EXPERIMENTAL STUDY ON THE HYDRODYNAMIC PRESSURE OF BRIDGE PIERS UNDER EARTHQUAKES AND THE APPLICABILITY OF THE MORISON EQUATION
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摘要: 深水桥梁的抗震分析需要考虑地震作用下动水压力的影响。目前，广泛采用的Morison方程由波浪力的计算公式演化而来，用于计算地震动水压力尚缺乏验证；同时，对于地震作用下桥墩动水压力的变化规律缺乏试验研究。该文设计一套水下振动台试验系统，以不同尺寸的桥墩试件为研究对象，采用正弦波为输入激励，通过不同工况的振动台试验，研究桥墩加速度和地震动水压力的分布规律及其随激励幅值、激励频率、截面直径和水深的变化规律；将动水压力的试验结果与Morison方程的计算结果进行对比，以验证地震作用下Morison方程的适用性。结果表明：地震作用下桥墩加速度和动水压力应考虑激励幅值、激励频率、截面直径和水深的影响，Morison方程不适用于计算地震作用下桥墩动水压力，应通过大量的水下振动台试验加以修正。Abstract: The effect of hydrodynamic pressure should be considered in the seismic analysis of deep water bridges. The Morison equation is widely used to calculate the hydrodynamic pressure of bridge piers. It is evolved from the calculation formula of wave force. Its applicability to calculate the seismic hydrodynamic pressure has not been verified. There is also a lack of experimental research on the seismic hydrodynamic pressure of bridge piers. In this paper, a set of underwater shaking table test systems was designed. Shaking table tests with different cases were conducted on the bridge pier specimens of different sizes under sinusoidal excitation. The distribution law and changing law of the acceleration and hydrodynamic pressure of the piers were studied under different excitation amplitudes, excitation frequencies, section diameters and water depths. The experimental results of the hydrodynamic pressure and the calculated results by the Morison equation are compared to verify the applicability of the Morison equation under earthquake action. The results show that the influence of the excitation amplitude, excitation frequency, cross section diameter and water depth should be considered in calculating the acceleration and hydrodynamic pressure of piers under earthquakes. The Morison equation is not applicable to the calculation of hydrodynamic pressure of piers under earthquakes and should be modified based on many underwater shaking table tests.
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图 4 不同激励幅值下桥墩加速度变化规律
Figure 4. Change of acceleration of pier with different excitation amplitudes
图 5 不同激励频率下桥墩加速度变化规律
Figure 5. Change of acceleration of pier with different excitation frequencies
图 6 不同截面直径下桥墩加速度变化规律
Figure 6. Change of acceleration of pier with different section diameters
图 7 不同水深下桥墩加速度变化规律
Figure 7. Change of acceleration of pier with different water depths
图 8 不同激励幅值下桥墩动水压力变化规律
Figure 8. Change of hydrodynamic pressure of pier with different excitation amplitudes
图 9 不同激励频率下桥墩动水压力变化规律
Figure 9. Change of hydrodynamic pressure of pier with different excitation frequencies
图 10 不同截面直径下桥墩动水压力变化规律
Figure 10. Change of hydrodynamic pressure of pier with different section diameters
图 11 不同水深下桥墩动水压力变化规律
Figure 11. Change of hydrodynamic pressure of pier with different water depths
图 12 Morison方程计算结果与试验结果对比
Figure 12. Results of Morison equation compared with test results
表 1 正弦波激励频率和幅值
Table 1. Amplitude and frequency of sinusoidal wave
激励频率/Hz 激励幅值/g 1 0.1、0.2、0.4、0.7、1.0 2 0.1、0.2、0.4、0.7、1.0 4 0.1、0.2、0.4、0.7、1.0 7 0.1、0.2、0.4、0.7、1.0 10 0.1、0.2、0.4、0.7、1.0 
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