An application of spectral techniques
To inelastic seismic response predictions
Techniques of seismic load prediction using response spectra have been in general used for many years and the normal mode-response spectrum approach forms the background to a majority of modern earthquake resistant design codes. It is widely appreciated that in the general case of multi-degree of freedom systems, extension of the approach to the prediction of structural response in the post-elastic range is invalid. Consequently analyses based on the system, using a time history of ground acceleration as the excitation, have been developed.
However, some structures may be modelled reasonably accurately by a single degree of freedom system and in these circumstances spectral techniques may be applied justifiably to post-elastic seismic response calculations.
Predictions of the post-elastic response of a viaduct pier, making use of earthquake response spectra, are described in this paper.
A simple method involving consideration of conservation of energy and a second approach based on the reserve energy technique are reviewed and the behaviour predicted by applying each to the proposed pier is compared with the response determined from a computer analysis involving numerical integration of the equations of motion of the system.
It is shown that in the case of the particular structure examined the results of the spectral technique considerations are of the same order as those obtained from more complex analyses, thereby supporting the contention that, at least for some structures, estimates of post-elastic seismic behaviour based on response spectra applications may be of value, particularly at the initial design stage when a full computer based analysis may not be warranted.
McConnel, R. E., "Seismic Response of a Proposed Railway Viaduct", thesis presented to the University of Canterbury in 1970 in partial fulfillment of the requirements for the degree of Blaster of Engineering,,
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Blume, J. A., Newmark, N. M. and Corning, L. H. "Design of Multistory Reinforced Concrete Buildings for Earthquake Motions" Portland Cement Association, Chicago, U.S.A., 1961.
Blume, J. A., "A Reserve Energy Technique for the Earthquake Design and Rating of Structures in the Inelastic Range" Proceedings 2nd W.C.E.E., Tokyo, 1960.
Veletsos, A. S. and Newmark, N. M. "Effect of Inelastic Behaviour on the Response of Simple Systems to Earthquake Motions" Proceedings 2nd W.C.E.E., Tokyo, 1960.
Copyright (c) 1970 R. Shepherd, R. E. McConnel
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