Mechanism, annoyance and control of noises generated from modular expansion joint in highway bridges

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The objective of this research is to investigate the mechanism, annoyance and control of environmental noises generated by vehicle passage through modular type expansion joint in highway bridges. The research results are summarized as follows.1. The mechanism and control of noise generation for modular expansion joints were investigated in experiments on a full-scale model of the joint. Noise and vibration of the joint model were measured when a car was running over the model. It was concluded, based on this measurement together with tests of the acoustic and dynamic characteristics of the joint model, that the noise from the top of the joint could be attributed to a sudden change in the air pressure in the gaps formed by the sealing rubber elements, and the noise from the bottom was probably caused by sound radiation from vibration of the middle beams. Effects of some proposed noise control measures were also investigated experimentally.2. Field measurements of noise and vibration were conducted in a non-composite I-shaped steel-girder bridge and in a PC box girder bridge with modular expansion joints. In each case, the noise was measured at several points above and below the bridge when different type of vehicles passed over the joint with different speeds. The non-stationary characteristics of noise propagation in the field and effects of bridge, vehicle, and joint types were clarified. Possible sources of environmental noise problem were also discussed by studying the A-filtered spectra of sound pressures and their non-stationary characteristics.3. The annoyance of field-measured noises of modular type joint was also investigated by psychoacoustic experiment in a laboratory in order to identify the annoying noise components.