Impact behavior of no-stirrup Reinforced Concrete Beam with Cushion

The purpose of this study is to clarify impact response of no-shear-reinforcement reinforced concrete (RC) beams having cushion layers subjected to impact loading. The beams, which are designed with Polystyrene (Beam S type) and Polycarbonate (Beam P type), were tested by drop-weight experiment with various height of impact at 4.0, 4.5 and 5 m compared to no-cushion-designed beam (Beam N) at accordingly impact velocities. The weight of 169 kg was free falling to mid-span of the beams which have dimension of width, depth and clear span length are 150, 250 and 2000 mm. After testing, crack patterns propagated from the side surfaces of the RC beams was sketched, and impact forces, reaction forces and mid-span deflection was measured and recorded by wide-band analog data recorders. In addition, a comparative static loading test of no-stirrup beam (Beam NS) was used to establish an analytical fiber model of the beam under impact loading. The results obtained are as follows: 1) No-stirrup RC beams governed by shear-failure-mode or combined shear- and flexural- failure mode with diagonal cracks, while those with cushion almost exhibited flexural-failure-mode with significant fewer cracks; 2) At velocity of 4 m/s, no-cushion-designed beam’s performance indicate the yielding stage in brittle failure mode of no-stirrup RC beam; 3) To quantitively estimate the contribution of the cushion on the beam have and have-not cushion, a proposed simplified fiber model was used with comparison to its static performance in order to determined maximum deflection of the beams; 4) It is assumed that initial dissipated energy does not occurred in beams have cushion, while beams have-not cushion own this due to its brittle failure mode; 5) It is found that estimated maximum deflections of the beam are in line with the measured values; 6) Dynamic absorbed energy of the cushion are higher than static absorbed energy of the cushions, which lead to higher contribution of the cushion in impact event.