DISPLACEMENT–BASED SEISMIC DESIGN OF SKEW RC BRIDGE PIERS

Document Type : Original Article

Authors

1 Associate Professor, Department of Structural Engineering, Ain Shams University.

2 Associate Professor, College of Engineering , King Saud University, Saudi Arabia.

3 Professor, Department of Structural Engineering, Ain Shams University.

4 Structural Engineer, Dar Al-Handasah Consultants (Shair and Parteners), Giza, Egypt.

Abstract

Current bridge codes and standards apply ordinary bridge seismic design procedures
to skew bridges neglecting the torsional and bilateral effects during the seismic
excitations. As a result, there is a need to investigate the seismic behaviour of skew
bridge piers. This paper highlights the important features of displacement based
seismic design. Then, it provides the details and the results of a theoretical
parametric study to assess the seismic performance of skew bridge’s piers. The
theoretical study parameters are the skew angle, the pier height to thickness ratio,
and the vertical reinforcement ratio. A commercial nonlinear finite element software
package, Strand 7, was used in the analysis. A force controlled pushover analysis
with triangular load pattern was applied to push pier models. The performance
relationships of secant stiffness, length of the formed plastic hinge, and displacement
ductility to pier geometry, and vertical reinforcement ratio were developed for skew
bridge’s piers. Results show that displacement ductility for skewed piers is very
sensitive to the variation of the skew angle at low skew angles especially for low
vertical reinforcement ratio. Further, the displacement ductility is reduced as the
amount of vertical reinforcement increased with the confining reinforcement ratio
being constant. It was also shown that the effect of skew angle becomes less
significant for small skew angles and for short piers. Finally, the secant stiffness
changed significantly with skew angle variation for short piers.

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