Displacement-based design of continuous concrete bridges under transverse seismic excitation

Student: Juan Camilo Alvarez Botero
Supervisor: Prof. M.J.N. Priestley

Abstract

In this work a displacement-based design procedure for multi-span reinforced concrete bridge structures then subjected to seismic action in the transverse direction is presented. The procedure, initially proposed by Priestley [Priestley, 1993], is reviewed and some improvements are implemented. The design methodology is then applied to different possible bridge configurations, resulting in 28 main different designs. The accuracy of the method in terms of reaching the target displacements under the design earthquake level is then assessed using inelastic time-history analysis. Discussion of the appropriate level of damping to be considered in the inelastic time-history analysis of this type of structures is provided; with bases on parallel research being carried out at the ROSE School on equivalent damping for displacement-based design applications, [Grant and Priestley, 2004]. Dynamic amplification of the deck transverse moments is investigated and compared with analytical results using different variations of the modal superposition approach. What has been called the "Modified Modal Superposition", first introduced for cantilever walls, [Priestley, 2003], is then proposed as an effective method to account for higher mode effects on the deck transverse moment distributions. Finally some parametric analyses are presented to provide an idea of the scope and applicability of the design procedure under different conditions to those assumed for the initial designs.

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