Field Investigation of a Continuous Composite Prestressed I-Beam Highway Bridge Located in Jefferson County, Illinois

摘要

Measurements of camber and strain in a prestressed concrete highway bridge were made over a period of 3.3 years. The bridge was made using precast, pretensioned I-beams which were made continuous for live-loads by reinforcement in the cast-in-place deck. The initial camber of about one in. in 72-ft span girders increased by about 75 percent within the first few weeks after release, and then changed only slowly. Only minor movements have occurred since the deck was cast. The same general trends have been observed in the strain measurements, with only small changes occurring after about two years. The shortening of the girders has amounted to slightly over one-in., in addition to temperature effects. Strain measurements on the bridge and on creep and shrinkage specimens indicate that the concrete undergoes expansion and contraction on an annual cycle, apparently in response to the increased average relative humidity during the winter months and the lower humidity during the summer. (Author)