Time-Dependent Deformations and Losses in Concrete Bridges Built by the Cantilever Method

A method is presented for the analysis of time-dependent deformations of post-tensioned concrete bridge superstructures which are erected by cantilever methods. The method takes into account any arbitrary creep and shrinkage properties of the concrete, friction between strand and ducts, relaxation of the steel stress, and construction loads. A step-by-step procedure is presented which takes into account the creep of concrete under variable stress, variations in Young's modulus of concrete, and all elastic changes in stress accompanying the construction of additional segments. The analysis method was used to study the effects of variations of the parameters on the long-term behavior of two bridges which were built and designed following quite different criteria. Excellent agreement between measured and computed curvatures and strains were found in the two cases for which experimental data were available.State of Illinois Department of Transportatio