Author(s)

W. Fan & W. C. Yuan

Abstract

An equivalent static force is usually used to represent vessel-impact load exerted on bridge structures in current bridge design codes. However, this static procedure using the code-prescribed loads cannot consider dynamic effects (e.g. inertial force related to superstructure mass). Hence, the vessel-impact responses of bridges may be significantly underestimated and the structural safety cannot be warranted in practice. In this paper, a simple procedure is proposed to define the dynamic ship-impact loads on bridge structures. Firstly, the equations to determine the duration of loading and the maximum ship-bow crush depth are developed based upon principles of conservation of energy and linear momentum during a collision event. Using the above equations and the relationships between crush depth and time, the dynamic ship-impact loads are determined based on ship bow force-deformation curves (P-a curves). For the generated ship-impact load histories, the amplitude, duration and frequency spectra are compared with the results from the high-resolution finite element analyses of ship-bridge collisions. It is found that these parameters are in good agreement with the high-resolution analysis results and the developed procedure can be readily employed to determine the vessel-impact responses of bridge structures like the time history analysis in seismic design. Keywords: impact load, ship collision, bridge structure, P-a curve.

Keywords

impact load, ship collision, bridge structure, P-a curve.