Numerical fracture analysis coupling thermo-hygro mechanical and viscoelastic behaviour

International audienc

Analyse fiabiliste du taux de restitution d'énergie en milieux viscoélastiques orthotropes

Un modèle mécano-fiabiliste est développé pour l'analyse de la fissuration dans un milieu viscoélastique orthotrope en mode mixte de chargement. La formulation analytique est introduite par l'intégrale M généralisée au comportement viscoélastique et résolue par une approche incrémentale issue du théorème des travaux virtuels. Les incertitudes sur les propriétés du matériau sont prises en compte par des variables aléatoires afin de calculer la probabilité de propagation de fissure. L'application numérique est effectuée sur un modèle éléments finis d'une plaque fissurée en matériau composite

Fissuration des rondelles de Sapin blanc du Massif Central suite au séchage naturel

National audienc

On Numerical Evaluation of Mixed Mode Crack Propagation Coupling Mechanical and Thermal Loads in Wood Material

The mixed-mode crack growth coupling mechanical and thermal loads in wood material is investigated in this numerical work. The analytical formulation the crack driving force, namely the energy release rate, is introduced by T-integral that takes into account mixed mode fracture, thermal process in orthotropic material and pressure applied on the crack lips. This new formulation is based on Nother’s theorem and the definition of the strain energy density according to Lagrangian’s and Eulerian’s configurations. Moreover, this analytical formulation is implemented in finite element software Cast3m. First of all, several numerical examples, dealing with isotropic material, are provided to illustrate the accuracy of the FEM model. Then, the crack resistance of a timber CTS (Compact Tension Specimen) is investigated to show the efficiency of the proposed approach in the case of orthotropic material

An indentification technique for mechanical characteristics of wood in room temperture

International audienc

Reliability-Based Design of Structures Under Seismic Loading: Application to Timber Structures

A reliability approach applied to wood structures under seismic excitation is proposed in this paper. This approach is based on First Order Reliability Method (FORM). The mechanical, model which represents a timber roof truss used in individual housing, is detailed and the mechanical nonlinear behavior of the timber joints is defined by hysteresis elements. The uncertainties are taken into account in the numerical model through random variables representing the stiffness parameters at timber joints. The reliability analysis allows us to compute the failure probability and their sensitivity to various random parameters. Numerical examples show the performance and the efficiency of the proposed method

Couplage numérique et expérimental pour l’évaluation probabiliste des structures bois sous chargement sismique

This paper presents a two-step probabilistic approach to deal with problems involving high-dimensional input parameter spaces. Firstly, the effective stochastic dimension is identified using a screening method. The most important parameters are then modelled as random variables and the others are represented by their mean values. Then, the variability of the model response is evaluated by the decomposition method. This approach is used to assess the integrity of timber roofs of residential houses under seismic event. The seismic loading is modelled by real earthquake ground motion records representing the seismic hazard of the city of Le Moule in Guadeloupe. The variability of the damage accumulated in the structure is properly assessed by computing the statistical moments and the construction of the probability density. The results have shown that the uncertain parameters have significant effect on the variability of the damage accumulated in timber joints located on the bracing members. In addition, the damage variability and the PGA near-collapse are closely correlated. Finally, the probabilistic computation results have been used to construct fragility curves, which are very useful for the design of timber roof