper can be used in calculations when conducting a residual stress test.

2018 - Volume/thrust optimal shape criteria for arches under static vertical loads [Articolo su rivista]
Briseghella, Bruno
abstract

Arches are widely used when large spans are necessary, e.g. to overpass large rivers, and further possess unquestioned aesthetics advantages. Their structural efficiency depends primarily on optimal material exploitation, i.e. minimization of internal stress eccentricity, and on minimization of structural material volume. An efficient structure, under these terms, further requires simpler and lighter scaffolding, contributing in minimizing construction costs. Although arches have millenary use and many researches dealing with this typology are available in literature, there is still scope for design optimization. The proposed study is framed within this context. Investigation is limited to statically determinate plane arches under vertical load. The problem of finding the profile of an equal strength catenary subjected to its self-weight is spread out to the case of an inverted catenary of equal strength under its self-weight and an external constant load. In the first optimization step, constant normal stress is imposed at all sections, to maximize material exploitation, and the resulting arch centerline shape is computed in closed form. In the second step, the ensemble of foundations and arch is considered and optimized, taking the linear combination of arch weight and thrust as objective function. The linear combination is dependent on a single variable, and minima of the objective function (i.e. optimal geometric shape parameters) are computed and charted to be simply used in the design process.

2017 - Degrading bouc-wen model parameters identification under cyclic load [Articolo su rivista]
Marano, G. C.; Pelliciari, M.; Cuoghi, T.; Briseghella, B.; Lavorato, D.; Tarantino, A. M.
abstract

The purpose of this article is to describe the Bouc-Wen model of hysteresis for structural engineering which is used to describe a wide range of nonlinear hysteretic systems, as a consequence of its capability to produce a variety of hysteretic patterns. This article focuses on the application of the Bouc-Wen model to predict the hysteretic behaviour of reinforced concrete bridge piers. The purpose is to identify the optimal values of the parameters so that the output of the model matches as well as possible the experimental data. Two repaired, retrofitted and reinforced concrete bridge pier specimens (in a 1:6 scale of a real bridge pier) are tested in a laboratory and used for experiments in this article. An identification of Bouc-Wen model's parameters is performed using the force-displacement experimental data obtained after cyclic loading tests on these two specimens. The original model involves many parameters and complex pinching and degrading functions. This makes the identification solution unmanageable and with numerical problems. Furthermore, from a computational point of view, the identification takes too much time. The novelty of this work is the proposal of a simplification of the model allowed by simpler pinching and degrading functions and the reduction of the number of parameters. The latter innovation is effective in reducing computational efforts and is performed after a deep study of the mechanical effects of each parameter on the pier response. This simplified model is implemented in a MATLAB code and the numerical results are well fit to the experimental results and are reliable in terms of manageability, stability, and computational time.

2017 - Equivalent damping of bilinear hysteretic SDOF system considering the influence of initial elastic damping [Articolo su rivista]
Liu, T; Briseghella, B; Zhang, Ql; Zordan, T
abstract

The premise of equivalent linearization method is that the peak response of an inelastic system can be estimated as the peak response of a linear elastic system having reduced stiffness and increased damping. Different approaches have been used to determine the properties of the equivalent linear system, in particular the equivalent damping ratio. In general, equivalent damping is specified as the sum of elastic and hysteretic component, where the former is assumed to be constant, and the latter depends on the ductility and hysteresis model. It is found that, however, many studies only focus on the definition of hysteretic damping and omit the influence of elastic damping on the prediction accuracy of equivalent linearization method. Motivated by this limitation, comprehensive parametric analysis is performed in this paper based on bilinear hysteretic SDOF systems to identify the influence of elastic damping. Results show that elastic damping has significant influence on the estimation accuracy of equivalent linearization method. To improve the estimation accuracy of equivalent linearization method, improved method of equivalent damping is proposed by considering the influence of elastic damping. It is found that the proposed method is able to provide accurate and conservative values of equivalent damping for practical design of base isolation systems.

2017 - Experimental and numerical investigation of the cyclic behaviour of an innovative prefabricated beam-to-column joint [Articolo su rivista]
Huang, Y.; Briseghella, B.; Mazzarolo, E.; Zordan, T.; Chen, A.
abstract

2017 - Retrofitting of simply supported bridges using integral abutment bridge concept [Relazione in Atti di Convegno]
Xue, J.; Briseghella, B.; Chen, B.; Zordan, T.; Siviero, E.; Oddone, S.; Mattia, F.
abstract

The research on the retrofitting method using the concept of integral abutment bridge to solve the durability problems of simply supported bridges was carried out. The general retrofitting process adopted by real projects and the mechanical properties increment after retrofitting were summarized. A simply supported bridge in Italy was analyzed numerically using finite element model built by SAP2000 with inclusion of soil-structure interaction. The influence of old and new Italian codes on the mechanical properties of different static schemes, including simply supported, semi-integral and fully integral, was investigated.

2017 - Seismic behaviour of isolated RC bridges subjected to asynchronous seismic input [Relazione in Atti di Convegno]
Briseghella, Bruno
abstract

The seismic actions used to design long structures, as bridges, should be attentively evaluated, since, due to seismic wave propagation through soil, at distant foundation points signals are different. Signal frequency content varies from point to point for at least two reasons: soil-wave interaction; wave traveling time from one point to the other. Asynchronous seismic waves produce distortions at the bridge foundations which are usually not considered in design practice. In this paper, the responses of two RC bridges, one with deck supported by traditional bearing and one by Lead Rubber Bearings (isolators), subjected to asynchronous or synchronous signals were studied. These signals were generated at the surface starting from the EW components of the main shock recorded at two recording stations (AQA, AQV) near L'Aquila city (Italy) on 4-06-2009. The soil distortions which produce maximum stresses on deck or on piers were evaluated for the two bridges (non-isolated and isolated) in case of synchronous and non-synchronous excitations. The first results are discussed to understand the effects of asynchronous excitation on the responses of the two bridges.

2017 - Soil Structure Interaction under Semi Static Loads in an Integral Abutment Bridge [Relazione in Atti di Convegno]
Briseghella, Bruno
abstract

To solve the durability problem of expansion joints and bearings, integral abutment bridges (IABs) have become increasingly popular. Soil Structure Interaction (SSI) is a fundamental aspect for reaching a thorough understanding of this type of structure not only for newly built bridges but also in the retrofitting of existing ones. Under imposed actions, e.g., horizontal expansion and contraction induced by thermal variation and time-dependent effects (creep and shrinkage), the connection between a super- and substructure responding as a frame structure makes IABs different from other conventional bridges that introduce forces due to SSI. Therefore, the overall horizontal stiffness is mainly due to i) the piles' stiffness, which is usually flexible enough to allow for the deformation of the superstructure and strong enough to carry out the vertical loads, and ii) the type of soil behind the bridge abutment, which has a different stiffness depending on its compaction and composition. Several approaches have been proposed in the literature to consider these types of interaction. In this paper, the accuracy of different formulations commonly used in IABs' design and based on p-y curves was evaluated. Formulations for piles and abutments were first introduced. Then, a fully integral abutment bridge built in China was considered as a case study. A finite element model of the bridge using SAP2000 software was implemented, and the influence of different methods and formulations was investigated. Finally, the obtained results for different types of soil and approaches were compared and discussed.

2017 - Surface generation of asynchronous seismic signals for the seismic response analysis of bridges [Relazione in Atti di Convegno]
Briseghella, Bruno
abstract

The seismic signals, recorded at different surface points during the propagation of the seismic waves through soil, show differences due to the soil-wave interaction. The seismic design actions should be evaluated properly in case of distant foundation points as these differences can be great. In this paper, asynchronous seismic signals are generated at surface starting from a few well-known recordings for the same seismic event. The EW accelerometric components of the main shock recorded at two recording stations (AQA, AQV) near L'Aquila city (Italy) on 4-06-2009 are the generation inputs. The seismic wave propagates along the direction between AQA and AQV. These signals are representative of a possible asynchronous excitation applied on a bridge. Five arrays of asynchronous accelerograms are generated at the foundations of the bridge to perform statistical elaboration of the results. Different bridge positions are supposed along the propagation direction of the wave to evaluate the spatial variability of the generated signals. The generated signals at AQA and AQV stations are compared with the available recordings at the same points (generation inputs) in term of power spectra, acceleration and displacement response spectra. Finally, the most detrimental soil distortions for the bridge deck are calculated for some bridge positions.

2017 - The optimal shapes of piles in integral abutment bridges [Articolo su rivista]
Chenglana, ; Briseghella, Bruno; Fenu, Luigi; Xueb, Junqing; Zordana, Tobia
abstract

Integral abutment bridges (IABs) can be used to avoid the durability issues associated with bearings and expansion joints. For this type of bridge, the design of the optimal pile foundation, especially with respect to the horizontal stiffness, is a challenging issue. A structural optimization approach is proposed in this paper to optimize the pile foundation shape in integral abutment bridges. A procedure was implemented based on linking MATLAB, where an optimization code was developed, and OpenSees, which was used as the finite element solver. The optimization technique was compared with other techniques developed in previous researches to verify its reliability; the technique was then applied to a real 400 m-long IAB building in Verona, Italy, as a case study. The following two possibilities were considered and compared: (a) a pile with two different diameters along the depth and (b) a pile with a pre-hole. In fact, to increase the lateral and rotational flexibilities of the pile head, piles for an integral abutment bridge foundation are often driven into pre-deep holes filled with loose sand. Finally, the case of super-long integral abutment bridges (L = 500 m) with a corresponding displacement on one bridge end of approximately 50 mm was analysed. The following four pile design optimization cases were considered with similar study criteria as the Isola della Scala Bridge: (a) a pinned pile head for semi-integral abutment, (b) a fixed pile head without a pre-hole, (c) a fixed pile head with a pre-hole of any depth, (d) a fixed pile head of a pre-hole with a depth limit (< 2 m) allowing for enough embedded length for the friction pile. The case studies confirmed the potential of the proposed optimization techniques for finding the optimal shape of piles in integral abutment bridges.

