Comparison of field measured data of low-frequency noise radiated from steel bridges with analytical ones and its reduction countermeasure

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As the numerically calculated values of sound pressure level radiated from 3-span continuous steel girder bridge which locates on Chugoku Express Highway agree well with the field measured data, the appropriateness of analytical method developed by the head investigator's research group has been proved.By Use of the analytical method developed here, the effectiveness of several types of reduction countermeasure against low-frequency sound radiated from 3-span continuous steel girder bridge has been investigated. The following results have been obtained. That is,(1) The method in which end sway bracing is covered by concrete is not so effective to reduce the low-frequency sound pressure level.(2) The effectiveness of both sponson beam type bridge and sponson deck type bridge depends on the span length of bridge and the traveling velocity of vehicle passing over bridge.(3) The effectiveness of both sponson beam type bridge and sponson deck type bridge also depends on the supporting condition with respect to sponson part.(4) The method that central point of each span is supported with fix shoe and/or pin shoe is considerably effective although its cost becomes higher.(5) Low-frequency sound pressure level radiated from bridges is sensitive to the condition whether vehicle passing over bridge vibrates or not when it enters into the bridge. This fact means that careful attention should be paid to the numerical analysis.A numerical analysis about the effect of spring constant of vehicle passing over bridge on the low-frequency sound pressure level radiated from highway bridge will be carried out in the near future.