Long-Term Behavior of Composite Beams under Positive and Negative Bending. II: Analytical Study

Abstract

The creep, shrinkage, and cracking of concrete may induce time-dependent changes in the stresses, internal forces, and deflections of steel-concrete composite beams. This paper presents an analytical model to consider these effects in analyzing the long-term behavior of composite beams under service loads using the step-by-step procedure. Under negative moments, the model accounts for the cracking, stress relaxing, tension stiffening, creep, and shrinkage of concrete. Meanwhile, a method is proposed to calculate the maximum crack width of the concrete slab by considering the shrinkage and creep effects. Four composite beams continuously loaded for about 3 years were analyzed using the proposed model. A good agreement is observed between the experimental results and the calculations by the proposed model. A discussion is also made about the aging coefficients in the age-adjusted effective modulus method under different loading conditions.