A numerical procedure was proposed to simulate the time, the frequency and the space characteristics of concrete bridge-borne low-frequency noises under moving trains. The finite element method and the mode superposition method were used to solve the transient dynamic train-track-bridge interaction problem with emphasis on local bridge vibration of high frequency. The boundary element method was applied to find the modal acoustic transfer vectors. The bridge-borne sound pressure spectra for various field points were then computed through multiplying the modal acoustic transfer vectors by the modal coordinate spectra of the bridge. The time-domain sound pressures were finally obtained with the help of the inverse fast Fourier transforms. Vibration and noise field tests were carried out with a real urban rail transit U-shaped prestressed concrete girder in Shanghai. The vibration accelerations at various parts of the bridge and the bridge-borne sound pressures at different field points were computed and compared with the measured data. It is found that the computed results agree well with the measured ones in terms of both time-history and spectrum.%提出一种列车激振下混凝土桥梁低频结构噪声数值预测方法,以获取结构噪声时间、频率及空间特性.采用有限元法和模态叠加法求解列车-轨道-桥梁动力相互作用系统瞬态响应,重点关注桥梁高频局部振动.采用边界元法求解桥梁模态声传递向量,将其与桥梁模态坐标频谱相乘得到空间各场点声压频谱,再对声压频谱进行快速傅里叶逆变换获得相应声压时程.以上海轨道交通预应力混凝土U形梁为例,进行振动与噪声现场实测,将桥梁不同部位局部振动加速度和不同场点声压测试数据与数值模拟结果进行比较.结果表明:模拟和测试结果在时程曲线及频谱曲线上均吻合较好.
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