极端波浪作用下海上施工栈桥承载性能评估

海上施工栈桥作为一种可以快速装配的施工辅助设施,在跨海大桥建设中得到广泛应用。为研究海上施工栈桥在极端波浪作用下的结构性能,基于波浪增量分析(IWA)理论,提出海上施工栈桥承载性能评估方法。以某在役海上施工栈桥为例,考虑杆件弹塑性和节点局部柔性建立结构非线性分析模型,评估了海上施工栈桥在不同方向极端波浪荷载作用下的结构承载性能及倒塌失效模式。研究表明,随着极端波高逐渐增大,栈桥依次出现首次屈服、塑性铰和倒塌起始三种非线性行为点,结构将依次经历正常使用、可以使用、临近倒塌和倒塌破坏四个承载性能状态;波浪入射方向对于海上施工栈桥的承载性能和倒塌失效模式影响较大;海上施工栈桥的主要薄弱部位位于钢管桩桩底及其与支撑框架下横撑相交的节点处,应在设计中重点关注。

Performance assessment of bearing capacity of offshore construction trestle under extreme waves

As a constructional auxiliary facility which can be quickly assembled, the offshore construction trestles have been widely used in the construction of sea-crossing bridges. In order to study the structural performance of offshore construction trestles under extreme waves, a method for assessing the performance of bearing capacity of offshore construction trestles was proposed based on IWA theory. Taking an in-service offshore construction trestle as the example, considering the elastic-plastic behavior of members and local flexibility of joints, a structural nonlinear analysis model was established to assess the performance of bearing capacity and collapse failure modes of the trestle under extreme wave loads propagating from different directions. The results show that with the increase of extreme wave height, three nonlinear behavior points, i.e. first yield, plastic hinge and collapse initiation, appear successively, and the structure would undergo four performance states of bearing capacity, i.e., normal use, immediate operation, near collapse and collapse failure; the direction of wave has a great influence on the performance of bearing capacity and collapse failure modes of the offshore construction trestle; and the main weak parts of the offshore construction trestle are located at the bottom of steel pipe piles and the joints between the bottom crossing braces and piles, which should be paid attention to in the design.