Effective Stiffness and Equivalent Damping of Base‐Isolated Bridges
Publication: Journal of Structural Engineering
Volume 119, Issue 10
Abstract
In this paper, the guide specifications for bridge base isolation published in 1991 by the American Association of State Highway Transportation Officials (AASHTO) are briefly summarized and discussed. The effective stiffness and equivalent damping ratio given in the AASHTO isolation specifications are evaluated. Based on this study, it is concluded that the equivalent damping ratio determined using the AASHTO procedure may decrease with respect to the increase of the inelastic deformation of lead‐rubber bearings. In addition, the equivalent damping ratios calculated for a single‐degree‐of‐freedom system subjected to a generated AASHTO design earthquake may be larger than 30% for a wide fundamental period range. As a result, a three‐dimensional inelastic time‐history analysis as required by the AASHTO provisions may be necessary. However, to require a three‐dimensional inelastic time‐history analysis could be a dilemma for the current bridge engineering design practice. As an alternate approach, an empirical method is proposed for the determination of the effective period shift and equivalent damping ratio.
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References
1.
AASHTO design procedures for seismically isolated bridges. (1992). Dynamic Isolation Systems, Inc., Berkeley, Calif.
2.
“Design of lead‐rubber bridge bearings.” (1983). Civil division publication 818/A, New Zealand Ministry of Works and Development, Wellington, New Zealand.
3.
Guide specifications for seismic isolation design. (1991). American Association of State Highway and Transportation Officials, Washington, D.C.
4.
Iwan, W. D. (1980). “Estimating inelastic response spectra from elastic spectra.” Earthquake Engrg. and Struct. Dyn., 8, 375–388.
5.
Iwan, W. D., and Gates, N. C. (1979). “The effective period and damping of A class of hysteretic structures.” Earthquake Engrg. and Struct. Dyn., 7, 199–211.
6.
Mahin, S. A., and Lin, J. (1983). “Construction of inelastic response spectra for single‐degree‐of‐freedom systems,” Rep. No. UCB/EERC‐83/17, Earthquake Engineering Research Center, Univ. of California, Berkeley, Calif.
7.
Mayes, R. L., Buckle, I. G., Kelly, T. E., and Jones, L. R. (1992). “AASHTO seismic isolation design requirements for highway bridges.” J. Struct. Engrg., ASCE, 118(1), 284–304.
8.
Uniform building code. (1991). International Conference of Building Officials, Whittier, Calif.
Information & Authors
Information
Published In
Journal of Structural Engineering
Volume 119 • Issue 10 • October 1993
Pages: 3094 - 3101
Copyright
Copyright © 1993 American Society of Civil Engineers.
History
Received: Jun 10, 1992
Published online: Oct 1, 1993
Published in print: Oct 1993
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