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MATTEO PELLICIARI

Ricercatore t.d. art. 24 c. 3 lett. A
Dipartimento di Ingegneria "Enzo Ferrari"
Docente a contratto
Dipartimento di Giurisprudenza

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Pubblicazioni

2023 - A strain energy function for large deformations of compressible elastomers [Articolo su rivista]
Pelliciari, M.; Sirotti, S.; Tarantino, A. M.
abstract

Elastomers are typically considered incompressible or slightly compressible. However, we present simple tension and bulk tests showing that, under large deformations, these materials can undergo significant volume changes. A review of the literature reveals the lack of an accurate hyperelastic model for finite volumetric deformations of elastomers. Therefore, we propose a new volumetric strain energy density (SED) that overcomes the limitations of the current models. The main advantages of the proposed SED are: (1) accurate description of the response of rubbers for both small and large volumetric deformations; (2) ability to reproduce diverse behaviors during volume shrinkage and expansion; (3) adaptability to other compressible materials, such as soft tissues, foams and hydrogels. Using the deviatoric- volumetric split of the strain energy, the proposed volumetric SED is combined with a suitable deviatoric part selected from the literature. The parameters of the combined SED are calibrated by fitting the model to the experimental data from simple tension and bulk tests. As a result, an accurate description of the response of elastomers under both shape and volume deformations is provided. The proposed SED can be implemented in numerical codes to capture the effects of volumetric deformations on the equilibrium solutions for various stress states.

2023 - Analytical pressure–deflection curves for the inflation of pre-stretched circular membranes [Articolo su rivista]
Sirotti, S.; Pelliciari, M.; Aloisio, A.; Tarantino, A. M.
abstract

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 - Theoretical and experimental analysis of the von Mises truss subjected to a horizontal load using a new hyperelastic model with hardening [Articolo su rivista]
Pelliciari, Matteo; Falope, FEDERICO OYEDEJI; Lanzoni, Luca; Tarantino, Angelo Marcello
abstract

The von Mises truss has been widely studied in the literature because of its numerous applications in multistable and morphing structures. The static equilibrium of this structure was typically addresses by considering only geometric nonlinearities. However, Falope et al. (2021) presented an entirely nonlinear solution in finite elasticity and demonstrated that material nonlinearities play an important role in the prediction of both snap-through and Euler buckling. In such work, the von Mises truss was subjected to a vertical load and thus the system was symmetric and the deformations were relatively small. The present contribution extends the investigation to the case of a horizontal load, which is much more complex due to asymmetry and very large deformations. Since most rubbers employed in technological applications exhibit hardening under large stretches, we propose a new hyperelastic model capable of reproducing this behavior. The advantage of such model compared to the ones available in the literature is that the equilibrium solution maintains a straightforward mathematical form, even when considering compressibility of the material. In addition, in this work we present a new formulation in nonlinear elasticity to predict Euler buckling. The formulation takes into account shear deformation. The analytical prediction agrees well with both finite element (FE) and experimental results, thus demonstrating the accuracy of the proposed model.

2022 - A Continuum Model for Circular Graphene Membranes Under Uniform Lateral Pressure [Articolo su rivista]
Pelliciari, M; Tarantino, Am
abstract

Despite the numerous applications of pressurized graphene membranes in new technologies, there is still a lack of accurate mechanical models. In this work we develop a continuum model for circular graphene membranes subjected to uniform lateral pressure. We adopt a semi-inverse method by defining a simplified kinematics of deformation and we describe the material behavior with a stored energy function that takes into account both nonlinearity and anisotropy of graphene. An expression of the applied pressure as a function of the deflection of the membrane is obtained from an approximate solution of the equilibrium. The simplifying hypotheses of the analytical model are verified by a finite element (FE) analysis in nonlinear elasticity. In addition, a numerical solution of the differential equilibrium equations of the exact theory is presented. The pressure-deflection response from FE and numerical solutions agree well with the prediction of the analytical formula, demonstrating its accuracy. The analytical solution is then employed for the response of a two-layered composite membrane made of graphene deposited onto a soft substrate. This application is of great interest since new nanotechnologies make use of layered nanocomposites. Differently from our entirely nonlinear approach, most continuum models in the literature are based on the assumption of linear elastic material, which is suitable only when deformations are small. The present work gives a comprehensive description of the mechanics of pressurized graphene membranes.