2017 - Ultra-high-performance fibre-reinforced concrete jacket for the repair and the seismic retrofitting of Italian and Chinese RC bridges [Relazione in Atti di Convegno]
Lavorato, D.; Bergami, A. V.; Nuti, C.; Briseghella, B.; Xue, J.; Tarantino, A. M.; Marano, G. C.; Santini, S.
abstract

The seismic behavior of Chinese RC (Reinforced Concrete) bridge piers with insufficient seismic details, severely damaged after an earthquake and then repaired and retrofitted by rapid interventions is investigated. The proposed interventions are applied on the damaged steel rebar and concrete parts in plastic hinge zone to guarantee the proper plastic dissipation of the seismic energy and the necessary shear strength and ductility improvements. New longitudinal shaped rebars and concrete jackets are used to substitute the pier damaged parts. Two repair and retrofitting procedures are presented and applied on 1:6 scaled pier specimens designed on the base of Chinese codes [1]-[3]: the first one uses an self-compacting concrete to build the concrete jacket and carbon Fiber Reinforced Polymer (CFRP) wrapping to assure the seismic improvements; the second one uses an ultra-high performance fiber reinforced concrete (UHPFRC) with steel fiber to build the concrete jacket and to assure the seismic upgrading allowing time and cost saving. The results of the first experimental tests on 1:6 scaled pier specimens repaired and retrofitting by the two procedures, are compared and discussed.

2016 - A RAPID REPAIR AND RETROFITTING INTERVENTION FOR SEISMIC DAMAGED CHINESE BRIDGE USING FIBER REINFORCED CONCRETE SHAPED REBAR AND EXTERNAL CFRP OR STEEL WRAPPING [Relazione in Atti di Convegno]
Lavorato, D.; Bergami, A. V.; Nuti, C.; Briseghella, B.; Tarantino, A. M.; Santini, S.
abstract

A rapid repair and retrofitting technique applied on reinforced concrete (rc) bridges damaged after a strong earthquake, can be a very effective solution to guarantee the use of the bridge for the emergency response in short time. This repair intervention makes possible a proper plastic dissipation distribution on the rebars in plastic hinge only and increases the original insufficient shear strength minimizing the intervention time and cost. In this paper, the technique was applied on the most damaged pier of an irregular rc bridge designed according to Chinese codes (JTG D60-2004, JTG D62-2004 and JTG/T B02-012008) but with insufficient transversal steel reinforcement. The rc pier repair operations consist in: substitution of the original damaged rebar parts by shaped rebar; restoration of the damaged concrete parts by concrete with fibers in plastic hinge only. In particular, this research focuses on the use of fiber concrete to increase the insufficient original shear strength and ductility of the pier. Compression and flexural tests on fiber concrete specimens were performed to determine the variation of the concrete mechanical properties with different fiber contents. Furthermore, the shear strength of the repaired pier specimen was evaluated by CNR-DT 204/2006 formulations considering the contribution of the new and of the original concrete parts. Finally, some pier specimens (scale 1: 6) were repaired using different concrete mixture with different fiber contents to prove the feasibility of the intervention in situ.

2016 - A probabilistic evaluation of an integral abutment bridge [Relazione in Atti di Convegno]
Munoz, M.; Briseghella, B.; Xue, J.; Smaldini, P.; Nuti, C.
abstract

In last years, a new trend in the construction of short and medium span bridges has raised in some countries. The solution of an Integral Abutment Bridge (IAB), when possible to do, reduces the cost of construction and maintenance because expansion joints and bearings are not necessary. With the development of reliability approach, it is possible to develop a probabilistic analysis of a structure to study the behavior of the bridge in a more realistic way. A big effort has done in the present years to realize different reliability studies on bridges, but only focused on gravitational loads, without paying much attention to temperature, creep, shrinkage and the interaction of the soil and the structure by the stiffness of the soil around the infrastructure. This work will develop the state of art on literature for the study of this kind of variables in a probabilistic analysis of IAB.

2016 - Comparison of direct and iterative methods for model updating of a curved cable-stayed bridge using experimental modal data [Relazione in Atti di Convegno]
Briseghella, Bruno
abstract

In the paper both a direct method and a sensitivity-based iterative method have been applied to update a finite element model of a curved cable-stayed bridge. The direct method is known as the Douglas-Reid algorithm. The sensitivity-based method is a Trust-Region algorithm. Thirteen experimental modes identified between 0 and 10 Hz under ambient condition have been considered as reference modal data. An a-priori finite element model has been implemented by using the SAP2000 software. The model has been firstly manually tuned and then updated through computational procedures implemented in MATLAB. The results of the direct and the iterative methods have been compared to each other for the specific case study.

2016 - Curved deck arch bridges supported by an inclined arch [Relazione in Atti di Convegno]
Fenu, L.; Congiu, E.; Briseghella, B.
abstract

Curved arch bridges with curved deck supported by an inclined arch either through web members or without are studied. Reference to shell-supported bridges is first made. It must be taken into account that even if the deck is supported by a shell, its bottom free edge (usually stiffened) is described by a thrust line, so that the shell connects the curved deck (that is a horizontal arch) with an inclined 3D funicular arch. A limit case is that the ring girder of the curved deck and the funicular arch merge dividing the shell into two parts, so that, if shell thickness tends to zero, no shell connects them. This is the case of curved bridges supported only at mid-span by an inclined arch. The efficiency of different arches is compared. Moreover, the deck can be supported not only at mid-span but also by web members connecting deck girder and inclined arch. In this latter case, the most appropriate form of the inclined arch is obtained.

2016 - Experiment and calculation on torsion bearing capacity of concrete composite box section with corrugated steel webs and steel truss webs [Articolo su rivista]
Briseghella, Bruno
abstract

To investigate the torsion behavior of concrete composite box sections with corrugated steel webs and steel truss webs, the torsion bearing capacity experiments were carried out. It is found that the diagonal cracks, perpendicular to the principal tensile strains of concrete, first appeared at the bottom plate. Then the cracks spirally developed at both the top and the bottom plates, and the angle between the cracks and the longitudinal axis of the main girder was approximately 45 degrees. Eventually, some larger diagonal cracks were observed at the bottom plate, and the specimens failed by torsion damage after steel rebar yielded in tension. The nonlinear finite element analysis (FEA) for torsion test specimens was simulated using finite element software ANSYS, and the results obtained by FEA agreed well with test results. The cracking torque formula of composite box sections was proposed with reference to the formula of concrete box girders. Using the variable-angle spatial truss model for concrete box girders, the formula of the ultimate torque for composite box sections was established according to the three probable torsion failure modes. In comparison with the results of model test and finite element analysis for actual structural size, the proposed formulas of torsion bearing capacity of concrete composite box sections with corrugated steel webs and steel truss webs had high accuracy, and the maximum error was less than 10%. The proposed formulas can be applied in practical bridge calculation.

2016 - Finite element model updating of canonica bridge using experimental modal data and genetic algorithm [Articolo su rivista]
Liu, T.; Zhang, Q.; Zordan, T.; Briseghella, B.
abstract

This paper calibrates the finite element model (FEM) of a tied-arch bridge using an automatic model updating procedure developed within two softwares. The former is used for sensitivity analysis and optimization analysis while the latter is responsible for structural modeling and eigenvalue analysis. An interface connecting two softwares is first developed, as well as the procedure to calibrate the FEM. Based on the original drawing and topographic survey, the FEM of the investigated bridge is created. To obtain the experimental modal parameters, eight global modes of the studied bridge are identified by ambient vibration tests and the frequency domain decomposition technique. Then, the sensitivity analysis and FEM updating procedure is conducted and the optimal structural parameters are identified. Finally, the updated FEM is verified by a series of static tests. Results show that the updated model could better represent the actual bridge. Therefore, the numerical model updated by the proposed procedure could be further used for damage identification of the bridge under service loads.

