PhD defense : Modelling of nominal strength prediction for quasi-brittle materials. Application to discrete element modelling of damage and fracture of asphalt concrete under fatigue loading

PhD defense : Xiaofeng GAO

Team : GCE

Title : Modelling of nominal strength prediction for quasi-brittle materials. Application to discrete element modelling of damage and fracture of asphalt concrete under fatigue loading

Abstract : The prediction of the fatigue life and the rupture of structures made of quasi-brittle materials (hydraulic or bituminous concretes, rocks, certain types of ceramics, etc.) are subjects that are continuously evolving and hence, require the development of new theoretical and numerical models. In this work, the modeling of the crack initiation and propagation under monotonic loading is firstly investigated. An expression for geometrically similar specimens is directly established, which allows the comparison of the proposed model with experimental results from the literature (three-point bending of cracked beams) and other models that characterize the size effect. The use of an additional parameter in the model allows the analysis of the rupture mechanism for structures with defects more complex than a crack. The predictions of the proposed model are compared with experimental results from the literature for various specimens (intact or pre-cracked) of different materials and sizes. Samples with initial V-shaped and hole-shaped defects exemplify the formulation's capabilities. Then, the damage and cracking induced by cyclic fatigue loads is discussed. A local model using discrete elements is developed, that allows the coupling of two mechanisms (damage and fatigue cracking). The numerical results are compared to those of experimental bending fatigue tests. Finally, applications associated with the behavior of fiber glass reinforced asphalt concrete are analyzed in detail.

This thesis was supervised by Cyrille Chazallon (INSA of Strasbourg) and co-diriged by Yannick Descantes (IFSTTAR).

The presentation will be held in English on Monday, March 6th, at 1:30 p.m. in the Amphitheater De Dietrich at INSA Strasbourg.