2022 - A continuum model for graphene in nonlinear elasticity and its green applications [Abstract in Atti di Convegno]
Pelliciari, Matteo; Tarantino, Angelo Marcello; Lanzoni, Luca
abstract

2022 - Analytical and experimental study of snap-through instability in truss structures [Abstract in Atti di Convegno]
Pelliciari, Matteo; Falope, FEDERICO OYEDEJI; Lanzoni, Luca; Tarantino, Angelo Marcello
abstract

Abstract

2022 - Analytical, numerical and experimental study of the finite inflation of circular membranes [Articolo su rivista]
Pelliciari, M.; Sirotti, S.; Aloisio, A.; Tarantino, A. M.
abstract

In the present work we derive an analytical expression for the pressure–deflection curve of circular membranes subjected to inflation. This problem has been studied mostly from a numerical point of view and there is still a lack of accurate closed-form solutions in nonlinear elasticity. The analytical formulation is developed with a semi-inverse method by setting a priori the kinematics of deformation of the membrane. A compressible Mooney–Rivlin material model is considered and a pressure–deflection relation is derived from the equilibrium. The kinematics is approximated and therefore the obtained solution is not exact. Consequently, the formulation is adjusted by introducing an additional polynomial function in the pressure–deflection equation. The polynomial is calibrated by fitting numerical solutions of the exact system of differential equilibrium equations. The calibration is done over a wide range of constitutive parameters that covers the response of all rubber materials for technological applications. As a result, a definitive and accurate expression of the applied pressure as a function of the deflection of the membrane is obtained. The formula is validated with finite element (FE) simulations and compared with other solutions available in the literature. The comparison shows that the present model is more accurate. In addition, unlike the other models, it can be applied to compressible materials. Experimental uniaxial and bulge tests are carried out on rubber materials and the model proposed is used to characterize the Mooney–Rivlin constitutive parameters. Since the pressure–deflection formula is accurate and easy-to-use, it is an innovative tool in engineering applications of inflated membranes.

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 - Optimization of the structural coupling between RC frames, CLT shear walls and asymmetric friction connections [Articolo su rivista]
Aloisio, A.; Pelliciari, M.; Sirotti, S.; Boggian, F.; Tomasi, R.
abstract

This paper focuses on the optimum design of the e-CLT technology. The e-CLT technology consists in adding cross laminated timber (CLT) walls to an existing reinforced concrete (RC) infilled frame via asymmetric friction connection (AFC). The authors carried out quasi-static and nonlinear dynamic analyses. The RC frame is modeled in OpenSees by fiber-section-based elements with force-based formulation. The contribution of the infill is simulated using a degrading data-driven Bouc–Wen model with a slip-lock element while the AFC is modelled with a modified Coulomb model. Different types of infill, aspect ratio, scaling, and member size are considered. The benefits of using e-CLT technology are discussed and the ranges of optimum performance of the AFC are estimated. A comparison of the performance of traditional infills with the e-CLT system is presented. The authors provide optimum intervals of the ratio between slip force and in-plane stiffness of the CLT panel, following energy and displacement-based criteria. The seismic displacement demand under various seismic scenario is investigated. Correlations between the RC characteristics and the optimum design ratios bestow possible criteria for the design of the AFC.

2022 - Size effect in single layer graphene sheets and transition from molecular mechanics to continuum theory [Articolo su rivista]
Pelliciari, M.; Pasca, D. P.; Aloisio, A.; Tarantino, A. M.
abstract

The size-dependent mechanical response of graphene is investigated with an entirely nonlinear molecular mechanics approach. Finite element (FE) simulations under uniaxial and equibiaxial tensile loads are carried out on graphene sheets with increasing size. It is found that the response of graphene remains unchanged after a threshold size. Furthermore, anisotropy is observed for large deformations and a negative Poisson's ratio is found after a critical strain for the zigzag uniaxial load case. The threshold size defines the transition to the continuum theory, which is developed as a membrane model in the fully nonlinear context of finite elasticity. The constitutive parameters of the model are calibrated by fitting the results of the FE simulations. The proposed model represents the basis for accurate predictions of the response of graphene subjected to large in-plane deformations. Nonlinear laws for the size-dependent elastic properties of graphene are derived. These laws can be used in linear elasticity-based models to take into account for material nonlinearity, anisotropy and size effect. Finally, a sensitivity analysis of the molecular mechanics model to the parameters of the interatomic potentials is carried out. The discussion of the results gives insights into the influence of each parameter and useful remarks for the molecular mechanics modeling of graphene.

