Strengthening of Continuous Composite Bridges

Abstract

The purpose of this first phase of a continuing research program is to examine the potential for strengthening continuous composite bridges by post‐tensioning. Testing of a one‐third scale bridge model and finite element analysis are used to determine the effects of various straight‐tendon posttensioning schemes. Because of both longitudinal and transverse distribution, the effects of posttensioning are complex. When asymmetrical posttensioning arrangements are applied to the bridge, the resulting stresses add to the dead load stresses in some regions of the model bridge. Symmetrical posttensioning of negative moment regions results in smaller stress reductions than symmetrical posttensioning of positive moment regions. Symmetrical posttensioning of positive moment regions has significant beneficial effects in both negative and positive moment regions. Vertical loads applied to the posttensioned model bridge either increase or decrease tendon forces, depending on the positions of the loads and tendons. Testing and analysis indicate that symmetrical posttensioning could improve service load stresses in continuous composite bridges.