METALLIC DAMPERS FOR SEISMIC DESIGN AND RETROFIT OF BRIDGES
Author: Chen, G Mu, H Bothe, E R | Size: 6.34 MB | Format: PDF | Quality: Original preprint | Publisher: University of Missouri, Rolla | Year: 2001 | pages: 146
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A practical bearing scheme is proposed in this study, consisting of expansion rocker bearings and steel rods (metallic dampers). It can accommodate seismic effects while it allows for free thermal expansion. Tests of metallic dampers have shown that dampers of straight rods can contribute over 10% damping at the small-to-medium displacement range. Extensive tests on a 1/10-scale bridge model indicated that metallic dampers can also significantly reduce the dynamic responses of the bridge by isolating vibration propagating from the substructure to the superstructure. High rocker bearings provided considerable damping to the bridge-damper system by dissipating energy along the friction surface between pin and web of the bearings. They remain stable even at the peak ground acceleration of 0.54g at resonance. To account for pounding effect at the expansion joints of bridges, design equations for determining the equivalent viscous damping corresponding to various sizes of bridge joints were developed. Integrating the equivalent damping into the response spectrum analysis procedure allows engineers to analyze the bridges with pounding effect in a linear fashion.
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METALLIC DAMPERS FOR SEISMIC DESIGN AND RETROFIT OF BRIDGES
Author: BY: Genda Chen, Ph.D., P.E. Huimin Mu, Ph. D. Candidate Eric R. Bothe, EIT | Size: 3.5 MB | Format: PDF | Quality: Unspecified | Publisher: University Transportation Center at the University of Missouri-Rolla JEFFERSON CITY, MISSOURI DATE SUBMITTED: May, 2001 | Year: 2001 | pages: 144
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The purpose of this study was to develop an economic solution for the design and retrofit of continuous steel girder bridges in low occurrence seismic zones such as the Central and Eastern United States. Prior to 1975, the construction of such bridges exclusively used high rocker bearings and included two expansion joints at the ends of bridge decks for thermal expansion and contraction. They were designed with no seismic considerations. In this report, metallic dampers (steel rods) are introduced between the substructure and superstructure to improve the seismic performance of the bridges. Metallic dampers are used to provide restraint to the longitudinal movement of the bridges’ superstructure under non-seismic loads and yield as fuse-like elements during a strong earthquake event. The scope of work included optimization of metallic dampers, experimental study of the cyclic behavior of full-scale dampers, experimental study of the dynamic behavior of high rocker bearings and dampers installed in a small-scale bridge system, and analytical development of a simplified procedure to account for pounding
effect in the response spectrum analysis of highway bridges.
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