Effects of the slab casting sequences and the drying shrinkage of concreteslabs on the short-term and long-term behavior of composite steel box girder bridges. Part 1

In this study, the time-dependent behavior of composite steel girder bridge s was investigated both theoretically and experimentally. The layer approac h was used as an analytical model to determine the equilibrium conditions i n a section, and to effectively consider the different material properties across the sectional depth. The effect of creep was studied in accordance w ith the first-order algorithm based on the expansion of a degenerate kernel of compliance function. In addition, the shrinkage effect of concrete was accounted for by the volume change of the concrete slabs. To verify the ana lytical results, field tests were performed on two actual bridges under con struction. Strain values on the top and bottom flanges were monitored 30 da ys after the deck concrete had been placed. Analytical results compared wel l with the experimental results. The ultimate shrinkage strain recommended in the specifications can be significantly different from the actual rate o f drying shrinkage, depending on field conditions such as concrete slump, t he ambient temperature, and the relative humidity. (C) 2000 Elsevier Scienc e Ltd. All rights reserved.