Design of Continuous Bridges Using Precast, Prestressed Concrete Girders Without End Blocks

This study investigated the feasibility of eliminating endblocks from pretensioned continuous bridge girders. The removal of endblocks is estimated to reduce girder costs by 5 to 10 percent. The girders studied were the Washington State Department of Transportation's "Series 14". These girders are characterized by 5 inch thick webs and are prestressed with both harped and straight 1/2 inch diameter grade 270 strands. Previous research had recommended the elimination of endblocks for simple span bridges. This study dealt with continuous bridges.

The research consisted of a field test and a destructive laboratory test. The field test was used to identify a bases for the destructive testing. A "Series 14" girder with endblocks and two "Series 60" girders without endblocks were instrumented with strain gages and monitored from the time they were manufactured to the time loads were tested on the bridge. The laboratory test was performed with a balanced cantilever arrangement using two 20-ft long "Series 14" girders without endblocks. The joint at the support was made continuous by the WSDOT. Concentrated loads were incrementally applied at a distance of 13 ft. 10 inches from the continuous support.

The modified girders performed effectively under the applied loads. Therefore, endblocks may be removed from continuous "Series 14" girders with normal diaphragms. The study recommends that one "Series 14" continuous girder without endblocks be designed and monitored through the various stages of constructions and service in another bridge.

Publication Date: 
Wednesday, September 30, 1987
Publication Number: 
WA-RD 155.1
Last modified: 
12/06/2017 - 14:22
Rafik Y. Itani, Girish S. Hiremath, Umesh Vasisth.
Washington State Transportation Center (TRAC), Washington (State). Dept. of Transportation.
Number of Pages: 
Blocks, Bridge design, Bridges, Continuous structures, Field tests, Girders, Laboratory tests, Mechanical tests, Monitoring, Precast concrete, Prestressed concrete, Strain gages, Structural design.