A Study on the Generating Mechanism of Elevated Structure Noise and Its Countermeasures

高架结构噪声是近年来在高架高速公路周围出现的高架结构噪声问题，它是指高架高速公路结构单元在音频范围内辐射的噪声。1.工字钢梁声辐射的模型分析：采用简化模型分析工字钢腹板的声辐射特性。在模型分析中，梁被模拟为无限长的弹性板条。并将计算结果与实际高架结构噪声的计算结果进行了对比分析，以揭示高架结构噪声产生的主要原因。工字钢振动的边界元分析：为了进一步探讨噪声产生的主要原因，利用Bound…软件对某钢工字梁的振动进行了分析更多元单元方法(BEM)。根据上述边界元结果，详细讨论了高架结构噪声与梁的结构之间的关系。作为模型分析的结果，无限长弹性板条的辐射噪声与高架结构的噪声具有非常相似的特征。这可以被解释为钢工字梁可能是高架结构噪声的主要原因。边界元分析结果表明，在500赫兹附近，腹板的横向振动占主导地位，而当腹板受到接近面内力的激励时，横向振动仍占主导地位。这些结果表明，工字钢腹板与高架结构噪声有很强的相关性。结果表明，高架结构噪声的主要原因是工字钢腹板。虽然仍有一些问题需要解决，例如梁的实际激励条件，但上述结果可以为高架结构噪声问题的对策提供基本思路。较少

The problems with the elevated structure noise, which is the noise in audio-frequency range radiated from the structural elements of the elevated motorway, recently arises around the elevated motorways. To investigate the mechanism of the generation of, and to establish the countermeasure to the elevated structure noise, the following considerations were carried out :1. Model analysis of the acoustic radiation of steel I-beams : The sound radiation characteristics of web plate of steel I-beams were analyzed using a simplified model. The beam was modelled a baffled strip of elastic plate of infinite length in the model analysis. The features of the calculated results were discussed in comparison with those of those of the actual elevated structure noise in order to shed some light on the main cause of the noise.2. Boundary element analysis of the vibration of steel I-beams : To make a further investigation on the main cause of the noise, vibration of a steel I-beam was analyzed by bound … More ary element method (BEM). The relationship between the elevated structure noise and the structure of the beam was discussed in detail from the above BEM results.As the results from the model analysis, the radiated sound from an elastic plate strip of infinite length was found to have very similar features to the elevated structure noise. This can be interpreted to imply that steel I-beams can possibly be the main cause of the elevated structure noise. The results of the BEM analysis show that the transverse vibration, which may be the most responsible to sound radiation, is dominant in the web plate around 500Hz, and it is still dominant when the web is excited by a nearly in-plane force. These results suggest that the web plate of steel I-beams is strongly relevant to the elevated structure noise. From the above results, it can be concluded that the main cause of the elevated structure noise is the web plate of steel I-beams. Though there is still some problems to be solved, which include the actual excitation condition of the beam, for example, the above results can help with basic ideas for countermeasures to the elevated structure noise problems. Less