Experimental study on the behavior of high strength reinforced concrete beams under impact load

To explore the shear-resistant behavior of RC beams under impact load, six simply-supported high strength RC beam with various shear reinforcement ratios, were tested under free-falling drop-weights, impacting the specimens at mid-span, and the effects of impact mass and impact energy on the shear resistant behavior of RC beams were investigated. The crack initiation, propagation and the failure patterns of the specimens were recorded using a high-speed video camera. The characteristics of time history of impact force, support pressure and mid-span displacement were described in details. The results obtained are as follows: Experimental studies reveal that shear mechanisms play an important role in the overall impact behavior of RC structures. Severe diagonal shear cracks occur even with statically flexural-critical RC beams tested under impact loads applied at the mid-span. Increase of concrete strength has less effect on the degree of overall failure, but it can reduce the specimen local failure near the impact loading point; This article summarizes the result of independent impact load experiment on the RC beam. It draws out the index that significantly influences between the maximum mid-span displacement and the static ultimate bending strength. It contributes to the impact resistance design method for simply-supported RC beam performance verification; During the initial stage before the external force reached the supports, the impact forces acting on the RC beam were mainly resisted by the inertia force of the specimens. The stiffness of a structure and the span length of a beam are important factors in resisting impact forces. ©, 2014, Tianjin University. All right reserved.