A hygro-thermo-chemical-mechanical model for the service response of composite steel-concrete floor systems

Composite steel-concrete floor systems are widely used throughout the world for building applications. This paper focuses on the service behavior of composite floors that usually consist of composite slabs in steel framed construction and of post-tensioned composite slabs in concrete structures. In the initial part of the paper, recent experimental work carried out on composite floor slabs is outlined and it includes the description of the occurrence of a non-uniform shrinkage profile through the slab thickness due to the inability of the concrete to dry from its underside because of the presence of the profiled steel sheeting. A hygro-thermo-chemical-mechanical model is then presented to predict the service response of composite floors. The proposed approach is validated against experimental data collected on post-tensioned composite samples. For this purpose, an inverse analysis procedure is applied for the characterisation of the numerous material parameters and the multi-physics model is used to predict the non-uniform shrinkage gradient. Based on this, a design model available in the literature is then used to evaluate the long-term deflections and compared the calculated values against long-term experimental measurements. Simplified models have also been used to determine the shrinkage profile for benchmarking purposes. It has been shown that the numerical and experimental deflection comparisons show good agreement when determined using a non-uniform shrinkage distribution, while the calculated values underestimate the observed deflections when obtained with a uniform shrinkage profile.