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动水效应是深水桥梁抗震设计中需要考虑的重要问题,而近场地震下深水桥墩的响应特性及合理计算方法亟待研究。以某典型深水桥梁为对象,基于可有效考虑墩-水流固耦合效应的完全数值计算方法,建立其等效单墩模型。首先讨论了水域范围对结构自振频率计算结果的影响,然后分析了不同水深下桥墩自振特性及脉冲型近场地震下的响应特征,并检验了几种代表性的解析-数值方法的准确性。研究结果表明:当水域宽度达到桥墩直径的10倍时,自振频率计算结果保持稳定;桥墩自振频率随水深增大而减小,桥墩完全被水淹没时前3阶自振频率分别比无水时减小了5.3%、12.2%和17.9%;不同方法下各阶频率的误差率随水深增大总体呈增大趋势,日本规范所得频率偏大,最大误差率超过20%,Morison方程法所得频率偏小,辐射波浪理论、中国铁路规范所得频率值与流固耦合数值法接近;近场地震下,桥墩弯矩、剪力和位移响应比无水时分别增大了22%、23%和20%,Morison方程法计算结果偏大,其最大误差率超过6%,日本规范计算结果偏小,最大误差率接近-5%,辐射波浪理论、中国铁路规范及李乔-杨万理简化公式所得结果与流固耦合完全数值法相吻合,5种方法均可适用于一般尺度深水桥梁的抗震设计。研究成果对于近断层区深水桥梁的抗震设计具有借鉴意义。
The hydrodynamic effect is an important issue to be considered in the seismic design of deepwater bridges. However, the response characteristics and reasonable calculation methods of deepwater piers under near-field earthquake need to be studied urgently. Taking a typical deepwater bridge as an example, an equivalent single pier model is established based on a complete numerical method that can effectively consider the coupling effect between pier and water. Firstly, the influence of water area on the natural frequency of structures is discussed. Then the self-vibration characteristics of bridge pier under different water depths and the response characteristics under impulsive near-field earthquakes are analyzed. Several representative analytical-numerical methods are also tested Sex. The results show that when the water width reaches 10 times the diameter of bridge piers, the results of natural frequencies remain stable. The natural frequency of bridge piers decreases with the increase of water depth. When the piers are completely submerged, 5.3%, 12.2% and 17.9% in water, respectively. The error rate of each order under different methods tends to increase with the increase of water depth. The frequency of the Japanese code is larger and the maximum error rate exceeds 20%. The Morison equation The obtained frequency is small, the theory of radiation wave and the frequency value of China Railway Code are close to that of fluid-solid coupling numerical method. Under near-field earthquakes, the moment, shear force and displacement response of bridge piers increase by 22% and 23% And 20%, Morison’s equation is too large, the maximum error rate of more than 6%, the Japanese standard calculation results are small, the maximum error rate is close to -5%, radiation wave theory, China Railway Code and Li Qiao - Yang Wanli simplified formula derived The results are in good agreement with the complete numerical method of fluid-structure interaction. All five methods are applicable to the seismic design of deep-water bridges with normal scale. The research results have reference significance for the seismic design of deepwater bridges near the fault zone.