A 3D beam element analysis for R/C structural walls

To analyse the real 3D functioning of a structure under seismic loading the dialogue between tests and numerical simulations is needed. Within the framework of the TMR-ICONS research program, dynamic and cyclic tests on U-shaped shear walls have been performed at CEA Saclay and JRC Ispra respectively. More recently, for the French program ìCAMUS 2000î, shaking table tests have been performed on reinforced concrete structural walls. In order to simulate these tests, 3D multi-fiber beam elements are used. Comparison with the experimental results shows the well matching and the limitations of the approach

Une nouvelle loi constitutive pour la description du comportement cyclique des matériaux quasi-fragiles : effet unilatéral régularisé et effets hystérétiques

Une nouvelle loi de comportement visant à étudier le comportement du béton sous chargement cyclique est proposée. La formulation de la loi repose en partie sur une approche par expérimentation numérique à l'aide d'un modèle de type lattice. Ainsi, une prise en compte de l'effet unilatéral régularisé est proposée afin de décrire le phénomène de refermeture progressif des fissures. La loi de comportement développée a été validée à l'échelle de la structure sur le cas d'un voile en béton armé sous chargement cyclique

Numerical modelling for earthquake engineering: the case of lightly RC structural walls

Different types of numerical models exist to describe the non‐linear behaviour of reinforced concrete structures. Based on the level of discretization they are often classified as refined or simplified ones. The efficiency of two simplified models using beam elements and damage mechanics in describing the global and local behaviour of lightly reinforced concrete structural walls subjected to seismic loadings is investigated in this paper. The first model uses an implicit and the second an explicit numerical scheme. For each case, the results of the CAMUS 2000 experimental programme are used to validate the approaches

Experimental study of corrosion-induced degradation of reinforced concrete elements

Corrosion of steel reinforcement is the main cause of damage for reinforced concrete structures. Iron oxides produced during the corrosion process can induce concrete cracking, loss of adhesion at the steel-concrete interface, loss of reinforcing bar cross-section and even spalling of the concrete cover. In the presented research, the durability problems related to the corrosion of the reinforcement are investigated by combining experimental and numerical studies. However, this paper particularly focuses on the experimental methodology used for the time evolution of damages (steel corrosion products formation and crack patterns) induced by the accelerated corrosion test. The accelerated corrosion tests were carried out by applying a constant current between reinforcement used as an anode and a counter electrode. To control the corrosion process, electrochemical parameters (such as free corrosion potential, polarization resistance, electrical concrete resistance) were measured. The purpose of this paper is to determine the width and length of the cracks and their orientation according to the current density and time

Methodology for updating magnitudes assigned to historical earthquakes: application to the La Tour-du-Pin 1889 earthquake

International audienc

A Stochastic Multi-scale Approach for Numerical Modeling of Complex Materials - Application to Uniaxial Cyclic Response of Concrete

In complex materials, numerous intertwined phenomena underlie the overall response at macroscale. These phenomena can pertain to different engineering fields (mechanical , chemical, electrical), occur at different scales, can appear as uncertain, and are nonlinear. Interacting with complex materials thus calls for developing nonlinear computational approaches where multi-scale techniques that grasp key phenomena at the relevant scale need to be mingled with stochastic methods accounting for uncertainties. In this chapter, we develop such a computational approach for modeling the mechanical response of a representative volume of concrete in uniaxial cyclic loading. A mesoscale is defined such that it represents an equivalent heterogeneous medium: nonlinear local response is modeled in the framework of Thermodynamics with Internal Variables; spatial variability of the local response is represented by correlated random vector fields generated with the Spectral Representation Method. Macroscale response is recovered through standard ho-mogenization procedure from Micromechanics and shows salient features of the uniaxial cyclic response of concrete that are not explicitly modeled at mesoscale.Comment: Computational Methods for Solids and Fluids, 41, Springer International Publishing, pp.123-160, 2016, Computational Methods in Applied Sciences, 978-3-319-27994-

Contribution à l'identification de l'amortissement (approches expérimentales et numériques)

Il est difficile de quantifier les dissipations d'énergie se produisant dans les ouvrages lors d'un séisme de manière réaliste, en particulier dans le cas de structures en béton armé. Ceci s'explique par la diversité des sources de dissipations. Classiquement, elles sont introduites dans la modélisation des structures sous la forme d'un amortissement global peu physique. Le problème qui se pose est de savoir comment prendre en compte l'amortissement de manière plus physique. Ces travaux visent à apporter des éléments de réponse à cette problématique. Pour cela, deux objectifs ont été poursuivis : le premier consiste à qualifier et quantifier expérimentalement les sources d'amortissement dues au béton, le second vise à développer une méthode de calcul, peu couteuse et permettant de modéliser le comportement global mais aussi l'amortissement de manière réaliste. Une campagne d'essais de flexion 3 points alternée a été réalisée afin de quantifier les mécanismes contribuant à l'amortissement. Cette campagne est effectuée sur des poutres saines mais également sur des poutres pré-endommagées. L'analyse des expériences a permis d identifier différentes grandeurs physiques influençant l amortissement. Cette campagne a été modélisée à l'aide de trois lois de comportements, une loi s'est révélée pertinente. La loi de comportement ainsi identifiée a permis de développer une modélisation simplifiée, en vue d'études probabilistes. Cette dernière est fondée sur une loi de comportement simple couplée à une actualisation de l'amortissement visqueux. Trois actualisations de l'amortissement ont été développées et confrontées à une campagne d'essais sismiques mono axiaux sur un poteau.It is hard to determine the energy dissipation that occurs during an earthquake, especially where reinforced concrete structures are concerned. The reason for this is the many different causes of energy dissipation, these dissipations typically creep into the essential pattern of the structures as a uniform, slight damping, and which is heavily quantify. The challenge is therefore to ascertain how to carry out damping in a way that relies more on the laws of physics themselves. This study aims at bringing some clarifications to this problem. In order to achieve this, two objectives were targeted during the case study: the first consisted in experimentally qualifying and quantifying the sources of damping in concrete, the second aims at developing a method which model both the overall behaviour and the damping in a realistic way with low computational costs. Reverse 3-point bending tests were carried out to determine and quantify the mechanisms responsible for damping. The tests were carried out on sound beams, and also on pre-damaged beams. It was possible to relate the damping to the damage, the intensity of the load and the erosion of the crack surfaces. These tests were modeled using three physical constitutive laws, one proved to be relevant. The behaviour law thus identified allowed us to develop a simplified model to be used during probabilistic assessments. This model is based on a simple constitutive law, coupled with the updating of viscous damping. It is carried out according to the evolutions of the mechanical properties of the structure and the load. Three updates of the damping were developed and subjected to a serie of mono axial seismic tests on a column.CACHAN-ENS (940162301) / SudocSudocFranceF

Simplified modelling accounting for shear and torsion

International audienc