Mechanical model for predicting wave loads on complex pile group foundations under linear wave action

Abstract

Pile group foundations of offshore bridges have complex geometries and are subjected to enormous wave loads for a long time. Therefore, the accurate and efficient prediction of wave forces on pile group foundations is related to the economic design and safe operation of sea-crossing bridges. In this study, a mechanical model for predicting wave loads on complex pile group foundations under linear wave action is developed. At first, a three-dimensional hybrid technique combining the eigenfunction expansion method and the boundary element method is proposed for analyzing the wave diffraction problem from the large-scale pile cap. Based on this, the modified Morrison equation is utilized to solve the wave forces on piles. Meanwhile, the wave loads on the pile group are obtained by considering the pile group effect. The presented model is then employed to calculate the wave forces on cylindrical caps and piles below a square cap, and the calculation results match well with the published results, which illustrates the validity of the presented model. Finally, this model is extended to practical engineering applications. That is, the wave load characteristics on a pile group foundation with a quasi-elliptic cap and 13 tilted piles are systematically analyzed under different wave conditions. This study exhibits that the presented mechanical model can effectively calculate and output the wave loads on each component of the pile group foundation, and the calculation results can provide the data support for the design and optimization of complex pile group foundations.