|
PAOLA GAMBARELLI
Personale tecnico amministrativo Direzione Tecnica, Facility Management e Sostenibilità
|
Home |
Pubblicazioni
2018
- Human-induced vibrations of a curved cable-stayed footbridge
[Articolo su rivista]
Bassoli, Elisa; Gambarelli, Paola; Vincenzi, Loris
abstract
This paper investigates and compares the performances of two simulation models to predict the footbridge
response to vertical pedestrian dynamic actions. For this purpose, a rational procedure based on experimental
tests, identification, model-updating and simulation is addressed. The object of study is the Pasternak
footbridge, a curved cable-stayed footbridge prone to human-induced vibrations. The footbridge dynamic
behaviour is investigated thanks to an experimental campaign. Accelerations due to ambient vibrations are
recorded and the modal parameters of the structure are identified. The dynamic response to pedestrian
actions is investigated performing several experimental tests with different-sized groups of pedestrians. To
simulate the dynamic response to pedestrian actions, a Finite Element (FE) model of the footbridge is developed
and calibrated so that the numerical dynamic properties match the experimental ones. The structural
response to human loads is evaluated through two advanced simulation methods. The first one is based on
a periodic walking force and is employed to perform dynamic analyses with the FE model. In the second
one, a multi-harmonic force model, which considers the variability of the walking force, is adopted and the
dynamic response is evaluated via modal decomposition. Finally, numerical and experimental results are
compared with each other.
2017
- A proper infill sampling strategy for improving the speed performance of a Surrogate-Assisted Evolutionary Algorithm
[Articolo su rivista]
Vincenzi, Loris; Gambarelli, Paola
abstract
In the present paper, an improved Surrogate-Assisted Evolutionary Algorithm is proposed. It combines the Differential Evolution algorithm with a quadratic surrogate approximation and a proper infill sampling strategy to choose appropriate sample points. The selection of the new candidate points is arranged to enhance both the local accuracy and the global optimum search. A comparison between performances of different evolutionary algorithms is carried out by searching the global minimum of two benchmark functions, by solving a dynamic identification problem of a three floor frame and by calibrating the non-linear stress-crack opening relation for Fibre-Reinforced Concrete specimens starting from experimental data.
2015
- Dynamic analyses of a curved cable-stayed footbridge under human induced vibrations: numerical models and experimental tests
[Relazione in Atti di Convegno]
Bassoli, Elisa; Gambarelli, Paola; Simonini, Laura; Vincenzi, Loris
abstract
Nowadays, pedestrian bridges are increasingly lively and slender structures due to the devel-opment of improved structural materials and aesthetic requirements. As a result of this trend, contemporary footbridges are more and more prone to human-induced vertical and lateral vibrations that can compromise the comfort serviceability conditions. The goal of this paper is to characterize the dynamic behaviour of a curved cable-stayed footbridge subjected to pedestrian loads starting from experimental tests and numerical dynamic analyses. The dynamic behaviour of the footbridge is investigated thanks to an experimental campaign per-formed by means of an advanced MEMS-based SHM system. Accelerations due to ambient vibrations are recorded and the modal parameters of the structure are identified by means of a classic identification method. Then, to investigate the dynamic response of the footbridge subjected to pedestrian actions, a wide number of experimental tests were performed with dif-ferent-sized groups of pedestrians crossing the footbridge, running, free or synchronized walking with different pacing frequencies. Then, a finite element model of the footbridge is developed and calibrated so that the numerical dynamic predictions agree with the experi-mental modal properties. Then, to simulate dynamic loading conditions due to a single pedes-trian or a crowd of people crossing the footbridge, two mathematical models are examined. In the first approach both the non-calibrated and the updated FE model are adopted to evaluate the vertical dynamic response of the footbridge when subjected to pedestrian loads. Dynamic analyses are performed by simulating the pedestrian walking through a periodic load model representing the human-induced force as a deterministic force. The second approach is based on the solution of the equation of motion via modal decomposition, considering multi-harmonic forces and experimental mode shapes and frequencies. Finally, the accelerations obtained through the mathematical approaches are compared with the experimental results.
2015
- Dynamic monitoring of the Pasternak footbridge using MEMS-based sensing system
[Relazione in Atti di Convegno]
Bassoli, Elisa; Gambarelli, Paola; Simonini, Laura; Vincenzi, Loris; Savoia, Marco
abstract
The aim of this paper is to investigate the dynamic behaviour of a steel curved cable-stayed footbridge using an advanced MEMS-based Structural Health Monitoring system. Experimental campaigns were carried out in July and December to characterize the dynamic behaviour of the footbridge subjected to ambient vibrations and human-induced loading actions and to evaluate the effects of temperature shifts on structural modal properties. The monitoring system is composed of a controller and storage unit and several intelligent bus-connected sensing units that can record both the accelerations along two orthogonal axes and the temperature. The main features of this system are the transmission of data in digital form and its high signal-to-noise ratio in the low and medium-low frequency range. The structural dynamic properties are identified through the classic Enhanced Frequency Domain Decomposition (EFDD) method that is based on the diagonalization of the spectral density matrix. A preliminary FE model of the footbridge is built and the numerical results are compared with the experimental ones.
2014
- A surrogate-assisted evolutionary algorithm for dynamic structural identification
[Relazione in Atti di Convegno]
Gambarelli, Paola; Vincenzi, Loris
abstract
In the present paper, the performances of surrogate-assisted evolutionary algorithms for dynamic identification problems and damage detection are investigated. An improved algorithm is designed to limit the computational effort by introducing a proper infill sampling strategy in Differential Evolution (DE). The algorithm combines the robustness of DE with the computational efficiency due to a second-order surrogate approximation of the objective function. New individuals are selected trying to enhance both the accuracy in the region of the optimum predicted by the surrogate and the global exploration. The efficiency of the algorithm is tested by searching the global minimum of benchmark functions and by solving damage identifi-cation problems. Results are compared with those obtained adopting both the original DE algorithm and a previous proposal surrogate-based algorithm called DE-Q.