A hygro-thermo-chemical-mechanical model for the shrinkage prediction in composite steel-concrete floors

Composite steel-concrete slabs are widely used for building applications and they consist of reinforced concrete slabs cast on profiled steel sheeting. When used in building floors, their design is usually governed by serviceability limit conditions. Recent research has highlighted the occurrence of a non-uniform shrinkage profile that influences the slab deflection and that develops through the slab thickness due to the inability of the concrete to dry from its underside because of the presence of the steel sheeting. This paper presents a hygro-thermo-chemical-mechanical model formulated for the analysis of moisture transport and heat transfer suitable for the shrinkage deformation predictions of composite floor systems. In particular, the approach predicts the temperature and moisture variations that can take place over time in the concrete accounting for different exposure conditions. In the framework of a staggered approach, the outcomes of the initial hydro-thermo-chemical analysis are specified in input to the time-dependent mechanical model. The applicability of the proposed approach to composite floor slabs is validated against experimental measurements recorded over time for unreinforced companion concrete samples exposed with different surface conditions.