Box Girder Bar and Bracket Seismic Retrofit Devices


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Title: Box Girder Bar and Bracket Seismic Retrofit Devices

Author(s): L. G. Selna, L. J. Malvar, and R. J. Zelinski

Publication: Structural Journal

Volume: 86

Issue: 5

Appears on pages(s): 532-540

Keywords: box beams; bridge decks; control joints; earthquake-resistant structures; girder bridges; high-strength concretes; repairs; restraints; slabs; tests; Structural Research

Date: 9/1/1989

After the 1971 San Fernando earthquake, the California Department of Transportation adopted a bridge strengthening, or retrofit, program. Many of the collapses that occurred were attributed to loss of vertical support at the expansion joints, so the retrofit program focused on strengthening of the bridge structure at these locations. Several types of devices were developed. Two of the devices used were: 1) the bar restrainer that links the hinge-joint diaphragms together, and 2) the deck-slab bracket restrainer that anchors cables to join the underside of deck slabs on opposite sides of the joint. This paper is concerned with determination of strength, stiffness, and cyclic load-deflection behavior of bridges that have been retrofit with bar or deck-slab bracket restrainers. The properties were evaluated as part of a full-scale experimental test program conducted at UCLA. The test results show that the bar restrainer experiences a ductile load-deflection behavior while the bars undergo yield. The load-deflection relation of the bracket device is influenced by cable behavior and the strength is limited by the reinforced concrete.