EGIS Industries

Montreuil, France

EGIS Industries

Montreuil, France
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Kumar P.,Indian Institute of Technology Roorkee | Kumar A.,Indian Institute of Technology Roorkee | Racic V.,University of Sheffield | Racic V.,Polytechnic of Milan | Erlicher S.,EGIS Industries
Mechanical Systems and Signal Processing | Year: 2018

This paper proposes a model of a self-sustained oscillator which can generate reliably the vertical contact force between the feet of a healthy pedestrian and the supporting flat rigid surface. The model is motivated by the self-sustained nature of the walking process, i.e. a pedestrian generates the required inner energy to sustain its repetitive body motion. The derived model is a fusion of the well-known Rayleigh, Van der Pol and Duffing oscillators. Some additional nonlinear terms are added to produce both the odd and even harmonics observed in the experimentally measured force data. The model parameters were derived from force records due to twelve pedestrians walking on an instrumented treadmill at ten speeds using a linear least square technique. The stability analysis was performed using the energy balance method and perturbation method. The results obtained from the model show a good agreement with the experimental results. © 2017 Elsevier Ltd

Huguet M.,EGIS Industries | Huguet M.,École Centrale Nantes | Erlicher S.,EGIS Industries | Kotronis P.,École Centrale Nantes | Voldoire F.,Électricité de France
Engineering Fracture Mechanics | Year: 2017

The paper proposes a novel stress resultant nonlinear constitutive model for Reinforced Concrete (RC) panels adapted to cyclic loadings. An analytical multi-scale analysis is applied by taking a concrete strut with embedded steel reinforcement between two consecutive cracks as representative volume element. Some suitable assumptions are adopted in order to incorporate the most important nonlinear phenomena characterizing reinforced concrete behavior: concrete damage, concrete cracking, bond-slip stress (at the origin of the tension stiffening effect) and steel yielding. The model is validated by comparison with experimental data concerning tension and tension-compression uniaxial tests on RC beams and a cyclic (non-reversing) shear test on an RC wall. © 2017 Elsevier Ltd

Kumar P.,Indian Institute of Technology Roorkee | Kumar A.,Indian Institute of Technology Roorkee | Erlicher S.,EGIS Industries
International Journal of Structural Stability and Dynamics | Year: 2017

This study proposes a single degree of freedom nonlinear oscillator to model the lateral movement of the body center of mass of a pedestrian walking on a flat rigid surface. Experimentally recorded ground reaction force of a dozen of pedestrians in the lateral direction is used to develop the model. In detail, the hardening and softening effects are observed in the stiffness curve as well as higher odd harmonics are present in the frequency spectrum of the lateral force signals. The proposed oscillator is a modification of the Rayleigh and the Van der Pol oscillators with additional nonlinear softening and hardening terms. To obtain an approximation of the limit cycle of the oscillator and its stability, two methods are studied: the energy balance method and the Lindstedt–Poincare perturbation technique. The experimental force signals of pedestrians at four different walking speeds are used for the identification of the values of the model parameters. The results obtained from the proposed model show a good agreement with the experimental ones. © 2018 World Scientific Publishing Company

Kumar P.,Indian Institute of Technology Roorkee | Kumar A.,Indian Institute of Technology Roorkee | Erlicher S.,EGIS Industries
Physica D: Nonlinear Phenomena | Year: 2017

The paper proposes a single degree of freedom oscillator in order to accurately represent the lateral force acting on a rigid floor due to human walking. As a pedestrian produces itself the energy required to maintain its motion, it can be modelled as a self-sustained oscillator that is able to produce: (i) self-sustained motion; (ii) a lateral periodic force signal; and (iii) a stable limit cycle. The proposed oscillator is a modification of hybrid Van der Pol-Duffing-Rayleigh oscillator, by introducing an additional nonlinear hardening term. Stability analysis of the proposed oscillator has been performed by using the energy balance method and the Lindstedt-Poincare perturbation technique. Model parameters were identified from the experimental force signals of ten pedestrians using the least squares identification technique. The experimental and the model generated lateral forces show a good agreement. © 2017 Elsevier B.V.

Kabalan B.,University Paris Est Creteil | Argoul P.,University Paris Est Creteil | Jebrane A.,Cadi Ayyad University | Cumunel G.,University Paris Est Creteil | Erlicher S.,EGIS Industries
Annals of Solid and Structural Mechanics | Year: 2016

One of the main objectives of crowd modeling is to optimize evacuation and improve the design of pedestrian facilities. In this work, a sensitivity analysis is performed to study the effect of the parameters of a 2D discrete crowd movement model on the nature of pedestrian’s collision and on evacuation times. After presenting the proposed model in its full version (three degrees of freedom for each individual), a pedestrian–pedestrian collision is considered. We identified the parameters that govern this type of collision and studied their effects on it. Then an evacuation experiment of a facility with a bottleneck exit is introduced and its configuration is used for numerical simulations. It is shown that without introducing a social repulsive force, the obtained flow rate values are much higher than the experimental ones. For this reason, we introduced the social force as defined by Helbing and performed a parametric study to find the set of optimized values of this force’s parameters that enables us to achieve simulation results close to the experimental ones. Using the values of the parameters obtained from the parametric study, the evacuation simulations give flow rate values that are closer to the experimental ones. The same optimized model is then used to find the density in front and inside the bottleneck and to reproduce the lane formation phenomenon as was observed in the experiment. Finally, the obtained results are analyzed and discussed. © 2016 Springer-Verlag Berlin Heidelberg

