SHRINKAGE BEHAVIOUR OF COMPOSITE STEEL-CONCRETE FLOORS USING A HYGRO-THERMO-CHEMICAL-MECHANICAL MODEL

Composite steel-concrete structures are widely used throughout the world for different applications. In the case of building systems, composite solutions can be specified and adopted in the form of composite slabs, composite beams and composite columns. Recent research carried out on the service behavior of composite floor systems has pointed out that a non-uniform shrinkage profile develops through the concrete thickness for a slab cast on profiled steel sheeting. These observations are particularly significant when considering that the design of composite floors is commonly governed by serviceability limit state associated with deflection limits. In this context, this paper provides a brief overview of the main factors influencing the service behavior of composite slabs and of a model capable of predicting their long-term deflections by evaluating the non-uniform shrinkage effects by means of hygro-thermochemical-mechanical model. This approach requires the use of an inverse analysis procedure to identify the large number of parameters of the multi-physics model. The results obtained with this refined strategy have been compared with those calculated with a simplified design approach that is available in the literature for the evaluation of the effects produced by non-uniform shrinkage. The adequacy of the proposed prediction model is then outlined by comparing the long-term deflections obtained with both multi-physics and simplified approaches with those measured experimentally from long-term tests carried out on selected post-tensioned composite slab samples that have been reported in the literature.