Impact behavior of shear-failure-type RC beams without shear rebar

In this study, to establish a rational impact-resistant design procedure of shear-failure-type reinforced concrete (RC) beams, falling-weight impact tests were conducted. Twenty-seven simply supported rectangular RC beams without shear rebar were used. All RC beams were of 150 mm width and 250 mm depth in cross section, with rebar and shear-span ratios taken as variables. An impact load was applied at the mid-span of the RC beam by dropping a free-falling 300 kg steel weight. In these experiments, the impact force excited in the steel weight, the reaction force, and the mid-span displacement were measured and recorded by wide-band analog data recorders. After testing, crack patterns developed on the side-surfaces of the RC beams were sketched. The results obtained are as follows: (1) the shape of the hysteretic loop between the reaction force and the mid-span displacement can be assumed to be triangular when the RC beam collapses due to severe diagonal cracks developed from the loading point to the support points; (2) shear-failure-type RC beams without shear rebar under impact load can be designed with a certain safety margin by assuming a dynamic response ratio of 1.5 and an absorbed input energy ratio of 0.6; (3) the required static shear capacity for RC beams against impact load can be evaluated by a proposed simple equation.