Dynamic Demand of Bridge Structure Subjected to Vessel Impact Using Simplified Interaction Model

Assessing the dynamic demand using general-purpose finite-element codes is not only low in efficiency, but also unaccepted in practical application due to the complicated nonlinear dynamical behaviors of vessel-bridge collision. In this paper, an alternative simplified interaction model is presented to evaluate the dynamic demand of bridge structure under vessel impact efficiently. In this method, ship motion is regarded as the motion of single degree of freedom, and ship-bow is modeled by a nonlinear spring element (only compression) connected to bridge structure. A quasi-static method is employed to obtain the nonlinear static relationships between impact forces and crush depths of ship-bow, and the effect of the height of pile cap is discussed. Based on two different approaches, the influence of strain-rate effect on impact force is taken into account to obtain the corresponding dynamic crush curves, which are developed for the proposed interaction model. Results show that the dynamic responses of bridge structures using the simplified interaction models are in good agreement with the general-purpose collision analyses, while the former computation efficiency is improved obviously.