开孔圆形截面空心桥墩水动力研究*

针对圆形截面空心桥墩壁上开孔后内部充水是否带来水动力的问题,采用ANSYS-CFX构建了墩-水耦合数值分析模型,并研究了内部水对空心墩的动力特性、地震动水力及响应的影响。结果表明:当水深一半时,空心墩自振频率相比仅有外部水时降低了25.08%,当满水时,空心墩自振频率降低可达39.32%。地震时,空心墩发生剧烈振动,内部水的晃动会增加结构的附加动水力,从而加大结构的动力响应(主应力增大率为30.84%);同时存在内外域动水的交换作用,使得通水孔附近局部应力较大(等效应力增加率为9%),内部水的影响已经掩盖过内部水平衡外部静压取得的应力改善效益,从地震作用效应的角度看,深水空心桥墩设计中不宜开孔。

Study on Hydrodynamic Characteristics of Circular Hollow Pier with Holes

For the problem whether inner water has an impact on the hydrodynamic characteristics of circular hollow pier with holes, a numerical analysis model for pier-water coupling by ANSYS-CFX wasestablished. The dynamic characteristics and the dynamic response of the hollowpier with inner water under earthquake loading were studied. The results show that the inner water has great influence on dynamic characteristics. When the inner water depth is half the height of the hollow pier, the natural frequency ofhollow pier is 25.08% lower than that of the only outer water, and the natural frequency is reduced by 39.32% with full water. As a result of pier vibration induced by earthquake, the inner water sloshing will increase the additional hydrodynamic force of the hollow pier, thus increasing the dynamic response of the structure (the increase rate of principal stress is 30.84%). The interaction between inner and outer water causes the local stress near the holes to increase by 9%.The benefit of inner water resistance to outer water pressure of the hollow pier is etched away. In terms of the seismic action effect, it is not suitable foropening holes on the wall of hollow piers in deep water.