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

2006 Fiscal Year Final Research Report Summary

• Project/Area Number: 17560422
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Structural engineering/Earthquake engineering/Maintenance management engineering
• Research Institution: University of Yamanashi
• Principal Investigator: SUGIYAMA Toshiyuki University of Yamanashi, Interdisciplinary Graduate School of Medicine and Engineering, Professor, 大学院医学工学総合研究部, 教授 (50143954)
• Project Period (FY): 2005 – 2006
• Keywords: low-frequency noise / highway bridge / bridge vibration / expansion joint / shoe

Research Abstract

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 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.