Long-term Stress of Simply Supported Steel-concrete Composite Beams

The theoretical model to compute the long-term stress of simply supported steel-concrete composite beam was deduced. The model includes the effects of steel bars in concrete slab, concrete shrinkage and creep. The computed results agreed well with the test results. On this basis, the effects of factors such as concrete age to loading, longitudinal reinforcement ratio in concrete slab, concrete slab width, steel beam height, environmental yearly average relative humidity, external load value and concrete strength on the long-term stress of steel-concrete composite beams are discussed. The results show that the additional stress at the top of concrete slab is tensile stress and that at the bottom of steel beam is compressive stress. The ratio of steel beam to concrete slab thickness, as well as concrete slab width and the longitudinal reinforcement ratio in concrete slab can not be ignored. Concrete strength, external load value and concrete age to loading have relatively bigger effect as well, But the environmental yearly average relative humidity has less impact. The fruits are useful to the design and application of steel-concrete composite beams.