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

高架结构噪声是指高速公路结构构件辐射出的音频范围内的噪声，是近年来围绕高架公路产生的噪声问题。为探讨高架结构噪声的产生机理，建立高架结构噪声的防治对策，本文主要从以下几个方面进行了探讨：1、高架结构噪声的产生机理；钢工字梁声辐射模型分析：采用简化模型分析了钢工字梁腹板的声辐射特性。在模型分析中，将梁建模为无限长弹性板的折流板条。分析了计算结果的特点，并与实际高架结构噪声的计算结果进行了比较，以期对产生噪声的主要原因有所了解。工字钢梁振动的边界元分析：为了进一步研究产生噪声的主要原因，采用边界元法（BEM）对工字钢梁进行了振动分析。根据上述边界元计算结果，详细讨论了高架结构噪声与梁结构的关系。模型分析结果表明，无限长弹性板带的辐射声与高架结构噪声具有非常相似的特征。这可以解释为，工字钢梁可能是高架结构噪声的主要原因。边界元分析结果表明，500Hz左右腹板的横向振动可能是声辐射的主要原因，当腹板受到近面内力的激励时，横向振动仍然占主导地位。这些结果表明，工字钢腹板与高架结构噪声密切相关。从以上结果可以得出，高架结构噪声的主要原因是工字钢腹板。虽然还存在一些问题需要解决，例如梁的实际激励条件，但以上结果可以为高架结构噪声问题的对策提供基本思路。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