动水对深水大跨刚构桥地震响应影响

Effect of Hydrodynamic Force on Long-span Deep-water Rigid Frame Bridge in Earthquake

深水大跨刚构桥在地震荷载作用下,水下结构部分与周围水体之间相互作用必然导致结构受到水体运动产生的动水力的作用。在已有Morison动水理论的基础上,利用深水大跨桥梁在动力荷载作用下的动水力简便计算方法,以某一大跨深水刚构桥为对象,分析了动水对刚构桥结构动力特性和地震反应的影响。主要结论有:水与刚构桥下部结构相互作用将使刚构桥自振周期有所增大,其中有水状态下桥梁第1阶自振周期相对无水时增大了4.72%;地震作用下动水对刚构桥结构内力有显著的影响,使桥墩底部弯矩最多增大了76.57%,平均增大了28.72%。并且动水使桥墩顶部位移平均增大了18.41%。且不同类型地震作用时,动水对桥梁动力响应的影响不尽相同。在深水大跨刚构桥进行抗震设计中,动水对桥梁动力响应的影响不容忽略。

When deep-water long-span rigid frame bridge suffers from seismic load, the interaction between underwater structure and surrounding water will inevitably lead to the hydrodynamic force applied to the structure. Based on the Morison hydrodynamic theory, taken a long-span deep-water rigid frame bridge as research object, the hydrodynamic effect on the dynamic characteristic and seismic response of the rigid frame bridge was analyzed using the simplified calculation method of hydrodynamic force. The main results show that （ 1 ） the natural vibration period of the rigid frame bridge was increased in the effect of the interaction of water and substructure in deep-water, the predominant period was enlarged by 4.72% relative to no water; （2） in the earthquake, the hydrodynamic effect on the internal force of the rigid frame bridge structure was significant in which the bending moment at the bottom of the pier was increased by 76.57% at maximum and the average bending moment was increased by 28.72%, and the displacement of the pier top was increased by 18.41% in average; （3） in different types of earthquake, the influence of hydrodynamic force on the dynamic response of the bridge was not identical. In the seismic design of long-span deep-water rigid frame bridges, the hydrodynamic effect on the dynamic response of bridges should not be ignored.