Flexural behaviour of concrete-steel hybrid bridge girders

Abstract

The experimental results from a full-scale test are compared with analytical predictions in order to investigate the behaviour of a hybrid bridge girder with a reinforced concrete web and steel flanges. A linear analysis indicates that restrained shrinkage had a significant influence on initial cracking of the concrete web. The longitudinal strains, predicted by a nonlinear flexural analysis accounting for shrinkage and construction stages, compare well with the strains measured during the test. The average widths of the flexural cracks at the service load level are predicted using an empirical average crack spacing approach. The modified compression field theory is used to predict the diagonal cracking of the web due to combined shear and bending moment. A rigorous nonlinear analysis indicates that the effects of creep, load-cycles, and shear deformation must be accounted for in predicting the displacement of the girder. Finally, sectional strength calculations indicate that the distributed longitudinal reinforcement in the web contributes significantly to the flexural capacity of the hybrid girder. Key words: bridges, composite, cracking, girder, hybrid, reinforced concrete, structural design, tests.