Evaluation of Shrinkage-Induced Deflections of Composite Slabs with a Simplified Design Approach and a Hygro-Thermo-Chemical-Mechanical Model

Composite steel-concrete construction is widely used throughout the world for building and bridge applications. This paper focuses on the service behaviour of composite and post-tensioned composite floor slabs and how these are influenced by shrinkage effects. Research carried out in recent years has highlighted the occurrence of a non-uniform shrinkage profile that occurs through the thickness of a composite slab due to the inability of the concrete to dry from its underside because of the presence of the profiled steel sheeting. Two approaches are considered in this paper for the evaluation of the non-uniform shrinkage profile, one based on a simplified approach and one relying on a hygro-thermo-chemical-mechanical model. The deflection predictions produced by the non-uniform shrinkage profiles (obtained with the two approaches) are then calculated with a design procedure available in the literature. In the first part of the paper, the main factors influencing the composite shrinkage response are introduced, followed by the main features of the design model used for the deflection predictions and of the two approaches presented for the evaluation of the non-uniform shrinkage profiles. The adequacy of the two approaches is then evaluated by comparing the calculated long-term deflections with those measured experimentally from long-term tests carried out on selected post-tensioned composite slab samples that have been reported in the literature.