Rational modeling for cracking behavior of RC slabs in composite beams subjected to a hogging moment

Cracking of the reinforced concrete (RC) slab is a critical problem for a composite beam subjected to a hogging moment, which hinders its application to indeterminate composite structural systems. An efficient numerical method based on the fiber beam-column model is developed for predicting the full-process nonlinear crack width development of composite beams. Several significant modeling issues involving the modeling strategies, selection of material constitutive laws, consideration of shrinkage effect, and determination of average crack spacing are discussed in detail. Rational modeling parameters are recommended and validated by several previous experiments: (i) the slight mesh-dependency can be neglected, and the midpoint integration rule with 6 and 4 uniformly distributed fibers for the slab concrete and the steel beam web, respectively, can give results with sufficient accuracy; (ii) the crack width-load curve obtained through FE analysis should be modified to rationally consider the shrinkage effect of the slab concrete with the initial shrinkage strain of about 300 mu epsilon: (iii) it is rational to select the value of the average crack spacing as the transverse reinforcement spacing of the RC slab; and (iv) the constitutive laws of the tensile slab concrete and reinforcement have minor influence on the global crack width-load response, especially in the stage after the stabilization of the cracking distances. The selected smeared material constitutive laws are recommended to give a smooth and rational curve for the stage before stabilized cracking. (C) 2018 Elsevier Ltd. All rights reserved.