深水桥梁空心高墩流固耦合振动特性与地震响应分析

Study on Vibration Characteristics and Seismic Response of Deep-water Hollow High Bridge Pier Considering Fluid-structure Interaction

为研究动水压力对深水高墩结构振动特性与地震响应的影响规律,以一典型深水圆形空心高墩为例,采用基于势流理论的完全数值法,建立了深水圆形空心高墩-水流固耦合数值分析模型,探讨了在墩身仅外有水、仅内有水以及内、外均有水3种情况下,桥墩结构的振动特性与地震响应的变化规律。研究结果表明:墩-水耦合作用使得桥墩结构各阶振型周期有所增大,墩身内、外均有水时增幅最大;随着水深的增大,桥墩结构的地震响应总体上是增大的,且内、外均有水时增幅最大;上部结构质量总体上降低了动水压力对结构地震响应的影响;当水深小于墩高一半时,桥墩低阶振型周期变化很小,但其高阶振型周期变化较大;高阶振型对高墩底部地震剪力贡献较大,因此,当水深不大时应当重视动水压力对高墩底部地震剪力的影响。

In order to investigate the influence rules of hydrodynamic pressure on vibration characteristics and seismic responses of deep-water hollow high pier, in this paper a typical deep-water circular hollow high pier was taken as an example and the numerical models considering pier-water interaction were built based on potential flow theory. The vibration characteristics and seismic responses of deep-water hollow high pier were investigated respectively considering three cases such as only with water outside the hollow pier, only with water inside the hollow pier, with water both inside and outside the hollow pier. The research results indicate that the hydrodynamic pressure increases the modes vibration peri- ods of the pier and the maximum increase rate is the case considering both out-water and in-water. Superstructure mass diminishes the effect of hydrodynamic pressure on structure seismic response. The low-order-mode periods of pier change slightly when water lever is under half of the pier height. However, the high-order-mode periods cannot be neglected for the high-order modes, which contributes a lot to the shear on the bottom of the pier. Therefore, great importance should be attached to the effect of hydrodynamic pressure on the bottom shear of high pier when water depth is not big enough.