Influence of Cracking on Effects of Restrained Deformations in a Post-tensioned Concrete Bridge

Imposed and restrained deformations cause stresses in continuous concrete bridges, and in analyses of the superstructure these stresses are usually reduced to some degree due to creep and cracking of concrete. This study examines cracking and redistribution of stresses in a bridge superstructure under the loads and load combinations used in the original bridge design. The subject of this study is a three-span post-tensioned continuous concrete cantilever beam bridge. The bridge was analysed with non-linear calculation utilising the general force method and moment-curvature relationships. The analysis yielded the bending stiffness of the post-tensioned bridge superstructure as a function of bridge length under different loads. It was discovered that the secondary moment from prestressing force increased as the bending stiffness of the central span decreased due to cracking under external loads, which is not normally considered in design. The bending moment effects of linear temperature difference and support settlement decreased as expected as the superstructure bending stiffness decreased. The analysis provided new information on the effects of secondary moment from the prestressing force and on the difference between the cracked state and the linear elastic analysis of the concrete bridge superstructure.