Yann Malécot

Strength and damage of concrete under high triaxial loading

ABSTRACT This study focuses on identifying concrete behavior under severe loading (near field detonation or ballistic impacts). In order to reproduce high stress levels with well-controlled loading paths, static tests are carried out on concrete samples by mean of a very high-capacity triaxial press. Experimental results indicate a sizeable change in concrete behavior with confining pressure. At low pressure values, the concrete exhibits brittle behavior with failure caused by a localized damage mechanism. In contrast, at high confining pressures, the concrete becomes a ductile material, and failure is associated with diffuse material damage. These tests also show an evolution of the elastic characteristics of concrete. A numerical modeling of these previous experiments is performed at a mesoscopic scale. It provides a reproduction of the main characteristics of concrete behavior under high confinement, both qualitatively and quantitatively.

Concrete structures under impact

ABSTRACT The upcoming need of concrete structures designed against impulsive loading such impact requires analytical treatments comparable to those existing for structures under static loading in spite of a poor state of knowledge of material behaviour in this range of loading. This paper first presents basic relations and empirical formulae used by civil engineers for the design of concrete structures under impacts. Experimental analyses of concrete behaviour under high triaxial stress and high strain rates show that empirical formulae have to be used with care. Some recent numerical developments are also shown.