Pecol P.,ParisTech National School of Bridges and Roads | Dal Pont S.,University Paris Est Creteil | Erlicher S.,EGIS Industries | Argoul P.,ParisTech National School of Bridges and Roads
Annals of Solid and Structural Mechanics | Year: 2011

The aim of this paper is to develop on discrete models that reproduce the behavior of a crowd of people in several emergency evacuation situations. The first step in this study is to determine how to treat contacts between pedestrians. For that, three already existing discrete approaches, one smooth and two non-smooth, originally proposed to simulate the collisions of granular assemblies, are first analyzed both from the theoretical and the numerical point of view. The solving algorithms are presented and the numerical formulation of the two non-smooth approaches is compared to standard plasticity in order to point out the common theoretical framework. The next step is to adapt these discrete approaches to represent pedestrians. The key point is to introduce a "willingness" for each particle through a specific desired velocity. These adapted discrete approaches are able to handle local interactions, like pedestrian-pedestrian or pedestrian-obstacle contacts, in order to reproduce the global dynamic of pedestrian traffic. Finally, results of several simulations in emergency configurations are presented as well as compared to real exercise ones. © 2011 Springer-Verlag.

Erlicher S.,EGIS Industries | Trovato A.,University Paris Est Creteil | Trovato A.,University of Calabria | Argoul P.,University Paris Est Creteil
Mechanical Systems and Signal Processing | Year: 2013

A single degree of freedom self-sustained oscillator is proposed in order to model the lateral oscillations of a pedestrian walking on a periodically moving floor and particularly on a shaking table. In a previous work, the authors have shown that a suitable form for the restoring force of such an oscillator corresponds with a modified hybrid Van der Pol/Rayleigh (MHVR) model, whose associated parameters have been identified in the autonomous (rigid floor) case for a group of twelve pedestrians. The MHVR oscillator is analyzed here for the non-autonomous case, where the moving floor is subjected to a harmonic excitation. It has been experimentally proven that in this case the pedestrian may change his (her) natural walking frequency and synchronize with the floor oscillation frequency: one says that the so-called "frequency entrainment" occurs. This means that, under certain conditions, the response frequency switches from the natural value to that of the external excitation. This paper discusses the steady "entrained" response of the MHVR model subjected to a harmonic excitation, in terms of response amplitude curves obtained using the Harmonic Balance Method. Experimental results available in the literature and involving pedestrians walking on a shaking table are compared with the model predictions for illustrative purposes. © 2013 Elsevier Ltd.

Ceravolo R.,Polytechnic University of Turin | Erlicher S.,EGIS Industries | Zanotti Fragonara L.,Polytechnic University of Turin
Journal of Sound and Vibration | Year: 2013

When subjected to events such as earthquakes, engineering structures typically exhibit a nonlinear and hysteretic behaviour with stiffness and strength degradations. Though a reliable evaluation of safety conditions should take into account the nonlinear dynamic and evolutionary nature of the structural response, the experimental identification of a nonlinear behaviour under dynamic and seismic loading is, to date, an open problem. The present research aims at evaluating the potential of different restoring force models for simulating the seismic response of hysteretic structural systems, with special emphasis on the two main problems encountered when applying this approach to full-scale structures under intense excitation: (a) a markedly time-dependent behaviour; (b) need to compare among different restoring force models, either expressed in a parametric or polynomial form. In particular, polynomial models will be formulated both in terms of restoring force and its derivative, in order to present a comprehensive discussion of different strategies. The nonlinear identification technique employed in this paper is required to account for a time-dependent behaviour. In fact, in presence of degradation or any other time-varying characteristics, instantaneous identification certainly constitutes an enhancement of the classical restoring force based approach, and may as well provide checks on the consistency of the assumed models. © 2013 Elsevier Ltd.

Trovato A.,University of Calabria | Kumar A.,Indian Institute of Technology Roorkee | Erlicher S.,EGIS Industries
Annals of Solid and Structural Mechanics | Year: 2014

In this article, the entrained response of the modified hybrid Van der Pol/Rayleigh (MHVR) oscillator undergoing a periodic excitation is analyzed. Based on a large experimental database, this self-sustained oscillator was originally proposed by the authors to model the lateral ground force of a pedestrian walking on a rigid floor. In this situation, there is no external excitation on the oscillator (autonomous regime). In a successive development, the authors used the MHVR oscillator in the non-autonomous regime to model the lateral oscillations of a pedestrian walking on a periodically moving floor. In the same work, the MHVR oscillator was analyzed in terms of amplitude of the entrained response, i.e. a solution having constant amplitude and the same frequency as the one of the given periodic excitation. The main goal of the present paper is the stability analysis of entrained responses. Some theoretical results are first discussed. Then, these theoretical notions are applied to the pedestrian modelling problem: the conditions allowing stability of the solution are used to compute the percentage of pedestrians of a given population that can synchronize their walk with a given periodic floor motion. Finally, these model predictions are compared with experimental results concerning pedestrians walking on a periodically moving floor. © 2014, Springer-Verlag Berlin Heidelberg.

Huguet M.,École Centrale Nantes | Voldoire F.,Électricité de France | Kotronis P.,École Centrale Nantes | Erlicher S.,EGIS Industries
11th World Congress on Computational Mechanics, WCCM 2014, 5th European Conference on Computational Mechanics, ECCM 2014 and 6th European Conference on Computational Fluid Dynamics, ECFD 2014 | Year: 2014

A new nonlinear stress resultant global constitutive model for RC panels is presented. Concrete damage, concrete stress transfer at cracks and bond-slip stress are the main nonlinear effects identified at the local scale that constitute the basis for the construction of the stress resultant global model through an analytical homogenization technique. The closed form solution is obtained using general functions for the previous phenomena.

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