深水悬臂桥墩动力特性及地震响应分析

利用ADINA中的势流体单元对一已建成的深水高墩建模,桥梁上部结构对桥墩的影响以墩顶集中质量的形式体现,分别对不同水深条件下桥墩-水体系的动力特性和地震动响应进行了系统的求解;为了检验Morison方程在深水桥墩动力分析中的有效性,将基于忽略速度力项的Morison方程的计算结果与基于势流体的结果进行了比较。研究结果表明：①水体对结构的自振频率折减影响随着水深的增大而增大,基于Morison方程得到的结构频率的影响大于势流体模型;②水深对墩顶位移的影响比加速度明显,墩底剪力受水深的影响大于其对墩底弯矩的影响;③考虑上部集中质量的影响,结构的响应会不同程度地减小;④相对于势流模型,忽略速度项的Morison方程所得到的结构动力反应略显保守。

Dynamic Characteristics and Seismic Responses of Cantilever Pier Immersed in Water

Based on ADINA,a finite element model for an existing high bridge pier immersed in water is made with potential fluid based element.A concentrated mass is attached to the top of the structure to simply simulate the bridge deck.A systematic study is carried out on the dynamic characteristics and seismic responses for various water depths.A simultaneous work is also done for the model on the basis of the Morison equation neglecting the velocity part and the result is compared with the PB model.Some conclusions are drawn：（1） The structural frequency is smaller in the presence of surrounding water,and this trend grows as water depth increases,meanwhile the corresponding result from the Morison model is more obvious than the PB model.（2） The top acceleration of the pier is more sensitive to water depth than the top displacement,and that also happens to base shear force compared with base moment.（3） Seismic response will reduce when including the effect of concentrated mass attached to the top of the pier.（4） Result of seismic responses for the Morison model is more conservative in contrast with the PB model.