A new computational approach towards the simulation of concrete structures under impulsive loading

Extraordinary actions such as blast loadings and high velocity impact are rare, but usually have devastating effects. Thus, making critical infrastructures, such as military and governmental facilities, power-plants, dams, bridges, hospitals, etc., more resilient against these hazards is one of the best ways to protect ourselves and our societies. Since concrete is a very common construction material, the development of realistic numerical tools to efficiently simulate its failure behavior under extreme dynamic loading conditions is of paramount importance, but still a major challenge.
This thesis presents a new stress-based nonlocal effective rate-dependent damage model, developed to simulate the dynamic response and failure of concrete during ballistic impact. The proposed isotropic damage formulation combines the effect of three damage modes: (i ) tension (mode I), (i i ) compressive-shear (mode II and mixed-mode) and (i i i ) hydrostatic damage to describe crushing of the cement matrix under pressure. The strain-rate dependent update of the constitutive relations to express the dynamic increase of strength and fracture energy in tension and compression is made a function of an effective rate, instead of the commonly used instantaneous strain rate. An enhanced version of the stress-based nonlocal regularization scheme is used to correct spurious mesh sensitivity. The proposedmodel was developed solely in the effective strain-space, following an entirely explicit computation scheme.