Inelastic Displacement Spectra for Bridges Using the Substitute-Structure Method
Publication: Practice Periodical on Structural Design and Construction
Volume 21, Issue 2
Abstract
The design of bridge structures for seismic loading by displacement-based procedures has become preferred over force-based procedures in modern specifications. One key step in displacement-based design (DBD) is the estimation of inelastic displacement. Current AASHTO specifications rely on a linear response spectrum analysis with an amplification factor, Rd, for conventionally designed bridges and on the substitute structure method (SSM) for analysis of isolated bridges to estimate inelastic displacements. Both methods are used in this study for a selected site and target acceleration response spectrum. The procedures for both are outlined in detail. Displacement spectra from nonlinear response history analyses (NLRHA) are generated for seven ground-motion sets and compared to results from the two simplified methods. The SSM is shown to produce inelastic displacement estimates that more closely match NLRHA results than do results from the AASHTO Rd method over a wide range of periods for the specific conditions of (1) a large modal magnitude earthquake, (2) a class D subsurface profile, (3) accelerations characteristic of the selected site, and (4) reduced initial damping to mimic tangent-stiffness-damping.
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Published In
Practice Periodical on Structural Design and Construction
Volume 21 • Issue 2 • May 2016
Copyright
© 2015 American Society of Civil Engineers.
History
Received: Jun 8, 2015
Accepted: Oct 13, 2015
Published online: Dec 30, 2015
Published in print: May 1, 2016
Discussion open until: May 30, 2016
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