Stress on simply supported bridge girders made continuous by full post-tensioning under static load

Abstract

Simple-span precast prestressed girders can achieve continuity, which in turn eliminates deck joints and protects the reinforcement from corrosion by preventing water leaks. The study presents a method to create continuity by casting a continuity diaphragm over supports and then post-tensioning the top end of the girders. The method exhibits all the advantages of a continuously post-tensioned technique. In the study, a bridge with three continuous spans was tested by using different truck loads at different positions. Stress on the girders and diaphragm were monitored by using the attached and impeded strain gages and a rosette. A three-dimensional finite element model was developed by using ANSYS and validated for the tested bridge. The FE model was used to analyze the transfer of stress between adjacent girders and spans. The results of FE model analysis indicated a strong correlation with the live load test data. Additionally, the results of the parametric study indicated that post-tensioning for continuity decreases the positive moments in the girders and leads to an increase in the transfer of stress between adjacent spans. It is expected that the results of the study will provide baseline data for these types of bridges.