Contrast of concrete dynamic constitutive models and simulation of vessel-bridge collision

Long-span bridges are constructed to cross oceans or rivers. With the rapid growth of waterway transportation, vessel-bridge collision incidents now occur in large numbers. In order to provide better understanding of the actual responses of bridge structures under impact load, vessel-bridge collisions were simulated using the non-linear finite-element method. Four commonly used dynamic constitutive models of concrete are described in this paper. Two impact tests (a rigid ball striking a target concrete wall and a hammer striking a reinforced concrete (RC) beam) were simulated using LS-Dyna. It was found that the RC damage model was more suitable for simulating the inelastic responses of cracks than the other three models. Based on the RC damage model, a typical bridge substructure subjected to a 1000 dead-weight-tonnage vessel collision was numerically simulated. An empirical formula for estimating the maximum impact force was then developed. This formula, which considers the reinforcement ratio and the vessel collision velocity, is suggested for practical vessel-bridge design. The proposed empirical formula and the equations recommended in codes from different countries were compared and it was found that the assessment of vessel collision force using the new formula is significantly improved.