A simplified method for predicting early-age stresses in slabs of steel-concrete composite beams in partial interaction

Thermal effects due to the heat produced by cement reaction and shrinkage deformations affecting concrete generally results in stresses that can lead to early age cracking in the concrete slab of composite beams. This work provides a simplified approach for determining the time evolution of stresses developing at early age in curing concrete slabs of composite beams. Specifically, the method generally used in practice and based on a simple sectional analysis is extended to the case of steel-concrete composite beams in partial interaction. The time evolution of the force-slip relationship characterising the shear connector response as a result of the concrete curing process is also taken into account by means of a simple assumption corroborated by some experimental results available in the literature. The results obtained by applying the two proposed methods are compared to those achieved by means of the general practice-oriented procedure. Different types of cement, featuring a variable time evolution of the hydration process, are taken into account. Moreover, the effect of different external temperature at casting is also considered. It is worth highlighting that the proposed method enhances the predicting capability of the current practical ones, with almost no increase in calculation effort.