SMEARED CRACK ANALYSIS FOR REINFORCED-CONCRETE STRUCTURES UNDER BLAST-TYPE LOADING

A smeared crack analysis is presented for the nonlinear finite element analysis of plane and axisymmetric reinforced concrete structures under blast and impulsive loading conditions. Based on the fixed crack approach, a rate dependent strain criterion is proposed to serve as a crack initiation condition. The crack propagation is governed by nonlinear reversible formulations to model concrete tension softening as a function of concrete fracture energy, tensile strength, cracking strain and crack characteristic length. Shear transfer due to aggregate interlock and dowel bars is simulated by a nonlinear model dependent on the strain across the crack. Other computational features are considered, such as closing and opening of existing cracks, compressive behaviour of cracked concrete, control of a stress locking phenomenon, and detection of active and arrested cracks to reveal a fracture localisation mechanism associated with shear-type cracks. The constitutive relationships for cracked concrete are derived for the possible different crack configurations. A new crack monitoring algorithm, as part of a comprehensive computer program FEABRS, is developed which follows the cracking behaviour with the time stepping scheme. The results of some dynamic applications are presented and compared with those from other numerical and experimental sources.