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月中旬修正的现场实测数据，分析了伸缩节(或伸缩鞋)位移与过桥车辆特性(车型、车速等)之间的关系。已经分析过了。然而，任何重大的联系都没有被认识到。这可能是由于车辆的重量无法准确获取，连续行驶的车辆必然会引起复杂的振动。另一方面，在数值分析的基础上，研究了调谐质量阻尼器对公路钢桥低频辐射噪声的抑制效果。选取长约63m、宽约23m的三跨连续多主钢梁公路桥作为研究对象。这座桥目前正在使用中。利用三维…对该桥进行建模。更多维的有限元方法，以获得与现场实测值和解析计算值之间的固有频率很好的一致性。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，采用两轴四自由度的车辆模型。研究中考虑了三种通行模式，即一辆车、两辆平行车和两辆连续车过桥。采用基于Newmark方法的数值积分的有限元分析方法。将桥面各单元表面辐射的声压相加，即可计算出桥面的声压级。在此计算过程中可以考虑声音的干扰现象。声接收位置为垂直于桥梁轴线的水平距离为31m，距桥跨中心向下的垂直距离为13m的位置。结果表明，上部结构调谐质量阻尼器的设置使公路钢桥辐射的低频噪声相对于一阶振型降低了3~4分贝。研究还表明，与二阶振动模式相比，预计可降低约7分贝。较少

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