动水力简化计算方法对圆形桥墩地震反应的影响

Effects of Simplified Methods for Hydrodynamic Force on Seismic Responses of Circular Piers

基于不可压缩水体的假定条件,国内外研究者提出多种可供工程实用的动水力简化分析模型和计算方法,如刚性柱法、莫里森法和基频近似法等.为研究上述简化方法所得桥墩动力响应的差异,将基于不可压缩水体辐射理论得到的精确解作为标准,针对受水平地震动激励的水中弹性悬臂圆形桥墩进行地震响应的对比分析.选取对动水力有影响的水深和宽深比,通过输入3条中软土场地的地震动记录,总共设计144种不同尺寸的桥墩、水深以及地震作用工况,得到各工况下桥墩的顶部位移、底部剪力和弯矩响应.通过对顶部位移、底部剪力和弯矩响应峰值相对误差的范围、均值和变异系数的分析讨论,得到3种简化方法的计算精度,初步给出各方法的适用范围.

For engineering applications, a variety of simplified analysis models and calculation methods considering the hydrodynamic force have been proposed based on the assumption of incompressible water. Some typical methods include the rigid-structure method, Morison method and a method based on approximation of fundamental-frequency. The seismic responses of elastic cantilever circular piers excited by horizontal earthquake were analyzed to study the difference caused by the above methods. By using 3 ground motion records on soft soil site and selecting a series of depth and wide-depth ratio as parameters, 144 cases of bridge piers were considered. The horizontal displacement at the top of the piers, shearing force and bending moment at the bottom were compared with the exact solutions based on the radiation theory of incompressible water. Then, the range, mean values and coefficient of variation of the relative errors of the peak values of responses were presented. Based on the analysis of errors, calculation accuracy of the simplified methods was investigated and the applicable scope was given preliminarily.