铁路32m混凝土简支箱梁结构噪声试验研究

Experimental Study on Structure-Borne Noise of Railway 32m Simply-Supported Concrete Box-Girder

以32m单线和双线单室混凝土简支箱梁为对象,通过噪声试验、结构有限元和声学有限元分析,研究箱梁结构噪声的声辐射特性、峰值频率产生的原因及评价方法。结果表明:列车通过桥梁时,离箱梁表面较远处的噪声级起伏不大,可采用稳态算法简化分析;混凝土箱梁的结构噪声主要分布在250Hz以下,且随频率的增加而迅速衰减,因此理论预测时可将250Hz作为截止频率;单线和双线箱梁的2个噪声峰值频率分别为63和160Hz,以及50和315Hz,二者均在第1个峰值频率处达到最大声压级,且此峰值频率处的噪声具有明显的有调性;不同箱室尺寸箱梁的结构噪声声辐射差异较大,车速并不是噪声的第一决定因素;混凝土箱梁结构噪声的峰值频率出现在声辐射效率和振动响应均较大处,因此应避免结构振动模态和空腔声学模态重合而导致空腔共鸣引起的噪声被放大;建议修订铁路噪声相关规范时,考虑混凝土箱梁低频结构噪声的危害。

Based on the study objects of single- and double-track simply-supported concrete box-girders with only one cell and a span of 32 m, this paper investigated the sound radiation characteristics of struc- ture-borne noise, reasons leading to peak frequency and evaluation methods by field measurements, struc- tural and acoustical finite element analysis. The results show that. during a train runs across bridge, the noise far away from the box-girder surface fluctuates slightly, which means that simplified steady-state a- coustic analysis is feasible; structure-borne noise from concrete box-girder dominates in the frequency low- er than 250 Hz and decreases rapidly with increasing frequency, accordingly, 250 Hz can be regarded as the upper limiting frequency for theoretical prediction; the two frequencies of peak noise of single- and double- track box-girder are 63 and 160 Hz, as well as 50 and 315 Hz, respectively, and the noise reaches maxi- mum in the first frequency where the tonal noise characteristics occur; the sound radiation characteristics change greatly with different structural dimensions of box-girders and train speed is not the first key influ- ence factors; the peak noise frequency of structure-borne noise from box-girder is higher when the sound radiation efficiency and vibration response are simultaneously higher, therefore, the coincidence of struc- ture vibration mode and cavity acoustic mode should be avoided for the occurrence of cavity resonance phe- nomenon what may amplify the noise; due consideration is proposed to be considered on low-frequency noise from concrete box-girder when revising relevant railway noise specifications.