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 nonlinear molecular mechanics model for graphene subjected to large in-plane deformations [Articolo su rivista]
Pelliciari, M.; Tarantino, A. M.
abstract

In this paper we present a fully nonlinear stick-and-spring model for graphene subjected to in-plane deformations. The constitutive behaviors of sticks and springs are defined, respectively, by the modified Morse potential and a nonlinear bond angle potential. The equilibrium equations of the representative cell are written considering large displacements of the nodes (atoms) and the stability of the solutions is assessed using an energy criterion. The solutions for the uniaxial load cases along armchair and zigzag directions show that graphene is isotropic for small deformations, while it exhibits anisotropy when subjected to large deformations. Moreover, graphene shows a negative Poisson's ratio after a critical value of deformation. In the case of equibiaxial load, multiple solutions of the equilibrium are found and graphene can experience asymmetric deformations despite the symmetry of the external loads. The nonlinear formulation of the equilibrium is then linearized by introducing the hypothesis of small displacements. The expressions of Young's modulus and Poisson's ratio are derived.

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 - Dispositivo per l'isolamento di apparecchiature industriali, strutture e infrastrutture civili basato su moduli reticolari a traliccio [Brevetto]
Falope, FEDERICO OYEDEJI; Lanzoni, Luca; Pelliciari, Matteo; Tarantino, Angelo Marcello; Salardi, Enrico
abstract

2021 - Equilibrium and Stability of Anisotropic Hyperelastic Graphene Membranes [Articolo su rivista]
Pelliciari, M.; Tarantino, A. M.
abstract

The lack of experimental investigations on graphene fostered researchers to focus on its mechanical modeling. Being graphene a one-atom-thick sheet, many authors developed continuum membrane models to analyze its mechanical behavior. However, an entirely nonlinear approach in finite elasticity has not been presented so far. In this work, the equilibrium problem of anisotropic hyperelastic graphene membranes is addressed. Strain and stress measures are expressed under the hypothesis of homogeneous deformations and the boundary-value problem is formulated for a graphene membrane subjected to biaxial loads. The stability of the equilibrium configurations is assessed through an energy criterion. Explicit relations between stretches and stresses of the membrane are derived for the cases of uniaxial and equibiaxial loads. Unexpectedly, bifurcation and multiple equilibrium solutions are found when graphene is subjected to equibiaxial loads. A linearization of the finite theory is presented and the expressions of Young’s modulus and Poisson’s ratio of graphene are derived. The formulation proposed in this work may be the basis for accurate investigations of the mechanics of graphene subjected to large deformations.

2021 - Snap-through and Eulerian buckling of the bi-stable von Mises truss in nonlinear elasticity: A theoretical, numerical and experimental investigation [Articolo su rivista]
Falope, F. O.; Pelliciari, M.; Lanzoni, L.; Tarantino, A. M.
abstract

In this paper, the equilibrium and stability of the von Mises truss subjected to a vertical load is analyzed from theoretical, numerical and experimental points of view. The bars of the truss are composed of a rubber material, so that large deformations can be observed. The analytical model of the truss is developed in the fully nonlinear context of finite elasticity and the constitutive behavior of the rubber is modeled using a Mooney–Rivlin law. The constitutive parameters are identified by means of a genetic algorithm that fits experimental data from uniaxial tests on rubber specimens. The numerical analysis is performed through a finite element (FE) model. Differently from the analytical and FE simulations that can be found in the literature, the models presented in this work are entirely developed in three-dimensional finite elasticity. Experiments are conducted with a device that allows the rubber specimens to undergo large axial deformations. For the first time, snap-through is observed experimentally on rubber materials, showing good agreement with both theoretical and numerical results. Further insights on Eulerian buckling of the rubber specimens and its interaction with the snap-through are given. A simple formulation to determine the critical load of the truss is presented and its accuracy is validated through experimental observation. Comparisons with a linear elasticity based approach demonstrate that an accurate prediction of snap-through and Eulerian buckling requires nonlinear formulations, such as the ones proposed in this work.

2021 - Snap-through and Eulerian buckling of the von Mises truss [Relazione in Atti di Convegno]
Pelliciari, Matteo; Falope, FEDERICO OYEDEJI; Lanzoni, Luca; Tarantino, Angelo Marcello
abstract

2021 - Snap-through of a bi-stable truss in finite elasticity [Relazione in Atti di Convegno]
Pelliciari, M.; Falope, F. O.; Lanzoni, L.; Tarantino, A. M.
abstract

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 psychological impact of COVID-19 and restrictive measures in the world [Articolo su rivista]
Passavanti, M.; Argentieri, A.; Barbieri, D. M.; Lou, B.; Wijayaratna, K.; Foroutan Mirhosseini, A. S.; Wang, F.; Naseri, S.; Qamhia, I.; Tangeras, M.; Pelliciari, M.; Ho, C. -H.
abstract

