The International Information Center for Structural Engineers

Comparison of the Seismic Performance of Equivalent Straight and Curved Bridges due to Transverse Seismic Excitation

E. Khan,M.J. Kowalsky,J.M. Nau.
Book Title or Journal
15th World Conference on Earthquake Engineering
Number of pages
This study compares the transverse response of equivalent straight and curved bridges to investigate the hypothesis made by the AASHTO Guide Specification for LRFD Seismic Bridge Design that curved bridges may be analyzed as if they are straight, provided the bridge is regular. For this purpose curved bridges with subtended angles of 15, 30, 45, 60, 75, and 90 degrees, having the total arc length equal to the length of the equivalent straight bridge, are considered. Other parameters considered in this study are the number of spans (two, four and six), and abutment restraints (9 different conditions). The equivalent straight bridges are designed using the Direct Displacement Based Design (DDBD) procedure including these parameters. The resulting designs are then analyzed with Inelastic Time History Analysis using both straight and curved geometry. Each bridge was subjected to 7 spectrum compatible time histories. Individual as well as average results are tabulated. It is observed that deviation in the response of the curved bridge from the equivalent straight bridge increases as the subtended angles become larger and the number of spans reduces. It was also found that the type and degree of abutment restraint is a rather critical parameter in controlling the response of the bridge, the most significant being longitudinal abutment restraint which had a profound impact on results.
Direct Displacement Based Design,Bridges,Transverse Seismic Design of Curved Bridge