Falling mass bearing capacity of reinforced concrete beams

•Accidental impacts.•Accurate and easy-to-apply closed-form analytical formulation.•Existing RC beams are vulnerable to impacts.•Mass that hits a beam.•Prediction of tolerable mass and velocity of impacts. This paper is devoted to Reinforced Concrete (RC) beams that can be subjected to accidental falls of substantial masses (hard impacts at low velocities), such as the beams of bridges, industrial buildings, or factories. Here the reference is to existing RC beams, which have no purposely designed reinforcement to resist impacts. The paper focuses on a mass that falls around the midspan, where the capacity of a RC beam to resist an impact is minimum, due to a potential primarycracking pattern that consists of vertical cracks. The impact here is defined by the combination of the mass that falls down and its velocity at the impact. The paper provides an analytical formulation to predict the combinations that trigger the collapse of a RC beam (i.e., ultimate combinations). After having framed the research question, the paper presents the two possible failure modes, the derivation of the equations, the sensitivity of the bearing capacity to the main parameters, comparisons with existing results from literature, and two applications, whose results are discussed.