基于波面分解的跨海桥梁下部结构波浪荷载计算方法

Calculation Method of Wave Loadings on Sea-crossing Bridge Substructures Based on Decomposition of Wave Elevation

为建立波面与结构波浪荷载之间的直接联系,提出一种基于波面分解的桥梁下部结构波浪荷载计算方法。通过傅里叶变换将波面时程分解为有限个线性规则波的叠加,根据线性波浪理论,将每个规则波的水质点速度、加速度组合叠加,得到波面对应的水质点速度和加速度分布,最后利用Morison方程计算波浪荷载。通过与既有波浪理论、水槽试验和数值模拟结果进行对比,验证了方法的有效性和准确性。研究结果表明:(1)当波高不大时,本文方法得到的水平速度和加速度与波浪理论值吻合良好;(2)基于水槽试验的波面分解,本文方法结果与流速仪实测结果在时域与频域均吻合良好;(3)以一个圆柱桥墩为例,本文方法比数值模拟计算效率高,墩底剪力、弯矩的误差分别为3%、8%左右。

In order to establish the relationship between wave elevation and wave loading, a calculation method of wave loadings on bridge substructures is developed based on the decomposition of wave elevation. Wave elevation is firstly decomposed into the superposition of a finite number of linear regular waves by Fourier transformation. The velocity and acceleration of water particle of each regular wave are superimposed according to the linear wave theory. The wave kinematics, such as water particle velocity and acceleration corresponding to the wave elevation, are then obtained. Finally, the wave loadings are calculated with Morison equation. The efficiency and accuracy of the developed method are validated by means of wave theory, wave flume experiment and numerical simulation. Study results show that, 1) the horizontal velocity and acceleration obtained by the developed method agree well with those of wave theory for waves with low wave height;2) based on the decomposition of wave elevation in wave flume experiment, the results calculated by the developed method coincide with those from current meter in both time domain and frequency domain;3) in the case of a cylinder pier, the developed method is more efficient than the numerical simulation, and the error of the base shear and bending moment is 3% and 8% respectively.