2016 - Flexural behaviors of composite continuous box-girder with corrugated steel webs, double concrete filled steel tubular chords and concrete slabs [Articolo su rivista]
Briseghella, Bruno
abstract

A new composite structure composed of corrugated steel webs (CSW), double concrete filled steel tubular chords (CFST) and concrete slabs (CS) was presented. To understand the flexural behaviors under positive and negative bending moments, the experiments of new composite continuous box-girder were carried out, and the failure modes and deflection patterns of the girder, and the development rules of concrete plate cracks were studied. According to the test results, the calculation methods of deformation and bearing capacity of the new type of composite girder were put forward and verified. Experimental result shows the strain peak values of mid-span and intermediate support are only 3.7% and 5.1% of the value of bottom steel concrete pipe chord respectively, therefore the longitudinal strains of corrugated steel webs are small and negligible in the positive and negative bending moment areas. The longitudinal strains linearly change along the height of cross section, thus the plane cross-section assumption can be applied in the composite girder. Moreover, the top concrete flange and the bottom steel concrete pipe chord bear load together. When the cracking load is 140 kN, the calculated and experimental deflection are 5.8 mm and 5.5 mm, respectively, and the relative error is about 5%. When the load of mid-span cross section of test beam reaches the ultimate flexural capacity, the theoretical and experimental load are 399 kN and 415 kN, respectively, the experimental value is slightly higher than the calculated value, but the error is very small and about 4%, so the theoretical calculation methods of deflection and flexural capacity of composite beam are simple and reliable.

2016 - Improve the sustainability of a bridge during the retrofitting [Relazione in Atti di Convegno]
Munoz, M.; Iuliano, M.; Yadav, R.; Chen, B.; Briseghella, B.
abstract

Integral abutment bridges [IAB] represent a structural alternative solution better than conventional solutions for bridges with clear length less than 60 meters. The benefits of this typology, compared to simply supported bridges (“conventional bridge” used in this paper) are: reduction of inspection and maintenance due to the absence of expansion joints and bearings; reduction of risk of failure under seismic loads and an improvement in terms of flood water management. The aim of this work is to evaluate the benefits of retrofit on an existing common bridge, converting it into an integral abutment bridge. Due to this procedure, an increase of sustainability of the bridge will be reached. Some evaluations, about previous works, in the matter of assess of sustainability in civil constructions are used, to compare the advantages of retrofit on a simply supported bridge, changing it into an integral abutment bridge. A practical example is provided.

2016 - Optimal design of pile foundation in fully integral abutment bridge [Capitolo/Saggio]
Xue, J. Q.; Briseghella, B.; Chen, B. C.; Zhang, P. Q.; Zordan, T.
abstract

In order to resolve the durability problem of expansion joints and bearings, the integral abutment bridge (IAB) has become more and more popular. For integral abutment bridge, choosing a suitable pile foundation type is a challenging problem, because the substructure is fixed with superstructure to bear the load together. In this paper, the design of the pile foundation in a fully integral abutment bridge (FIAB) in China was analyzed. A finite element model was built by the commercial software MIDAS considering soil-structure interaction and construction stage simulation. A sensitive analysis was carried out to investigate the influence of different pile foundation types on the mechanic performance of the IAB. The results show that when the circular pile is used, the stress of pile, negative moment and tensile stress of girder are smaller than those when the rectangular pile is used. With the increase of pile diameter, the stress and displacement of pile decrease, while the bending moment of pile and the negative moment and tensile stress of girder increase. For rectangular piles, with the increase of crosssectional length-width ratio, the bending moment of pile, negative moment and tensile stress of girder decrease; while the stress and displacement of pile increase.

2016 - Optimization Indexes to Identify the Optimal Design Solution of Shell-Supported Bridges [Articolo su rivista]
Briseghella, Bruno
abstract

As a structural optimization technique, topology optimization is an important tool for helping designers to determine the most suitable shape of a structure. With this powerful tool, designers can define families of candidate solutions by modifying the input volume reduction (VR) ratio, reducing the structural weight as much as possible. However, finding the best compromise between material savings and structural performance among these candidate solutions is a critical issue for designers. To deal with this issue, an optimization index (OI) is presented in this paper. It provides a mathematical procedure that highlights the best choice among several candidate solutions obtained by the optimization procedure. The index was originally defined in a previous study on the structural optimization of composite steel-concrete bridges. In this paper, a generalized version of the original optimization index is introduced and used to investigate a particular aspect related to concrete shell-supported bridges. Starting from three shell-supported footbridges, the shapes of which are the final result of form-finding optimization procedures, different starting models are defined, and each is characterized by different edge-stiffening conditions. Despite using an anticlastic shell shape, unavoidable tensile stresses occur because of the thickness of the shell, variations in the material, the loading of the deck, and other factors. For each starting model, a finite-element topological optimization conducted with the solid isotropic material with penalization (SIMP) method is performed to minimize the weight (i.e., volume) of the shell by a certain percentage. According to the results obtained from topology optimization, the proposed generalized optimization index (OI∗) analytical formulation is discussed in detail, and its effectiveness is validated.

2016 - Semi static loads in an integral abutment bridge [Relazione in Atti di Convegno]
Munoz, M.; Briseghella, B.; Nuti, C.; Xue, J.
abstract

In order to solve the durability problem of expansion joints and bearings, Integral Abutment Bridges (IAB) have become more and more popular. Soil Structure Interaction (SSI) is a factor that conditions the possibility of the construction of a new IAB, or the retrofitting of an existing from a simply supported bridge into an IAB. Under imposed actions, e.g., horizontal expansion and contraction induced by thermal variation and time-dependent effects (creep and shrinkage), the connection between a super- And substructure responding as a frame structure makes IABs different from other conventional bridges that introduce forces due to SSI. Therefore, the overall horizontal stiffness is mainly due to i) the piles' stiffness, which is usually flexible enough to allow for the deformation of the superstructure and strong enough to carry out the vertical loads, and ii) the type of soil behind the bridge abutment, which has a different stiffness depending on its compaction and composition. Several approaches have been proposed in the literature to consider these types of interaction. In this paper, the accuracy of different formulations commonly used in IABs' design and based on p-y curves and the cantilever method was evaluated. Formulations for piles and abutments were first introduced. Then, a fully integral abutment bridge built in China was considered as a case study. A finite element model of the bridge using SAP2000 software was implemented, and the influence of different methods and formulations was investigated. Finally, the obtained results for different types of soil and approaches were compared and discussed.

2016 - Test study on residual stress distribution of hybrid steel u-rib stiffened plates [Articolo su rivista]
Briseghella, Bruno
abstract

Orthotropic steel bridges were found to experience early fatigue failures of several welded connections in the steel deck plate. The welding process inevitably produces welding residual stresses and deformations that should be evaluated and considered to better understand the fatigue life of steel bridges. Aiming to study the residual stress distribution of hybrid steel u-rib stiffened plates, the blind hole method was applied. Various parameters, including the plate widths, the ratio of the u-rib thickness to the motherboard thickness, and the steel strength of the combination of the u-rib with the motherboard, were considered, and nine specimens were subjected to experimental tests. The results indicate that strain release factors have great impact on the calculated residual stress: as the value of strain release factor increases, the calculated residual stress in absolute term increases accordingly. However, due to experimental errors, as the ratio of the motherboard to the u-rib thickness varies from 1:2 to 1:2.5 and the u-rib spacing increases from 120 mm to 160 mm, the residual stress value and the distribution change are not obvious; when different steel strengths were used in the specimens, as the material yield strength of the motherboard (u-rib) increases, the residual tensile stress peaks of the motherboard (u-rib) increase, while the residual tensile stress distribution of the u-rib (motherboard) remains essentially the same. Based on the comparison between the cutting method and the blind hole method, the values from residual stress test points appear to be similar; from the perspective of measuring points' distribution and the directions of the tested residual stress, the cutting method cannot test the weld location, and the residual stress at the measuring point can only be obtained along the cutting direction because the blind hole method can test the weld location residual stress, and the residual stress of the measuring point can be obtained in any direction.

2015 - A repair and retrofitting intervention to improve plastic dissipation and shear strength of Chinese RC bridges [Relazione in Atti di Convegno]
Lavorato, D.; Nuti, C.; Santini, S.; Briseghella, B.; Xue, J.
abstract

In this paper a rapid repair and retrofitting technique for reinforced concrete (rc) Chinese bridges damaged by a strong earthquake, is proposed and tested. This intervention is an upgrade of the one tested with very good results during a previous experimental research on bridges designed according to the old Italian code without proper seismic details. The improvement of the repair operation consists in the use of dissipation systems to substitute the damaged rebar parts at pier base guaranteeing the correct plastic distribution in plastic hinge only. Dissipation systems with different configurations were considered to optimize the intervention. The repaired and retrofitted Italian bridge already studied in the previous research, was designed according to Chinese codes but with insufficient transversal steel reinforcement. Some pier specimens (scale 1:6) of the most stressed pier of this bridge, with and without dissipation systems, were built. A C-FRP wrapping was applied to increase the insufficient shear strength and the ductility in plastic hinge. Cyclic tests were carried out on the scaled specimens at Fuzhou University lab (China) to evaluate the effectiveness of the proposed technique.

2015 - An innovative steel-concrete joint for integral abutment bridges [Articolo su rivista]
Briseghella, B.; Zordan, T.
abstract

Integral abutment bridges are becoming rather common, due to the durability problems of bearings and expansion joints. At the same time, among short- and medium-span bridges, multi-beam steel-concrete composite deck with hot-rolled girder is an economical and interesting alternative to traditional pre-stressed concrete solutions. The two concepts can be linked together to design integral steel-concrete composite bridges with the benefits of two typologies. The most critical aspect for these bridges is usually the joints between deck and piers or abutments. In this paper, an innovative beam-to-pier joint is proposed and a theoretical and experimental study is introduced and discussed. The analyzed connection is aimed at combining general ease of construction with a highly simplified assembly procedure and a good transmission of hogging and sagging moment at the supports in continuous beams. For this purpose, the traditional shear studs, used at the interface between steel beam and upper concrete slab, are also used at the ends of steel profiles welded horizontally to the end plates. To better understand the behaviour of this kind of joints and the roles played by different components, three large-scale specimens were tested and an FE model was implemented. The theoretical and experimental results confirmed the potential of the proposed connection for practical applications and indicated the way to improve its structural behaviour.

