The Influence of Time Dependent Material Behavior on the Structural Performance of Prestressed Box Girder Bridge Superstructure

The time dependent material behavior is of particular importance in the study of the behavior of boxed girder prestressed concrete bridges. The stage by stage balanced cantilever method of construction of segmental bridge contributes further in their time dependent performance. In this work, in order to study the performance of cantilever prestressed concrete bridges in a time - span of 35 years, an attempt has been made to account for the factors and actions influencing the material time dependent behavior such as creep, shrinkage, the variation of elastic modulus and the loss of prestressing. For this purpose, a case study has been carried out on a three span continuous prestressed box-girder bridge. A three dimensional finite-element model has been constructed for the nonlinear stage by stage analysis taking into account the balanced cantilever construction method of segmental bridges, including the effects of loading history and material time-dependent behavior. The analysis results have been discussed in terms of the variation of stresses and displacements during the time span under consideration.
Finally, the effect of the time dependent material behavior on the performance of the bridge has been demonstrated and some suggestions have been made to improve the time dependent behavior of such bridge superstructures in the construction of new bridges as well as the retrofit of existing bridges.