Design method for long-term deflections of composite steel-concrete slabs considering non-uniform shrinkage effects

Existing long-term tests of composite steel-concrete slabs were summarised to investigate the influence of non-uniform shrinkage distributions on their long-term deflections, based on which the model to predict the non-uniform shrinkage profiles through the thickness of composite slabs was determined. A finite element model (FEM) was established based on MATLAB software, accounting for combined effects of non-uniform shrinkage, creep and concrete cracking, and a parametric study was then carried out to evaluate the effects of various parameters on the shrinkage deflections of composite slabs. Following the way to calculate the effective stiffness of composite slabs, design procedures to calculate the deflections induced by non-uniform shrinkage profiles were proposed for composite slabs. The results indicate that the deflections due to the shrinkage distributions account for 58%-86% of the total deflections of composite slabs. Concrete compressive strength and span-to-depth ratio are the key parameters that influence the shrinkage deflections of composite slabs. The results obtained by proposed design procedures are in good agreement with FE results, with the ratio of 0.971-0.997 and the correlation coefficient R² of 0.803-0.815.