2015 - Curved shell-supported footbridges [Relazione in Atti di Convegno]
Fenu, L.; Briseghella, B.; Zordan, T.
abstract

After Maillart's curved bridges, the improved building technologies in structural concrete and steel work led designers to realize different typologies of curved bridges. Jörg Schlaich's contribution in the design of curved bridges has been fundamental, through developing different typologies of suspended and cable-stayed curved bridges. In the '60s of the past century, Sergio Musmeci gave another innovative contribution to bridge design, by shaping shell supported bridges with minimal shell surface, and finally realizing the Basento Bridge in Potenza, Italy, a concrete shell bridge considered as his masterpiece. Accounting for Schlaich's and Musmeci's work on, respectively, curved and shell bridges, a curved footbridge supported by an anticlastic concrete shell with minimal surface is herein studied. The influence of the boundary conditions on bridge shape, and the advantages of prestressing the ring girder supporting the cantilevered deck are studied.

2015 - E-learning, the future of structural engineering education? [Relazione in Atti di Convegno]
Lozano-Galant, J. A.; Briseghella, B.; Zordan, T.; Turmo, J.
abstract

In last years, the traditional blackboard teaching has been supplemented by visual aids like slide projectors and videos. The phenomenal growth of the Internet has brought in new teaching media, such as E-learning. Online courses and multimedia material over the Internet open the educational experience up to distant students without schedule restrictions, making E-learning an attractive option especially for professionals. Nevertheless, the overwhelming amount of material currently available might complicate the offer selection. Furthermore, internet globalization makes that quality levels of these materials might differ significantly. Aware of these problems, IABSE created the E-Learning board to address conveniently the online learning in structural engineering. Recently, the Association has created a new platform that aims to become a leader in quality online education. As a way to promote the use of this platform, the E-learning board proposes a debate focused on how the future of structural engineering education is linked with the different kinds of E-learning in both academia and industry training.

2015 - Equivalent viscous damping of bilinear hysteretic oscillators [Articolo su rivista]
Liu, T.; Zordan, T.; Zhang, Q.; Briseghella, B.
abstract

An improved formula to determine the equivalent viscous damping ratio of a single-degree-of-freedom (SDOF) bilinear oscillator is proposed in this paper, which simultaneously considers the influence of the initial period, ductility ratio, and strain hardening ratio. A large number of parameters are considered in order to present comprehensive results. Based on the assumption of secant stiffness, several equivalent linearization approaches are evaluated through parametric analyses. Then, optimization analyses are performed using a genetic algorithm to identify the variation trend of optimal damping ratios. A new formula of an equivalent viscous damping ratio is proposed by nonlinear regression analyses of the optimal damping ratios. Finally, the proposed approach is validated and the results show that the proposed approach leads to better estimates of maximum inelastic displacement response in the entire parameter space considered in this study when compared with other equivalent linearization approaches.

2015 - Experimental study on K-joints of concrete-filled steel tubular truss structures [Articolo su rivista]
Briseghella, Bruno
abstract

The failure modes of K-joints of Concrete Filled Steel Tubular (CFST) truss structures were investigated through laboratory tests. CFST K-joint specimens consisted of a tubular chord filled with concrete and two braces inclined at the same angle with respect to the chord. Their size was chosen of the same scale as that of joints of real tubular structures currently used in bridges. The results were compared with those obtained by testing K-joint specimens of Circular Hollow Section (CHS) truss structures with the same size. Contrary to CHS K-joints, where a chord face failure mode occurred, in CFST K-joints no failure mode with inward deformation of the chord section can occur. Hence, punching shear failure was shown to be the typical failure mode of CFST K-joints, if no brace failure mode occurred before. Resistance of CFST K-joints to punching shear was then compared with the resistance values calculated through the Eurocode 3 and the AWS code formulae on CHS K-joints. The values provided by the former formula were quite close to (although always lower than) the actual resistance to punching shear of CFST K-joints. Finally, the favourable effect on joint resistance due to additional studs welded to the interior surface of the chord tube of CFST K-joint was also investigated.

2015 - Finite element model updating of a highway bridge based on operational modal analysis [Relazione in Atti di Convegno]
Briseghella, Bruno
abstract

This paper deals with the dynamic identification and finite element model updating of Magaz bridge, located in Spain. It is a three span continuous bridge with composite steel-concrete cross section. Operational modal analysis was performed from ambient vibration data by the covariance driven stochastic subspace identification algorithm. A very accurate three-dimensional finite element model was built using SAP2000 assuming geometrical and mechanical properties from the original drawings. At the first step of the calibration process, a parametric study was performed to identify the most sensitive parameters affecting the finite element model-computed modal frequencies and mode shapes. The automated finite element model updating problem has then been formulated as an optimization problem. The uncertainty on some physical parameters has been adjusted through an iterative process that aims at minimizing the objective function, hence to solve a nonlinear least squares problem which has as its subject the residuals of the relative difference from the numerical and experimental eigenfrequencies and eigenvectors. The outcome of the optimization is a significantly improved finite element model with very good agreement in terms of frequencies and modal assurance criteria values on the first modes.

2015 - Finite element model updating of a highway bridge based on operational modal analysis [Relazione in Atti di Convegno]
Losanno, D.; Iuliano, M.; Briseghella, B.; Serino, G.
abstract

2014 - A discrete bond law for precast panels systems without reinforcement [Relazione in Atti di Convegno]
Briseghella, Bruno
abstract

This paper discusses the possible application of finite element non-linear modelling to a construction system using precast concrete panels. Details are given of the shell elements used for modelling panels and joints, focusing in detail on the non-linear law conferred to the link elements used to represent resistance to relative sliding movement at the interface among panels. The paper relates in particular to an emulative system using cast-in-place joints, without transverse reinforcement. Also the results of pushover analyses, conducted first on a single wall (with the purpose of studying the effect of joint failure on the capacity of the system), then on an entire building erected using the same construction system are presented, assessing the applicability in seismic regions and considering different numbers of storeys.

2014 - An improved equivalent linear model of seismic isolation system with bilinear behavior [Articolo su rivista]
Liu, T.; Zordan, T.; Briseghella, B.; Zhang, Q.
abstract

2014 - Equivalent linearization of bridges with bilinear isolation systems [Relazione in Atti di Convegno]
Zordan, T; Mazzarolo, E; Zhang, Ql; Briseghella, B; Liu, T
abstract

Although maximum displacement demands of bridges can be obtained through non-linear time history analysis, many approximate methods have been proposed in recent codes to reduce the required computational time distinctive of non-linear approaches. Among these methods, equivalent linearization method is best known. This paper evaluates the accuracy of equivalent linearization method adopted in AASHTO through comparison of non-linear and linear time history analysis. The isolation system is characterized by bilinear hysteretic behavior and the bridge is simplified to be a single-degree-of-freedom (SDOF) system. A comprehensive parametric study is performed using a program developed by MATLAB in combination with OpenSees. Results show that the predicted maximum displacement is significantly underestimated by AASHTO method when the strain hardening ratio and ductility ratio are relatively small. To improve the estimation accuracy of equivalent linearization technique, a new equation of equivalent damping ratio is proposed by modifying AASHTO method. © 2014 Taylor & Francis Group.

2014 - Evaluation of equivalent linearization analysis methods for seismically isolated buildings characterized by SDOF systems [Articolo su rivista]
Liu, T.; Zordan, T.; Briseghella, B.; Zhang, Q.
abstract

Although peak response of seismic isolation systems can be obtained through nonlinear time history analysis method, approximate linear elastic analysis method is frequently proposed in recent structural codes to reduce the computational effort and to simplify the design procedure. Of the approximate methods, the equivalent linearization (EL) method is best known. In this study, fourteen EL methods proposed in the literatures are assessed based on single-degree-of-freedom (SDOF). systems with bilinear hysteretic behavior. A large number of numerical simulations are performed using a program developed by MATLAB in combination with OpenSees to evaluate the influence of ductility ratio and initial period on the accuracy of EL methods to estimate the maximum inelastic displacement of bilinear SDOF systems when subjected to 12 earthquake ground motions. A set of 20 ductility ratios ranging from 2 to 50 are considered, as well as 15 initial natural periods between 0.1. s and 1.5. s. Ratios of approximate to exact maximum displacement corresponding to each EL method are averaged over the considered ground motions, and the standard deviation of investigated ratios is also calculated to measure the degree of dispersion. Eventually, comments on the accuracy of different EL methods are given to make their applications more appropriate in practical design of base isolation systems. © 2013 Elsevier Ltd.

