Performance of reinforced concrete beam with cushion subjected to impact loading

Many countries are developing new ways to protect Reinforced Concrete (RC) structures under specific risks such as rockfall hazards. Cushioning materials, for example, are using to improve the impact resistance of the RC structures. Applying cushions improves the strength of RC structures under aging of materials and deteriorations, therefore, it improves the safety of people, buildings, and infrastructure systems. However, the impact resistance of RC structures with cushions have not yet been clarified. This study aims to clarify the effect of four types of high strength expanded materials, three are Polystyrene and one is Polycarbonate, which were set on RC beams to enhance impact resistance of the beams. Drop weight tests were employed to investigate the mechanical behavior of RC beams with cushions. The following conclusions were found based on the results of this study: 1) High energy absorbing cushions should be used to protect RC beams subjected to impact loadings as it significantly reduced the maximum deflection and crack opening process of the beams. 2) The hardening effect of concrete at upper cover surface of RC beam during collision were confirmed by using yielding static test. It is used to calibrate static fiber model of normal RC beam to obtain the maximum deflection due to impact loadings. 3) The impact absorbing energy of the cushions were verified to establish simplified equation of maximum deflections of the beam with cushions. 4) The estimated maximum deflections of RC beams with and without cushions are in agreement with the measured values.