Modified Empirical Formula for Prediction of the Maximum Deflection of RC Beam Subjected to Low-Velocity Impact Loading

Recently, the interest in impact resistance design of structures is on the rise due to the increase in terror and collision accident, such as rock falling, collision of car, ship, and aircraft. Structural behavior under impact load conditions is very different from static load conditions. Consequently, the guidelines designed for static loads are not applicable to impact resistance design. There are UFC-3-340-02 and ACI 349-13 for impact resistance design, but these two are guidelines for high-velocity impact loads with special facilities such as military and nuclear power plants, respectively. Therefore, there are no guidelines for impact resistance design to infrastructure with a relatively high risk of low-velocity impact load. In order to propose guidelines for impact resistance design of infrastructure, performance-based design methods have been proposed through the maximum deflection of members under low-velocity impact loading. As a performance-based impact resistance approach, studies for the prediction of the maximum deflection of RC beam subjected to low-velocity impact loading by empirical formula have been conducted by many researchers. The simple equation to predict maximum deflection expressed as a ratio of impact energy and static flexural strength was proposed in many studies. To consider variables affecting the maximum deflection, the modified equation considering the additional variables, such as momentum of impact loading, cross-sectional size, concrete strength, was also suggested. However, these equations cannot reflect the effect of flexural stiffness affecting the member deflection. Therefore, in this study, the effect of flexural stiffness of RC beam on maximum deflection was experimentally investigated under different impact energy using drop weight impact tester. Finally, new empirical formula was proposed by modifying the previous empirical formulas based on the drop weight impact test. Previous and newly proposed empirical formulas were compared and analyzed through previous research data, confirming that the newly proposed empirical formula predicts well than other formulas. The empirical formula proposed in this work can be sufficiently utilized to predict maximum deflection over a wide range of variables.