2014 - Finite element model updating of a tied-arch bridge using Douglas-Reid method and Rosenbrock optimization algorithm [Articolo su rivista]
Briseghella, Bruno
abstract

Condition assessment of bridges has become increasingly important. In order to accurately simulate the real bridge, finite element (FE) model updating method is often applied. This paper presents the calibration of the FE model of a reinforced concrete tied-arch bridge using Douglas-Reid method in combination with Rosenbrock optimization algorithm. Based on original drawings and topographie survey, a FE model of the investigated bridge is created. Eight global modes of vibration of the bridge are identified by ambient vibration tests and the frequency domain decomposition technique. Then, eight structural parameters are selected for FE model updating procedure through sensitivity analysis. Finally, the optimal structural parameters are identified using Rosenbrock optimization algorithm. Results show that although the identified parameters lead to a perfect agreement between approximate and measured natural frequencies, they may not be the optimal variables which minimize the differences between numerical and experimental modal data. However, a satisfied agreement between them is still presented. Hence, FE model updating based on Douglas-Reid method and Rosenbrock optimization algorithm could be used as an alternative to other complex updating procedures.

2014 - Improved equivalent viscous damping model for base-isolated structures with lead rubber bearings [Articolo su rivista]
Zordan, T; Liu, T; Briseghella, B; Zhang, Ql
abstract

Nowadays, seismic isolation system has been widely applied in the world to mitigate damage risk of structures. Although maximum displacement demand can be obtained through nonlinear time history (NLTH) analysis, many approximate methods are frequently recommended in structural specifications to reduce the required computational time. One of the best-known methods is the equivalent linear (EL) method, in which the nonlinear response of isolator can be adequately modeled using a fictitious viscously damped elastic structure. In this paper, a comparison between existing expressions supplying the state of research is carried out and then, an improved expression is presented for equivalent linearization of structures supported on lead rubber bearings (LRB). Based on the concept of secant stiffness, the optimal damping ratios, which minimize the errors of maximum displacement between EL analysis and NLTH analysis, are calculated and averaged over 12 ground motions. Then, a rational model to estimate equivalent damping ratio is derived through statistic analysis of the optimal damping ratios. To examine the prediction accuracy of the proposed model, mean ratios of approximate to exact maximum displacement and root mean square error for different isolated period are calculated as evaluation indicator. Compared with other EL models, the newly proposed model predicts a displacement that is in better agreement with the one obtained through NLTH analysis. © 2014 Elsevier Ltd.

2014 - Influence of substructure height on fully integral abutment bridge in sand [Relazione in Atti di Convegno]
Briseghella, Bruno
abstract

Nowadays, many simply supported bridges constructed all over the world have been affected by the durability problems, especially broken expansion joints and damaged bearings. In order to resolve fundamentally the durability problems of existing bridges during their service life, the concept of integral abutment bridge came out. In this paper, the retrofit technology with the concept of integral abutment bridge was analyzed, based on a simply supported bridge "Viadotto Serrone" in Italy. The corresponding finite element models of the existing jointed bridge and four types of fully integral abutment bridges after retrofit were built by Sap2000. Using the finite element model, the sensitive analysis choosing the substructure height as the critical influential factor was carried out. Some regulations obtained can be adopted as the guideline of this retrofit technology.

2014 - Italian national road authority IABs strategy [Relazione in Atti di Convegno]
Xue, J. Q.; Briseghella, B.; Chen, B. C.; Zordan, T.; Mazzarolo, E.
abstract

Many simply supported bridges have been constructed all over the world. The majority of them have been affected by some durability problems during their service life. For this purpose, the concept of integral abutment bridge came out which can achieve the requirement of road administrations to resolve the durability problems of broken expansion joints and damaged bearings fundamentally. In this paper, a retrofitting technology using the concept of integral abutment bridge and developed for the Italian National Road Authority (ANAS) is presented. A typical simply supported bridge "Viadotto Serrone" in Italy was chosen as case study. The corresponding finite element model was built by Sap2000 considering some critical issues, such as soil-structure interaction, plastic hinge assignment, foundation modeling and retrofitting process simulation. In order to find out the most critical influential factors and useful regulations which can be adopted as the guideline of this retrofitting technology, the influence of the new Italian codes on the mechanical properties of different types of bridge, including the simply supported bridge without rehabilitation and integral abutment bridges after retrofitting, were investigated using finite element model. © 2014 Taylor & Francis Group.

2014 - Optimization of Calatrava bridge in Venice [Relazione in Atti di Convegno]
Zordan, T.; Mazzarolo, E.; Briseghella, B.; Chen, B. C.; Feng, Y.; Siviero, E.; Fenu, L.
abstract

Structural optimization has become an important tool for structural designers. It helps them to find innovative design solutions and structural forms with a better exploitation of materials as well as decreased structures' self-weight and minimum material costs. In this article, the Calatrava Bridge over the Grand Canal of Venice is used as a prototype. Several tentative starting models are identified by considering bridge's abutment deformability through spring-damper elements and introducing prestressing stiffening cables along two bottom arches of the bridge. Afterwards members' thickness optimization is carried out and the results are compared in terms of weight reduction and horizontal force level. The results evidence that thought the use of structural optimization, more reasonable thickness distribution of steel members can be obtained, while reducing remarkably both the self-weight and the horizontal forces of this bridge against the abutment. © 2014 Taylor & Francis Group.

2014 - Seismic analysis of a concrete filled steel tubular truss bridge [Relazione in Atti di Convegno]
Briseghella, Bruno
abstract

During the recent construction activity in China, concrete filled steel tubes (CFST) typology is innovatively applied in beam bridges with CFST composite truss girders and CFST lattice piers. The subject is Ganhaizi Bridge, one of the most unusual viaducts, has a total length of 1811m and is an experimental truss bridge that uses steel tubes for nearly the entire structure. This paper presents the study on nonlinear seismic performance of Ganhaizi Bridge. Seismic response characteristics, piers yielding order and internal force redistribution effect in plastic scope are investigated through a simplified fiber finite element model based on the second unit of this bridge. Take extreme edge strain of CFST columns as criterion, the horizontal most adverse seismic input direction for this curved bridge is perpendicular to the bearing connection on both ends, the influence of vertical ground motion should be simultaneously considered. After turn into plastic stage with increasing peak ground acceleration (PGA), the main stress direction of lattice piers and composite piers are both in plane, axial forces increase less than seismic, while displacements increase greater. Bending moments of high piers increase greater than short piers, which is expected to facilitate seismic performance of the whole bridge.

2014 - Shaking table tests for the evaluation of the seismic performance of an innovative lightweight bridge with CFST composite truss girder and lattice pier [Articolo su rivista]
Briseghella, Bruno
abstract

The seismic performance of an innovative lightweight bridge with CFST composite truss girder and lattice pier was studied in this paper. Took Ganhaizi Bridge as prototype, a 1:8 scale specimen with two spans and three lattice high piers was designed for multi-shaking tables test. Adopted design seismic wave of prototype, dynamic characteristics, seismic performance and failure characteristics were analyzed. Results indicate that the frequency ratio and the displacement ratio between specimen and prototype are corresponding to similitude relationship. Under transverse or longitudinal excitation, acceleration in lattice zones significantly amplifies, and decreases the acceleration of the deck. It is unnecessary to consider the influence of bi-directional excitations. Displacement on the top of pier is less than the value limitation under design ground motions. The corresponding finite element simulations, using OpenSees, were carried out and the accuracy was verified. The finite element analysis results agree with experimental data. In addition, the plastic hinges were predicted under transverse and longitudinal excitation respectively, revealed that lightweight bridge with CFST composite truss girder and lattice pier has a favorable seismic performance. © 2014 Elsevier Ltd.

2014 - Simplified linear static analysis for base-isolated buildings with friction pendulum systems [Articolo su rivista]
Liu, T.; Zordan, T.; Briseghella, B.; Zhang, Q.
abstract

Several methods of analysis used for the design of base-isolated buildings are proposed in many structural specifications. According to different structural codes, limited conditions of equivalent linearization of the friction pendulum system (FPS) and application scopes of simplified linear static analysis (LSA) are introduced. LSA of a reinforced concrete frame building isolated by FPS is performed and compared with fast nonlinear time-history analysis (FNA) to evaluate the suitability of the simplified method. Based on a specific spectrum used in the new Italian code, seven spectrum-compatible earthquake ground motions are selected and scaled as seismic input. To perform both linear and nonlinear analyses systematically, a program is specially developed by MATLAB in combination with a commercial software. Base displacement, story shear force, and energy dissipation are selected as response indicators. The results reveal that, as a substitute for the exact nonlinear analysis method in the preliminary design of base-isolated buildings, the LSA method yields conservative estimates in base displacement and total input energy. However, because of the uniform acceleration profile assumed over the structural height, the story shear forces are significantly underestimated by LSA.

2014 - Technical research on the seamlessness and continuity transformation of existing multi-span simply-supported hollow slab bridge [Relazione in Atti di Convegno]
Briseghella, Bruno
abstract

For an existing multi-span hollow slab bridge, its distress and safety have been investigated and analyzed. Based on the reviewing of current prevailing reinforcement schemes, this paper puts forward a new kind of reinforcing scheme-transformation from the simply-supported beam to a seamless and continuous structure. Its pros and cons, as well as its implementation plan and calculation method, are respectively introduced. Finally, this paper introduces the short and long term monitoring plan for the bridge's construction and performance. © 2014 Taylor & Francis Group.

