A step-by-step method for time-dependent analysis of composite beams

Composite beams composed of reinforced concrete slab and steel section joined by mechanical connectors. The concrete slab provides compressive strength, fire resistance, and floor surface, whereas the steel section provides high tensile strength. Steel-concrete composite structures are widely used in frame buildings and bridges due to their economic and structural advantages. In the existing literature, a hybrid analytical-numerical procedure is available for service load analysis of steel-concrete composite beams considering cracking, creep, and shrinkage in concrete. The procedure uses an age-adjusted effective modulus method (AEMM) to model creep and shrinkage effects. The AEMM is computationally efficient however, it compromises accuracy owing to the use of the same aging coefficient for creep and shrinkage. Therefore, in this paper, a step-by-step method (SSM) has been proposed for modeling the creep and shrinkage effects. The method takes into account the progressive concrete cracking with time due to creep and shrinkage. The method is computationally efficient for large composite frame buildings compared to the finite element method since no discretization of the member, along the length and/or across the cross-section, is needed. The method has been validated against experimental results available in the literature. It is observed that the SSM has greater accuracy than the AEMM.