Environmental noise beside an elevated box girder bridge for urban rail transit

Abstract

Noise generated by trains running on elevated lines creates many disturbances to the normal lives of surrounding residents. Investigations have shown that people living along elevated lines complain that the noise is sometimes unbearable. To better control the noise and optimize the acoustic environment, noise spectrum characteristics were analyzed and compared with a field test and a numerical simulation. Through an energy analysis of the noise on the bridge side, the energy distribution characteristics of the noise at specific measuring points in different frequency bands were obtained. The influence of the Doppler effect on frequency shift was analyzed. Based on the partial coherence theory, a multi-input and single-output program was compiled to calculate the correlation and contribution degree of the bridge structure-borne noise and wheel/rail noise at the one-third octave center frequency. The results show that the peak noises of the bridge and the wheel/rail are concentrated at 31.5`-63 Hz and 400`-800 Hz, respectively. For environmental noise on the bridge side, the frequency band above 250 Hz is mainly affected by the wheel/rail noise. In areas of noise source strength, the relative ratio of noise energy above 250 Hz can reach 83.4%. Noise in the near ground and far bridge area is mainly low-frequency, and the relative energy ratio is about 8.9%. The Doppler effect has an influence of less than 6% on the frequency shift with a speed of 67.9 km/h. In the low-frequency band below 250 Hz, the noise in the acoustic shadow area near the bridge and the ground is mainly contributed to by the vibration-radiated noise of the bridge, of which the contribution of the bottom panel is the most prominent. The noise in the comprehensive noise area of the far bridge is mainly caused by the structure-borne noise of the bridge, and the contribution of each bridge panel is different. This study can provide a reference for finding the source of elevated rail noise in some challenging frequency ranges and for then determining optimal designs and measures for noise reduction.

抽象

目的

为了更好地控制高架轨道交通噪声、优化声环境, 本文对噪声源强度和环境噪声的频谱特性和分频段能量进行分析,并将现场试验和数值模拟进行对比研究, 希望能在特定敏感频率下寻找高架轨道噪声源, 进而为实现高架线路的降噪优化设计提供参考。

创新点

1. 完成了可靠的基于车-线-桥耦合动力学的桥梁结构环境声学预测模型的搭建及应用;2. 考虑了多普勒效应对实验结果的影响, 并以此得到了修正的相干分析结果。

方法

1. 基于高架地铁线路的现场试验, 以普通板式轨道为研究对象, 采用时域、频域和三分之一倍频程分析方法对箱梁桥侧环境噪声的传播和衰减进行分析;2. 基于地铁车-线-桥耦合动力学方法及有限元、边界元方法建立声辐射计算模型, 并在此基础上计算箱梁结构对环境噪声的影响以及不同面板对应的声学特性;3. 考虑多普勒效应对频移的影响, 并基于偏相干理论编制多输入单输出计算程序, 计算桥梁结构噪声与轮轨噪声的相关性和贡献程度。

结论

1. 该桥和轮轨的峰值噪声分别为31.5~63 Hz和400~800 Hz;在桥侧环境噪声中, 250 Hz以上频段主要受轮轨噪声的影响;在噪声源强度范围内, 250 Hz以上噪声相对能量比可达72.8%;近地面远桥区噪声以低频为主, 其相对能量比约为8.85%。2. 速度为67.9 km/h时, 多普勒效应对频移的影响小于6%;在250 Hz以下的低频段, 桥梁附近和地面声阴影区的噪声来自桥梁振动辐射噪声, 其中底板的贡献最大;远桥综合噪声区的噪声主要由桥梁结构传声引起, 且各板结构的贡献度不同。