Investigation on generation mechanism of impact sound radiated from part of shoes of highway bridge and estimation of effectiveness of countermeasures for low-frequency sound

根据2005年9月中旬修正后的现场实测数据，分析了伸缩缝（或伸缩靴）位移与过桥车辆特性（车型、车速等）的关系。已经分析过了。然而，任何重要的关系都没有得到承认。这可能是由于车辆的重量无法准确获得，以及连续的车辆必然会引起复杂的振动。另一方面，基于数值分析，研究了调谐质量阻尼器（TMD）对公路钢桥低频声辐射的抑制效果。本文选取桥长约63米、桥宽约23米的三跨连续多主梁公路桥作为研究对象。这座桥目前正在使用中。桥梁的建模是基于使用三维 ...更多信息 从而使现场实测值与解析计算值之间的固有频率吻合较好。该桥上部结构共设置了12个调谐质量阻尼器。在数值分析中，采用了两轴四自由度的车辆模型。研究中考虑了单车过桥、两车并行过桥和两车连续过桥三种行驶模式。应用基于Newmark ′ s δ方法执行数值积分的有限元分析方法。声压级的计算方法是将桥面板各有限元表面辐射的声压相加。在该计算过程中可以考虑声音的干涉现象。结果表明，上部结构设置调谐质量阻尼器后，公路钢桥低频辐射声相对于一阶振型降低了3-4 dB，且受声位置与桥轴线垂直距离为31 m，与桥跨中心垂直距离为13 m。还已经揭示，对于二阶振动模式，预期约7分贝的降低。少

Based on the field measured data corrected in the middle of September, 2005, the relation between displacement of expansion joint (or shoe) and characteristics of vehicle passing over bridge (type of vehicle, velocity, etc.) has been analyzed. However, any significant relation has not been recognized. This may be depend on the fact that the weight of vehicle could not be obtained accurately and the consecutive vehicles must cause the complicated vibration. Then the modeling on behavior of expansion joint and shoe has not been successful at present.On the other hand, the effectiveness of tuned mass damper as countermeasure for low-frequency sound radiated from steel highway bridge has been investigated based on numerical analysis. The three span continuous multi main steel girder highway bridge whose bridge length and width are about 63 meters and 23 meters, respectively is selected as the subject of study. This bridge is currently under service. The bridge is modeled based by using 3-d … More imensional finite element method so as to obtain a good agreement of natural frequencies between field measured values and analytically calculated ones. Totally twelve pieces of tuned mass dampers are equipped with the superstructure of this bridge. In the numerical analysis, a vehicle model with two axles and four degrees of freedom is adopted. And three traveling patterns, that is, one vehicle, two parallel vehicles, and two successive vehicles passing over bridge are considered in this study. Finite element analysis method where numerical integral is executed based on Newmark's 8 method is applied. Sound pressure level is calculated by summing up the sound pressure radiated from the surface of each finite element of bridge deck. An interference phenomenon of sound can be considered in this calculation procedure. Sound receiving position is the point where a horizontal distance perpendicular to the bridge axis is 31 meters and a vertical one downward away from the center of bridge span is 13 meters.The results show that equipment of tuned mass dampers with superstructure leads to 3-4 decibels reduction of low-frequency sound radiated from steel highway bridge against first-order vibration mode. It has been also revealed that about 7 decibels reduction is expected against second-order vibration mode. Less