Vibration damping for rapid transit elevated structures

Abstract

It is well known that train operations on an elevated structure are much noisier than those on a grade level roadbed. For the composite type of bridge structure made up of a concrete deck on a steel box girder, theoretical and experimental studies show that the steel web plates are a major source of noise radiated from the structure. This paper will summarize some of the work done over the last 15 years to reduce this source of noise by damping the steel box girder of such structures. Both homogeneous type damping and shear type, or constrained layer damping materials have been used successfully. The noise reduction on one type of structure with homogeneous damping mateddais will be described, including scale model and full scale tests. In another type of structure, a partial damping treatment with shear type damping material was developed to reduce the very disturbing low frequency noise radiated by the steel box girder plates. Full scale field tests will be described in which noise and vibration measurements were made on damped and undamped sections of the elevated structure during train passage at several speeds. The effect of damping on the noise and vibration levels will be detailed.