桥梁抗震分析中动水压力的计算

Calculation of Hydrodynamic Pressure in the Seismic Design of Bridge

用势流体单元模拟水体,采用数值分析方法计算分析地震动水压力。采用Morison方程法,以附加质量的形式考虑动水压力。运用两频段选波方法,选取美国Spitak(1988)和Imperial Valley(1979)2条地震波,进行深水桥墩地震响应分析,研究动水压力对深水桥墩地震响应的影响。结果表明:在地震作用下,动水压力显著增大桥墩的墩顶位移和墩底内力响应,且使地震响应峰值出现的时刻有所改变。在进行抗震设计时考虑动水压力的作用是非常必要的。通过对实际桥墩的分析,验证Morison方程法在深水桥墩地震响应分析中的有效性,说明按照我国现行铁路工程抗震设计规范中的计算方法得出的深水桥墩地震响应结果偏低。

The potential flow element is used in the finite element method to imitate water so as to study the hydrodynamic pressure excited by earthquake, and the famous Morison Equation is also used to analyze hydrodynamic pressure where as a simplified method the water is considered as the added pseudo mass. The seismic response of an actual bridge pier is analyzed to study the impact of hydrodynamic pressure on the earthquake response of bridge piers in deep water by two-frequency range wave selection method, choosing the earthquake waves of Spitak （1988） and Imperial Valley （1979） of USA. Results show that under earthquake, the hydrodynamic pressure can remarkably increase the displacement of pier top and the internal force response of pier bottom, and change the occurrence time of earthquake response peak value. The effect of hydrodynamic pressure of bridge piers is of vital importance in seismic design. Through actual analysis of certain bridge pier, Morison Equation method has been to be effective in analyzing the earthquake response of bridge piers in deep water. However, the responses results estimated according to current Chinese seismic design code tend to underestimate the hydrodynamic pressure on bridge pier in deep water.