Abstract
Bridge design spectra in the current design specifications are geometric mean based. In other words, the underlying research on which ground motion data are based predicts the geometric mean spectral acceleration of two horizontal components. This is, perhaps, transparent to many engineers performing bridge design in regions subject to extreme seismic loading. For response spectrum analyses, this does prove problematic when estimating structural response to bidirectional ground motions. Prevailing combination rules rely on the assumption that, when one component produces the maximum structural response, the second component produces 30% of the corresponding maximum. The purpose of this paper is to assess the validity of this prevalent rule for sites characterized by large magnitude earthquakes (MW = ±7.7) and Site Class D/E subsurface conditions. This study further provides estimates of maximum-to-geometric mean displacement ratios for various levels of ductility and provides estimates of dispersion for inelastic displacements.
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Published In
Practice Periodical on Structural Design and Construction
Volume 22 • Issue 1 • February 2017
Copyright
© 2016 American Society of Civil Engineers.
History
Received: Jun 7, 2016
Accepted: Jul 12, 2016
Published online: Aug 25, 2016
Discussion open until: Jan 25, 2017
Published in print: Feb 1, 2017
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