2013 - Application of topological optimization to bridge design [Articolo su rivista]
Briseghella, B.; Fenu, L.; Lan, C.; Mazzarolo, E.; Zordan, T.
abstract

Recently, structural optimization has become an important tool for structural designers, because it allows a better exploitation of material, thus decreasing a structure's self-weight and saving material costs. Moreover, structural optimization helps the designer to find innovative design solutions and structural forms that not only better exploit material but also give the structure greater aesthetic value from an architectural point of view. In this article, the seismic retrofitting of a bridge originally designed in reinforced concrete is illustrated, showing how lightening the bridge superstructure, rather than reinforcing the already completed foundations and abutments, allowed these latter features to resist greater seismic actions as required in the recent update of the Italian seismic code. Therefore, besides using the steel-concrete composite typology, the bridge superstructure was lightened through structural optimization. After having optimized the thickness of webs and flanges, it was necessary to further lighten the bridge superstructure by removing unexploited material from the bottom flange through the insertion of large cavities. For this purpose, topology optimization is shown to be a powerful tool that allowed the designer to find that the hole shape was basically elliptic, thus suggesting their regularization as ellipses. Comparisons were made between several design solutions, each characterized by a specific volume reduction of the bottom flange. Identification of the highest-performing solutions through computer-aided procedures led to a weight reduction of 40% with respect to the design solution in reinforced concrete. Retrofitting the already existing foundations and abutments to satisfy the updated provisions of the new seismic code was thus avoided by defining an innovative layout of arch bridges with holes in the bottom flange, which has never been used before. © 2013 American Society of Civil Engineers.

2013 - Friction pendulum system as a retrofit technique for existing reinforced concrete building [Articolo su rivista]
Briseghella, B.; Zordan, T.; Liu, T.; Mazzarolo, E.
abstract

Friction pendulum system (FPS) is one of the most effective base isolation systems, which is widely used for seismic upgrading of existing buildings. FPS is almost always non-linear and often strongly non-linear, so a mechanical model of FPS bearing is of great importance in seismic analysis. In this paper, three different models of FPS bearing are described and a building severely damaged by the L'Aquila earthquake in 2009 is examined according to the latest Italian code. Then, a case study presenting briefly an innovative technique that is able to introduce base isolation on existing buildings is provided with reference to the use of FPS. Different kinds of analyses, including response spectrum analysis and linear and non-linear dynamic analyses, are performed under the life-safety limit state. Storey shear, inter-storey drift, effective stiffness and energy dissipation are the considered parameters to investigate the effectiveness of the retrofitting procedure and analysis techniques.

2013 - Topology optimization of bridges supported by a concrete shell [Articolo su rivista]
Briseghella, B.; Fenu, L.; Feng, Y.; Mazzarolo, E.; Zordan, T.
abstract

A shell-supported footbridge was designed by shaping an anticlastic membrane in compression between deck and foundations. Since it would be subject to biaxial compression, it was appropriate to be made of concrete because concrete strength could be exploited and crack propagation prevented. With reference to Musmeci's work, a form-finding algorithm shaped the shell as a tension structure with same loads, restraint reactions and internal normal forces, but with the opposite sign. Using a finite element (FE) model of the shell, unwished bending moments (and therefore tensile stresses) were, however, found, because of second order displacements and (contrary to a tension structure) because of the bending stiffness of the reinforced concrete (RC) shell. Tensile stresses were progressively eliminated by removing material from the shell regions where unwished bending moments occurred. For this purpose, topology optimization with the Solid Isotropic Material with Penalization (SIMP) method was used, and different shell structures with cavities for different values of given volume reduction were obtained. Appropriate indexes for structural response were defined, and an optimization index was finally used to identify the most suitable pattern of cavities along the shell.

2012 - Analysis on applicability of health monitoring techniques on a curved cable stayed bridge [Relazione in Atti di Convegno]
Briseghella, B; Chen, A; Li, X; Zordan, T; Lan, C; Mazzarolo, E
abstract

Theoretical and experimental investigation (ambient vibration tests and permanent monitoring system) on the structural behavior of a curved cable-stayed bridge is presented in the paper. The investigated bridge - erected in the Commercial Harbor of Marghera (Venice, Italy) - was opened to traffic on January 2007 and includes six generally curved spans, where the two main (105 m + 126 m) spans are suspended by cable-stays, connected to the centerline of the deck. As a consequence of the spatial structural arrangement, the dynamic behavior of the deck appears very complex in both bending and torsion. In this paper, based on the experimental dynamic tests on a curved cable-stayed bridge carried out during construction phase in May 2006 and during public service in July 2010, finite element model was built and tuned accurately according to comparisons between experimental and theoretical analyses. Then, analyses were performed to investigate the applicability of monitoring techniques on the modal parameters, deformation, stress, and strain. In the end, suggestions and recommendations on the bridge monitoring system were discussed and presented. © 2012 Taylor & Francis Group.

2012 - Bond slip model for generalized excitations [Relazione in Atti di Convegno]
Mazzarolo, E.; Zordan, T.; Briseghella, B.
abstract

Correct evaluation for bond-slip effects is a crucial point when investigating progressive damage of reinforced concrete structures under random or earthquake excitations. For bridges, this aspect affects in particular the seismic response of piles' base and pier-deck joint in Integral Abutment Bridges as well. The need for a bond model, more accurate than those currently available in literature, without renouncing to ease of implementation, suggested to develop a new one. This model is defined by summing the effects of different bond resistance contributes (namely mechanical bond, friction bond and virgin bond) defined by means of continuous functions. This allows to fit, with reasonable precision, experimental monotonic and cyclic bond-slip paths, even along reloading branches. New relationships have been provided for updating the main law parameters at each load reversal. Moreover a specific progressive damage rule is introduced, able to account for generalized excitation. The proposed law has been validated by comparison with several existing pull-out cyclic data obtained from short-anchorage tests in good confinement conditions. © 2012 Taylor & Francis Group.

2012 - Effects of debonding on circular CFST stub columns [Articolo su rivista]
Xue, J. -Q.; Briseghella, B.; Chen, B. -C.
abstract

Core concrete subjected to confinement effect from steel tube is the main advantage of concrete filled steel tubular (CFST) column under compression. However, this beneficial composite action could be weakened even destroyed by debonding, which is almost unavoidable as a common phenomenon in CFST structures and has not been considered satisfactorily by current design codes. In this paper, the influence of debonding on circular CFST stub columns was investigated experimentally and numerically. The main experimental parameters were the debonding arc-length ratio, the confinement factor and the load mode. Meanwhile, the finite element models were implemented using the ABAQUS finite element software, of which the validity and accuracy were verified by test results. Utilising the finite element model, the parametric analysis was carried out to study the influence of the following parameters on the ultimate load capacity of debonding specimens: debonding arc-length ratio, debonding thickness and confinement factor. Based on the results of parametric analysis, a simplified calculation formula was proposed to calculate the ultimate load capacity of circular CFST stub columns with debonding. © 2011 Elsevier Ltd. All rights reserved.

2012 - Experimental study on the ultimate load-carrying capacities of concrete filled steel tube battened columns [Relazione in Atti di Convegno]
Chen, B.; Yan, Q.; Song, F.; Briseghella, B.
abstract

Concrete filled steel tube (CFST) built-up columns have been widely used as building columns, bridge piers and arch ribs in civil engineering. Much research progress has been made on them; however, attention was just focused on CFST laced columns, not on CFST battened columns. In this paper, experiments on 29 CFST battened columns are carried out. The test parameters are load eccentricity, slenderness ratio, chord spacing and batten spacing. The whole loadbearing process, the failure modes and the ultimate load-carrying capacities of the specimens are analyzed. The studies show that the eccentricity and slenderness are the two main parameters independently affecting the load-carrying capacities of CFST battened columns. Therefore, the partial safety factor to predict the reduction effect in DBJ/T code for CFST laced column is suggested to be used for CFST battened column. However, the CFST battened column has lower resistance to shear than that of the CFST laced column, the calculation method of equivalent slenderness ratio for the CFST laced columns cannot be applied directly for the CFST battened columns. The magnifying factor K for steel battened column, which is called M-K method, is introduced to calculate the equivalent slenderness ratio for CFST laced columns.

2012 - Seismic analysis of a rigid frame continuous cfst truss girder bridge with composite piers [Relazione in Atti di Convegno]
Huang, Y.; Wu, Q.; Chen, B.; Briseghella, B.
abstract

The elastic seismic response characteristics of a rigid frame continuous CFST truss girder bridge with composite piers are studied with Finite Element (FE) method based on the commercial software MIDAS/civil. The FE results show that the fundamental respond mode of the bridge is a longitudinal mode with a frequency of 0.268 Hz, indicating the bridge is flexible enough to resist seismic activation due to its light self-weight The critical regions are in the elastic range under the most unfavorable direction of ground motion, and the resistance requirement in moderate ground motion is satisfied. The longitudinal and lateral displacements on top of the piers are examined, and it is found that the displacement limit for the CFST pier needs further discussion.

2012 - Static behaviour of a prestressed stone arch footbridge [Relazione in Atti di Convegno]
Huang, W.; Fenu, L.; Briseghella, B.; Chen, B.; Zordan, T.
abstract

A twin-arch rib footbridge constructed with innovative use of prestressed stone ashlars is designed and its static behavior is investigated by finite element method. Through FE spatial and plane models, general deformation modes, contact-sliding behavior of the interface between stone element and mortar layer, as well as stresses in the stone arch ribs under crowd load are investigated. It is revealed that FE plane model can accurately analyze the bridge's general deformation. Conversely, from the analysis of FE spatial models, no separation or sliding between stone element and mortar layer has been found under critical load cases. Moreover, stress control in the different materials is also achieved. Finally, both geometry and structural layout of the new-type structure are technologically feasible.

