Plastic hinges and inertia forces in RC beams under impact loads

This study investigates the impact behavior of reinforced concrete beams and proposes a procedure to derive the shear force and bending moment diagrams. The assumption of linear distribution of the inertia force under impact load is examined against experimental and numerical results. The finding in this study has confirmed the linear inertia force distribution assumption along the beam up to the instant the impact force reaches its peak value. The position of plastic hinges is observed to have significant effects on the impact behavior of the beam. Under impact the plastic hinge does not necessarily reach the supports, and then only part of the beam within the stationary points is accelerated while the rest of the beam remains stationary. A procedure is proposed to predict the position of the stationary points, which is proven yielding reasonable results in comparison with experimental and numerical results. A flow chart is also provided to generate the shear force and bending moment diagrams for reinforced concrete beams under impact loads, which can be used in the design of concrete beams subjected to impact loads.