Experimental noise and vibration characteristics of elevated urban rail transit considering the effect of track structures and noise barriers.

Vibration of the elevated urban rail transit (URT) severely affects the health of nearby residents, threatens the integrity of adjacent historic buildings, and aggravates the performance of vibration-sensitive instruments in buildings, and the accompanied annoying structure-borne noise always arouses public complaint. Vibration and noise mitigation measures through track structures and/or noise barriers are increasingly favored to deal with these challenging issues. This paper presents systematic field measurements on noise and vibrations of elevated URT. The vibration experiment covers vibration of track structures, bridge girders and piers, and ground soil under three different track structures, i.e., embedded sleeper track, ladder sleeper track, and floating slab track (FST) with rubber mats. Noise measurements were also conducted considered the effect of track structures and with or without fully enclosed noise barriers. It is shown that ladder sleeper track and FST were more effective in control bridge vibration than ground vibration. The overall vibration level of the bridge is 8~10 dB greater than the ground vibrations. The noise reduction effect through track structure was limited for far-field ground. Furthermore, it is found that the noise barrier was more effective to reduce near-field wheel/rail rolling noise rather than far-field noise. Good correlation between structure-borne noise and vibration was observed for both the embedded sleeper track and FST at the bottom slab of the box girder bridge.