2012 - Topology optimization with eigenfrequency of concrete shell bridge [Relazione in Atti di Convegno]
Briseghella, B.; Yue, F.; Fenu, L.; Siviero, E.; Zordan, T.; Chen, B.
abstract

Shell supported bridges whose deck is supported by a shell structure are special spatial bridge structures shaped by means of a form-finding algorithm. In order to achieve mainly membrane stresses and avoid bending effects, Zordan et al.(2010) carried out a finite element topological optimization procedure by means of the SIMP (Solid Isotropic Material with Penalization) method, with the goal of minimizing compliance^]. Meanwhile, although eigenfrequency optimization applied to shell structures is infrequent, the topological optimization procedure can be also used to maximize the fundamental natural frequency of shell structures, and is also effective in reducing the arising of tensile stresses. In this paper, starting from a shell surface obtained through a form-finding process and that supports the deck of a footbridge, the finite element topological optimization with eigenfrequency was carried out by using the SIMP method to both maximize the fundamental natural eigenfrequency and minimize of a certain percentage the weight (volume) of the shell itself. Topological optimization through the SIMP method first identified the shell regions with lower pseudo densities, while the geometry of the shell was updated by eliminating the inefficient material in these regions. Although maximizing the fundamental eigenfrequency with topological optimization is not so effective compared to other slender structures because of the intrinsic stiffness of the concrete shell structure itself, the area of shell regions where tensile stresses arose was however clearly minimized.

2011 - Analytical formulation for limit length of integral abutment bridges [Articolo su rivista]
Zordan, T.; Briseghella, B.; Lan, C.
abstract

The integral abutment bridge concept has recently become a topic of remarkable interest among bridge engineers, not only for newly built bridges but also for refurbishment processes. The sup er-structure of integral abut ment bridges (IABs) is made continuous through composite cast-in-place concrete deck slabs over pre-stressed concrete or steel girders. The system constituted by the substructure and the super-structure can achieve a composite action responding as a single structural unit; this princi ple is applicable also while converting existing simply supported bridges into IABs. Several guidelines for the design of IABs have been published in the last few years. The main idea is to introduce designers to this kind of structures thereby limiting the total length, skewness and inclination of the deck. The maximum length usually recommended for this kind of structures is around 100 m or less. This limitation is derived from the difficulties introduced by the need to control the soil- structure interaction for imposed temperature variations: This is the main factor affecting increasing of the overall length of the structure. Achieving the maximum length attainable with this kind of structures is intrinsically related to a thorough understanding of the soil- structure interaction behind the abutments or next to the foundation piles. It has been proved that the maximum allowed length for IABs is 400 m. The world record for the longest IAB, which represents the transformation of a simply supported flyover in Verona, Italy, will be discussed in this paper together with the non-linear parametric analyses carried out to determine the solution presented. The paper will deal with the possibility of achieving super-long IABs using standard pre-fabricated cross sections and typical reinforcement ratios for foundation elements and super-structure.

2011 - Parametric and pushover analyses on integral abutment bridge [Articolo su rivista]
Briseghella, Bruno
abstract

Integral abutment bridges (IABs) are jointless bridges where the girder or the deck is continuous and monolithically connected to the abutments. A usual and important problem in the design of IABs is how to deal with the soil-structure interaction behind the abutments and next to the foundation piles: this can be considered as a fundamental aspect to reach a thorough understanding of this type of structure, which requires iterative and nonlinear analysis. In this paper, a 2D simplified finite-element model of a real 400-metre-long IAB, built in the Province of Verona-Italy, is implemented and used to perform non-linear analyses on the bridge, the structural response of which is then examined in detail. A parametric study based on the variation of the soil properties behind the back-walls and around the piles is then performed. Furthermore, a temperature pushover analysis (non linear static analysis for positive and negative temperature variations) is carried out to assess the failure pattern of the bridge caused by a temperature change, considered as one of the key parameters in IAB design. Lastly, the effect of abutment stiffness is also discussed. © 2010 Elsevier Ltd.

2010 - Bridge structural optimization through step-by-step evolutionary process [Articolo su rivista]
Zordan, T.; Briseghella, B.; Mazzarolo, E.
abstract

In this paper, the structural optimization process aiming to reduce the weight of the superstructure of a five span arch bridge, built in the Province of Venice, Italy, and spanning the Piave River in the town of San Donà, is presented. The original project, with a pre-stressed concrete superstructure, was re-considered during construction because of the following two unexpected events. First, the approved new seismic national regulation became effective when the bridge was already partially built. As a result, existing foundations became unable to withstand the prescribed new seismic action. Furthermore, the Venice Water Authority, responsible for the management of the river spanned by the bridge, declared that erection phases without any provisional supports and scaffolding , resting on the riverbed, as foreseen by the original project, should be preferred. Between the two possible identified design strategies able to deal with the mentioned problems, namely, the strengthening of the foundations or the lightening of the superstructure, the second option was chosen, on the basis of engineering judgement concerning the simplification of construction procedures, timing and budget. The search for the lightest possible solution, with the restraint given by the approved aesthetics of the original design and the need of keeping within the former budget, brought to the conclusion that an evolutionary structural optimization (ESO) process could be suitably applied to a composite steel and concrete superstructure.

2010 - Cyclic behaviour of prefabricated high-strength concrete composite beam-to-column joints [Relazione in Atti di Convegno]
He, J.; Zordan, T.; Chen, A.; Briseghella, B.; Ma, R.; Ruan, X.; Mazzarolo, E.
abstract

Prefabricated high-strength concrete composite beam-to-column joints were widely used in civil engineering. Six full scale cruciform type test samples with different parameters (thickness of steel joint plate and reinforcement ratio of column) were constructed and tested under cyclic lateral loading to study on the hysteretic behavior. The load-displacement curves, failure mode, stiffness degradation and energy dissipation capacity were presented. It was found that the strength and stiffness are less influenced by the steel joint plate thickness, but more influenced by the reinforcement ratio of the column. Failure modes were transformed from brittle shear in the column diagonals to a ductile one in the beam region, more ductile behavior and slower stiffness degradation were observed for the specimens strengthened by CFRP materials. The findings from the analysis were of guiding significance to the design and construction of the composite joint.

2010 - Experimental research on debonding in concrete-filled steel tubes columns subjected to eccentric loading [Relazione in Atti di Convegno]
Xue, J.; Chen, B.; Briseghella, B.
abstract

Concrete core subjected to confinement effect from steel tube is the main advantage of concretefilled steel tubular (CFST) column under compression. However, the debonding of concrete to steel tube which is a common phenomenon in real structures will have an unfavorable effect on the confinement. In this paper, the influence of debonding on CFST stub columns subjected to eccentric loading was investigated experimentally. The debonding gap was formed by inserting galvanized sheet in the steel tube before the concrete fill and by pulling them out after 5~6 hours. From the test, it was verified that the method to form the debonding gap of specimen is valid. The parameters in the test included the debonding arc-length ratio and steel ratio. All the specimens failed in flexural mode, which indicated that the debonding has no influence on the failure modes. The ultimate load capacity and the ductility of the specimens were significantly decreased with the increased debonding arc-length ratio, while this unfavorable influence would decrease with the steel ratio increase.

2010 - Optimized design for soil-pile interaction and abutment size of integral abutment bridges [Relazione in Atti di Convegno]
Briseghella, B.; Lan, C.; Zordan, T.
abstract

In the last few years, the integral abutment bridge (IAB) concept has become quite common. It is, incidentally, not a newly developed concept, its formulation dating back at least to the 1930s, in order to deal with long-term structural problems frequently occurring with conventional bridge design. At present, the IAB concept is generating considerable interest among bridge engineers because of the enormous benefits due to elimination of expansive joints and reduced installation and maintenance costs. The superstructure of integral abutment bridges is made continuous through a composite cast-in-place concrete deck slab over prestressed concrete or steel girders and continuity diaphragms, and the system constituted by the sub- and the super-structure acts as a single structural unit. A usual and important problem in the design of IABs is how to deal with the soil-structure interaction behind the abutments or next to the foundation piles: this can be considered as a fundamental aspect for the thorough understanding of this type of structures, which requires iterative and nonlinear analysis. In this paper, a 2D simplified finite-element model of a real 400 meters long IAB, built in the Province of Verona-Italy, will be implemented and used to perform non linear analysis on the bridge. Then, based on the results obtained from a parametric study on the IAB, the analysis of effects of soil-pile interaction and the abutment size will be carried out to find out the relative key parameters in IABs design.

