Effects of bond-slip and loading history of constituent materials for RC beams subjected to blast and impact loads

Abstract

In this paper, an improved numerical model for the nonlinear analysis of reinforced concrete (RC) beams subjected to blast and impact loadings is introduced on the basis of the layered section approach. The dynamic increase factor (DIF) is introduced to describe the dynamic material behaviors of concrete and steel. Unlike the classical layered section approach that usually gives conservative structural responses because of perfect bond assumption, the proposed numerical model considers bond-slip between reinforcing steel and surrounding concrete by changing the bending stiffness EI of elements placed within the plastic hinge length. Since the bond-slip developed after yielding of reinforcing steel is dominant and accompanies fixed-end rotation, the equivalent bending stiffness in the critical region can be evaluated on the basis of the compatibility condition. In addition, the consideration of the unloading and reloading histories of reinforcing steel and concrete makes it possible to exactly trace the structural behavior even after reaching the maximum structural response. Finally, correlation studies between analytical results and experimental data are conducted in terms of the mid-span deflection and time histories to establish the validity of the introduced numerical model, and the obtained results show the importance of considering the bond-slip effect and the loading history of constituent materials.