Testing bridge structure vibration using a similarity model

Bridge structures, which account for a large proportion of high-speed railways and urban rail transits, produce vibration that radiate low-frequency structural noise. This low-frequency noise can affect people’s physical and mental health, as well as affect ancient buildings along the line; the manufacture of precision instruments and equipment; and the use of high-precision laboratories.

The authors of new paper in the Journal of Aerospace Engineering, “Design, Verification, and Test of the Bridge Structure Vibration Similarity Model” by Xiaoyan Lei, Zhenguo Wang, and Kun Luo, designed and manufactured a 32 meter simply supported box girder bridge model to study the vibration characteristics of bridge structures caused by rail transit. Read their findings, analyzing the mechanism and control measures of vibration and the noise of bridge structures in the ASCE Library.

Abstract

At present, the method of model testing is rarely used to study the low-frequency vibration problems of bridge structures, because it is difficult to keep the similarity between the bridge model and the prototype in model testing. Based on the similarity law of elastic force, a similarity model of a 32-m simply supported box girder bridge, a model bridge with a geometric similarity ratio of 10∶1, was designed and manufactured in this paper. The validity of the similarity model was verified by modal testing and numerical simulation. Then, through the hammer test of the similarity model, the vibration transmission characteristics of the model box girder between the panels and along the longitudinal direction of the bridge were studied. Also, the influence of the bridge support on the box girder vibration and the vibration reduction effect of the bridge support were analyzed. The results showed that when the top plate of the box girder is excited, the vibration attenuation from the top plate to the bottom plate is the fastest, followed by the top plate to the web, and from the top plate to the wing plate is the slowest. In the frequency range of less than 45 Hz, the vibration of the top plate attenuates slowly along the longitudinal direction of the bridge; in the frequency range of 45–200 Hz, the vibration of the top plate attenuates rapidly from the middle span to the 1/4 span section of the bridge and attenuates slowly from the 1/4 span to the support section of the bridge. The vibration reduction effect of the elastic support on the bridge pier was related to support stiffness and vibration frequency; the general rule was that the smaller the support stiffness, the better the vibration reduction effect. In addition, the vibration reduction effect varied greatly with different vibration frequencies.

Read the full paper in the ASCE Library: https://doi.org/10.1061/(ASCE)AS.1943-5525.0001221

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