2010 - Safety monitoring of the cable stayed bridge in the Commercial Harbor of Venice, Italy [Relazione in Atti di Convegno]
Briseghella, Bruno
abstract

Theoretical and experimental investigation (ambient vibration tests and permanent monitoring system) on the structural behavior of a curved cable-stayed bridge is presented in the paper. The quoted bridge was erected in the Commercial Harbor of Venice-Marghera, Italy, and opened to traffic on January 2007. The bridge is characterized by six curved spans, of which the main two of 105 m and 126 m are cablestayed, with the stays arranged on a single plane and connected to the centerline of the composite steel and concrete deck. Furthermore, the pre-stressed concrete pylon is single and inclined. As a consequence of the spatial structural arrangement, the dynamic behavior of the deck appears very complex both in bending and torsion. The peculiar architectural layout of the bridge added significant difficulties in both accurate structural analysis and assessment of "as built" behavior. Hence ambient vibration modal testing were carried out after erection and a detailed FE model was tuned and validated on such data. The special geometric layout of the bridge and its infrastructural role provided also a strong motivation for the installation of a permanent monitoring system. The paper describes the characteristics of the monitoring system, based on the use of the SOFO™ fiber optic sensor family and conceived for both static and dynamic monitoring. A number of considerations are carried out on the capability of the quoted monitoring system to assess in due time the presence of unexpected damage on the most critical zones of the bridge, namely inclined pylon and stay-cables. © 2010 Taylor & Francis Group, London.

2010 - Tensegrity bridge with prestressed deck [Relazione in Atti di Convegno]
Briseghella, B.; Fenu, L.; Huang, W.; Zordan, T.
abstract

In this paper, structural analysis and design of a tensegrity bridge with prestressed deck is introduced. As a matter of fact, cable pretension results in prestressing of the deck. Nonlinear geometric effects, key load cases, influence of main cable's rise and modal analysis of this type of structure is studied by finite element method. The structural behaviour of the tensegrity bridge appears to be suitable for a footbridge, although peculiar with respect to traditional footbridges. Some suggestions about structural design, material properties and structural behaviour are summarized.

2010 - The Fourth bridge over the Grand Canal in Venice: From idea to analysis and construction [Articolo su rivista]
Briseghella, Bruno
abstract

The new Fourth bridge over the Grand Canal, designed by the Spanish architect Santiago Calatrava; which was recently completed in Venice, is characterized by some original solutions in the Venetian panorama of traditional bridge design. Its stunning elevation, on a single 80 m span depressed "Vierendeel" arch with a span/rise ratio of 1/16, implies an extraordinary challenge for the foundation system in the muddy Venetian soil. The cross section of the bridge presents an open star-shaped layout with a central triangular steel box girder, thus implying a remarkable torsional deformability. The loose mechanical properties of the Venetian soil, together with the peculiar intrinsic structural and geometric characteristics of the footbridge, imposed a careful revision of the original design and some modifications aimed at achieving a globally stiffer structure without any alteration to its external outfit. The footbridge was pre-assembled and loaded prior to erection trying to simulate its final condition in terms of external restraints. In this phase a monitoring instrumentation was installed in order to better investigate its response. The erection design was conceived in order to take into account the extremely bounding conditions of the project area. A set of full-scale static tests of the structure was carried out before and after the erection to check the behaviour of the bridge.

2009 - Experiment on debonding in concrete-filled steel single tube columns subjected to eccentrically loading [Articolo su rivista]
Briseghella, Bruno
abstract

The confinement on concrete core by the steel tube is the main advantage of concrete-filled steel tubular (CFST) column under compression. However, the debonding of concrete from the steel tube common and it ruins the confinement effect. In this paper, the influence of debonding on the behavior of CFST stub columns subjected to eccentrically loading is investigated experimentally. The debonding was formed by inserting galvanized sheet in the steel tube before the concrete is filled and pulling them out after 5~6 hours. The test validates this method to form a debonding in specimens. The parameters in the tests include the debonding arc-length ratio and steel ratio. All the specimens failure in flexural mode, which indicates that the debonding has no influence on the failure mode, but the curvature of the debonding specimen is a little smaller than that of the normal specimen. The ultimate load capacity and the ductility of the specimens are significantly decreased with the increase of debonding arc-length ratio, which can be relieved by a larger steel ratio.

2009 - Nonlinear experimental response of non-conventional composite steel and concrete connection [Articolo su rivista]
Briseghella, Bruno
abstract

An experiment was carried out on a set of fullscale specimens of a non-conventional connection between a concrete column and a composite steel and concrete beam defined on the basis of a number of requirements. The proposed connection, conceived in the ambit of semirigid joints, is aimed at combining general ease of construction with a highly simplified assembly procedure with a satisfying transmission of hogging moment at supports in continuous beams. For this purpose, the traditional shear studs used at the interface between the steel beam and the upper concrete slab, are also employed at the ends of the steel profiles welded horizontally to the end plates. The test is aimed at investigating the hogging moment response of the connection under incremental loads until failure. © 2009 Higher Education Press and Springer-Verlag.

2007 - Attainment of a moment resisting structure through rehabilitation of a simply supported bridge [Relazione in Atti di Convegno]
Briseghella, B.; Sivicro, E.; Zordan, T.
abstract

Because of problems related to the management of the existing bridges patrimony due to new functional demands, the competent Authorities are asking for structures virtually free or with greatly reduced maintenance It is known that the temporal performance of structures does not depend just on the related performance of construction materials, but is deeply affected by their coupling, by the detailing, the static scheme (with the consequent state of stress and deformation) and finally by the boundary conditions (such as enviroivnental condition, volume and kind of traffic...). To overcome the problem of an increased volume of traffic together with the maintenance and management of bridges and flyovers. Road Authorities tend to accept major construction or retrofitting costs when an initially increased expense turns out to be economically favourable in a long period. In fact, any temporary interruption or limitation in traffic flow, caused by the presence of works is extremely expensive and considered as inappropriate by the community. IA8 (Integral abutment bridge) concept with the elimination of all bearings and expansion joints seems to adequately respond to the mentioned new functional demands with potentially very limited future maintenance problems By ilie way, lABs. must be carefully designed and built because of a number of possible inconveniences The paper will present a case study focusing on the refurbishment of a bridge responding to new functional demands such as greater user comfort and reduced future maintenance in order to obtain a kind of integral abutment bridge from a former simply supported structure with joints and bearings.

2007 - Attainment of an integral abutment bridge through the refurbishment of a simply supported structure [Articolo su rivista]
Zordan, T.; Briseghella, B.
abstract

Maintenance problems related to existing bridges represent a matter of major concern for road authorities that are recently accepting major construction or retrofitting costs when an initially increased expense would turn out to be economically favourable in a long period. Temporal performance of structures does not depend just on the related performance of construction materials, but is deeply affected by detailing, coupling, static scheme (with the consequent state of stress and deformation) and finally by the boundary conditions (such as environmental condition, volume and kind of traffic). Integral abutment bridge (IAB) concept, as explained in the following, with the elimination of all bearings and expansion joints seems to adequately respond to the mentioned functional demands with potentially limited maintenance problems during service life of the structure. After a concise description of the state of the art and possible inconvenience with IABs, the paper will present the transformation of a simply supported bridge into a IA structure on a total length of roughly 400 m using glued connections at piers and abutments.

2007 - Integral abutment bridge concept applied to the rehabilitation of a simply supported concrete structure [Articolo su rivista]
Briseghella, Bruno; Zordan,
abstract

A case study aiming to transform a simply supported pre-stressed concrete flyover into a frame structure throughout its full length, through refurbishment, is presented. Hogging moment resistance is achieved at the piers by the construction of a rigid transverse cast-in-place concrete diaphragm connected to the piers and to the beams of adjacent bays, in an attempt to fulfil the requirements of the integral abutment bridge (IAB) concept specified. All former bearings and expansion joints are eliminated resulting in an improved durability of the structure and greater comfort for the users. According to the IAB concept, hogging moment resistance is obtained by the flow of tensile forces through the concrete slab thanks to an increased ratio of reinforcement and the transmission of compressive forces directly through the concrete. Shear transmission is ensured by the installation of a convenient number of concrete-to-concrete shear studs on the webs of each of the beams forming the deck. Experimental tests were used to investigate the behaviour of shear studs. The possibility of making a simply supported deck continuous for a certain length depends on the soil-structure interaction and, consequently, on a wide number of parameters, varying from case to case, that will not be investigated in the present paper.

2006 - Advanced retrofitting techniques with hybrid use of carbon fibre and external post-tensioning: A case study [Relazione in Atti di Convegno]
Siviero, E.; Briseghella, B.; Zordan, T.
abstract

The fast growth of the European countries and the great increase of vehicle production have determined two immediate consequences on the organization of the viability. On one side, a road network suitable for high speed communication has been developed or in some cases created. On the other, within and around cities, urban and local traffic has dramatically increased often without any clear planning or strategy and without any care about the interference between roads and urban network. Traffic demand has implied, through the years, an increasing number of roads with different level of importance and the related consequence of limiting or planning their intersections. The most economical and feasible way to face the new demand for intersections deriving from the increased number of roads and the mentioned problems has been to create a great number of flyovers and tunnels, with a clear preference for the first ones because of limited cost and ease of construction. Especially during the fifties, the need for a fast and massive reconstruction determined the creation of economical and easily repeatable structures such as simply supported decks for the case of the bridges. In Italy, differently from other European countries, there has been no meaningful evolution within the field of flyovers and the main typologies have not substantially changed form the ones with simply supported pre-stressed concrete beams used for the reconstruction after the World War II. The mentioned solutions have proved to be quite unreliable with reference to durability because of scarce detailing and because of the presence of bearings and expansion joints, actually known as critical points for the activation of corrosion phenomena. The paper illustrated a case study for the retrofitting of existing bridges aiming to reduce the need for future maintenance.

Università degli studi di Modena e Reggio Emilia

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