高桩承台桥梁船撞动力需求的时程分析法

Development of Time History Analysis for Dynamic Demand of Elevated Pilecap Bridge Subjected to Vessel Collision

摘要:

船撞桥问题涉及到材料、几何和边界条件的非线性,造成了整船碰撞有限元模型不但计算效率低下,而且较难为工程师所接受.鉴于此,提出采用简化的时程分析法来帮助设计者快速准确地掌握桥梁结构在船撞作用下的动力需求.在构建时程分析法过程中,首先基于两自由度碰撞分析模型,建立了基本的能量守恒方程和动量守恒方程.以能量守恒方程和构建的动力撞击力和撞深曲线(Pda曲线)为依据,确定了船艏的最大撞深,并对结构弹性变形能的考虑进行了讨论.根据假定的加载时撞深与时间的关系和卸载时撞击力与时间的关系,推导了船撞作用加载和卸载的持时计算公式.总结形成了基于时程分析法计算高桩承台桥梁船撞动力需求的一般性程序,并将其运用工程实例中.工程实例计算结果表明：时程分析法计算所得的结构动力响应与整船碰撞模型结果基本一致,且计算效率较高.

Abstract:

Generalpurpose nonlinear finiteelement model is characterized by its low efficiency and material,geometric and boundary nonlinear behaviors in shipbridge collision,which is unacceptable to engineers.An alternative timehistory approach is presented to rapidly and reliably evaluate the dynamic demand of bridge structure under ship impact.Energy conservation and momentum conservation equations are established based on the model of two degrees of freedom(DOFs).Then,based on energy conservation equation and the relationship between dynamic impact force to crush depth(namely,curve),the maximum crush depth is determined and the structural elastic potential energy is also discussed.According to the assumed timecrush depth relationship during loading and timeimpact force relationship during unloading,formulae of the time duration of loading and unloading under ship collision are obtained.A procedure of calculating the dynamic demand of bridges is proposed for practical project.Results show the dynamic responses of structure by the proposed method are in agreement with the shipbridge collision model,but the computation efficiency is improved obviously.