地震动脉冲参数对近断层区深水桥墩动力响应的影响分析

Influence of Pulse Parameters on Dynamic Response of Bridge Pier in Deep Water Excited by Near-fault Earthquakes

本文采用基于流固耦合理论的势流体计算方法,以某典型铁路深水桥梁为研究对象建立墩-水作用模型,引入人工合成近断层等效速度脉冲方法,量化分析并提炼脉冲参数对深水桥墩动水压力及结构地震响应的影响规律。研究表明:脉冲效应有可能使结构动力响应成倍增大,脉冲峰值Vp、脉冲周期Tp和脉冲类型等3类脉冲参数对深水桥墩动力响应均存在明显影响。随着脉冲峰值Vp的增大,不同水深下桥墩结构的动力响应均增大;当脉冲周期Tp接近桥墩结构自振周期时,其动力响应被明显放大;对于本文算例,C类脉冲的影响最明显,B类次之,A类最小。结合反应谱分析可知,不同脉冲参数的影响方式和幅度有所差别,一定程度上可以根据脉冲波反应谱的频谱强度及周期分布特征解释。进行近断层区深水桥梁抗震设计时,应对比检验不同类型脉冲参数的潜在影响,确保桥梁地震安全。

With a typical railway bridge in deep water as an example, a pier-water interaction model was estab- lished using potential-based fluid method based on fluid-structure interaction theory. The influence of pulse parameters of near-fault ground motions on hydrodynamic pressure and earthquake response on the equivalent pier was quantitatively analyzed, using artificially synthesized near-fault equivalent velocity pulse method. The results showed that the dynamic response of structure may be multiplied under pulse effect. Three kinds of pulse parameters, such as pulse peak Vp, pulse period Tp and pulse type, had great influence on the seismic behavior of pier. With the augmentation of Vp, the dynamic response of piers increased under different water depths. When Tp was close to the natural vibration period of pier, the dynamic response amplified significantly. For this pier example, C-type pulse had the greatest effect, with the B-type pulse showing the second greatest effect, and A-type pulse showing the minimal effect. Combined with response spectrum analysis, the ways and magnitude of influence for each pulse parameter were different, and these could be explained from the distribution characteristics of intensity and spectrum period of impulsive ground motion. Therefore, for the seismic design of deep-water bridges in near-fault zone, potential influence of different pulse parameters should be contrastively discussed to ensure the safety of bridge structures.