Report No.: CCEER-99-5

Title: Restrainer Design Procedures For Multi-Span Simply-Supported Bridges

Authors: M. Randall, M. Saiidi, E. Maragakis and T. Isakovic

Date: April 1999

Sponsoring Agency:
Multidisciplinary Center for Earthquake Engineering Research (MCEER)
State University of New York at Buffalo

Performing Organization:
Department of Civil Engineering/258
University of Nevada, Reno
Reno, NV 89557


The 1971 San Fernando Earthquake in California caused highway bridges to collapse because of excessive longitudinal movement at expansion joints and supports. Since then, the California Department of Transportation (Caltrans) has installed longitudinal cable restrainers to prevent such collapse. In the study presented in this report, two existing design methods, the Caltrans and AASHTO methods, were evaluated for simply-supported bridges. In addition, three new design methods for restrainers were proposed and evaluated. The adequacy of the design methods was determined using nonlinear response history analyses of a large number of two- and five-span bridges. The models represented highway bridges that would be retrofitted with restrainers. All of the procedures considered in this study were found to be effective in preventing spans from unseating in most bridges even under strong earthquakes. In the most critical cases with narrow supports and skew, however, it was found that the Caltrans and a modified version of the Caltrans methods (a new method developed in this study) were the only procedures that prevented unseating.