TIME-DEPENDENT DEFORMATION IN SEGMENTAL PRESTRESSED CONCRETE BRIDGES

A rational analytical procedure for estimating the time-dependent behavior of segmental prestressed concrete bridges built by the cantilever method is presented. It is based on a step-by-step numerical procedure which attempts to account for most of the important parameters that influence the time-dependent behavior of such structures, and the procedure was incorporated in a computer program. Comparisons were made between computed strains and those measured in the Kishwaukee River Bridge at Rockford, Illinois. Good agreement between the two sets of values was obtained as long as the computations were based on the creep properties of samples of concrete from the bridge, for the particular case where the creep specimens were stored outdoors in the same environment that the structure experienced. In this particular structure shrinkage strains in the concrete dominated the time-dependent response. Creep deformations were relatively small because most of the precast segments were old when they were erected, and relaxation of steel stress was small because of the type of post-tensioned bar reinforcement used in the structure. (FHWA)