Background: In a short time, the COVID-19 pandemic turned into a global emergency. The fear of becoming infected and the lockdown measures have drastically changed people's daily routine. The aim of this study is to establish the psychological impact that the COVID-19 pandemic is entailing, particularly with regards to levels of stress, anxiety and depression, and to the risks of developing Post-Traumatic Stress Disorder (PTSD). Methods: The study, carried out with a sample of 1612 subjects distributed in seven countries (Australia, China, Ecuador, Iran, Italy, Norway and the United States), allowed us to collect information about the psychological impact of COVID-19. Results: The findings of this study show that the levels of stress, depression and anxiety, as well as the risks of PTSD, are higher than average in over half of the considered sample. The severity of these disorders significantly depends on gender, type of outdoor activities, characteristics of their homes, eventual presence of infected acquaintances, time dedicated to looking for related information (in the news and social networks), type of source information and, in part, to the level of education and income. Conclusions: We conclude that COVID-19 has a very strong psychological impact on the global population. This appears to be linked to the coping strategies adopted, level of mindful awareness, socio-demographic variables, people's habits and the way individuals use means of communication and information.

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 - Dispositivo smorzatore assiale ad elastomeri [Brevetto]
Falope, FEDERICO OYEDEJI; Pelliciari, Matteo; Lanzoni, Luca; Tarantino, Angelo Marcello; Salardi, Enrico
abstract

2020 - Equilibrium Paths for von Mises Trusses in Finite Elasticity [Articolo su rivista]
Pelliciari, M.; Tarantino, A. M.
abstract

This paper deals with the equilibrium problem of von Mises trusses in nonlinear elasticity. A general loading condition is considered and the rods are regarded as hyperelastic bodies composed of a homogeneous isotropic material. Under the hypothesis of homogeneous deformations, the finite displacement fields and deformation gradients are derived. Consequently, the Piola-Kirchhoff and Cauchy stress tensors are computed by formulating the boundary-value problem. The equilibrium in the deformed configuration is then written and the stability of the equilibrium paths is assessed through the energy criterion. An application assuming a compressible Mooney-Rivlin material is performed. The equilibrium solutions for the case of vertical load present primary and secondary branches. Although, the stability analysis reveals that the only form of instability is the snap-through phenomenon. Finally, the finite theory is linearized by introducing the hypotheses of small displacement and strain fields. By doing so, the classical solution of the two-bar truss in linear elasticity is recovered.

2020 - Equilibrium of the von mises truss in nonlinear elasticity [Abstract in Atti di Convegno]
Pelliciari, M.; Tarantino, A. M.
abstract

In this contribution, a nonlinear formulation of the equilibrium problem of the von Mises truss (or two-bar truss) is presented. The bars are regarded as three-dimensional bodies composed of a homogeneous and isotropic material. The displacement fields are written under the assumption of homogeneous deformations and, consequently, the boundary-value problem is formulated. The relations governing the equilibrium of each body are thus derived and the global equilibrium of the von Mises truss under a general loading condition is written. The stability of the equilibrium solutions is assessed through the energy criterion. An application considering a compressible Mooney-Rivlin material shows interesting post-critical behaviors, involving snap-through and multiple branches.

2020 - Equilibrium paths of a three-bar truss in finite elasticity with an application to graphene [Articolo su rivista]
Pelliciari, M.; Tarantino, A. M.
abstract

This paper presents the formulation of the equilibrium problem of a three-bar truss in the nonlinear context of finite elasticity. The bars are composed of a homogeneous, isotropic, and compressible hyperelastic material. The equilibrium equations in the deformed configuration are derived under the assumption of homogeneous deformations and the stability of the solutions is assessed through the energy criterion. The general formulation is then specialized for a compressible Mooney–Rivlin material. The results for both vertical and horizontal load cases show unexpected post-critical behaviors involving several branches, stable asymmetrical configurations, bifurcation, and snap-through. The three-bar truss studied here is not only a benchmark test for the numerical analysis of nonlinear truss structures, but also a representative system for the unit cell of the graphene hexagonal lattice. Therefore, an application to graphene is performed by simulating the covalent bonds between carbon atoms as the bars of the truss, characterized by the modified Morse potential. The results provide insights on the internal mechanisms that take place when graphene undergoes large in-plane deformations, whose influence should be considered when developing molecular mechanics and continuum models in nonlinear elasticity.

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.

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 - degrading Bouc-Wen model parametrers identification under cyclic load [Articolo su rivista]
G. C., Marano; Pelliciari, Matteo
abstract

The Bouc–Wen model of hysteresis is used in structural engineering to describe a wide range of nonlinear hysteretic systems, as consequence of its capability to produce a variety of hysteretic patterns. This research 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 and retrofitted reinforced concrete bridge pier specimens (in a 1:6 scale of a real bridge pier) tested physically in a laboratory are considered in this paper. 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 and 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; reduction of the number of parameters. The latter innovation is much 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 fitting the experimental ones and are reliable in terms of manageability, stability, and computational time.