跨海特大型桥梁风-浪耦合作用的随机振动分析

考虑风-浪耦合场中风和波浪特征参数的相关性，建立了基于有限元法与边界元法联合分析的特大型桥梁风-浪耦合作用运动方程.其中，作用在大型深水基础上的波浪力采用势流理论和边界元法进行计算，并建立有限单元与边界元单元组的映射关系，将边界单元组上的波浪力映射到结构有限单元上；作用在桥梁上的气动力通过有限元法进行计算，包括由脉动风激发的非定常抖振力和由气弹相互作用产生的自激力.在此基础上，基于随机振动分析的高效算法——虚拟激励法，建立了计算桥梁风-浪耦合作用响应的分析方法.最后，针对某跨海超大跨桥梁方案进行研究，结果表明:与风致响应相比，风-浪耦合作用下桥梁深水基础内力显著增大，其中波浪激发的侧向剪力占主导地位，波浪激发的侧向弯矩在海床附近与风致响应基本相当，但在海床以下更大；斜风-波浪耦合作用下的主梁内力响应和深水基础内力响应比正交风-波浪耦合作用下的结果更大.因此，在跨海桥梁设计中，必须考虑风-浪耦合作用效应.

An Analysis Method for Wind-Wave Coupling Induced Random Vibration of Sea-Crossing Super-Large Bridges

The motion equation for wind-wave-bridge coupling systems was established, based on the combination of the finite element method and the boundary element method, to consider the characteristic parameters’ correlation of the wind-wave coupling fields. In turn, the wave induced force acting on the large-scale deepwater foundation was calculated according to the potential flow theory and the boundary element method firstly, then transferred to the finite element model of the foundation based on the finite/boundary element mapping relation; the aerodynamic forces acting on the bridge were calculated with the finite element method, including the fluctuating wind induced unsteady buffeting force and the aeroelasticity interaction induced self-excited force. By means of the pseudo-excitation method, the random vibration analysis framework for the wind-wave-bridge coupling system was developed. A sea-crossing super-large bridge scheme was taken for example. The research shows, the wind-wave coupling induced bridge foundation internal forces are significantly larger than those induced by wind alone, of which the shear forces are mainly caused by wave, and the lateral moments caused by wave are equal to those caused by wind near the seabed but are larger below. So, the wind-wave coupling effects should be considered in the design of sea-crossing bridges.