TIME-DEPENDENT BEHAVIOR OF CONTINUOUS COMPOSITE BEAMS AT SERVICE LOADS

An analytical model of the behavior of continuous composite beams under sustained service loads is described. Each beam consists of a rolled or fabricated steel I-section acting compositely with a reinforced concrete slab attached to the top flange. The analysis accounts for cracking of the concrete slab in the negative moment regions at each interior support, as well as the time-dependent deformation caused by creep and shrinkage in the concrete slab. Measurements from a series of full-scale continuous composite beams, which were tested by the writers in a separate study for a period of 340 days under sustained uniformly distributed loads, are used to validate the theoretical model. Close agreement is observed between analytical and experimental results. Finally, the analytical model is used to investigate the effects of material nonlinearity on structural behavior.