Long-term deformations in continuous composite concrete slabs

Relatively little research has been reported on the time-dependent in-service behaviour of continuous composite concrete slabs with profiled steel decking as permanent formwork and little guidance is available for calculating long-term deflections. The drying shrinkage profile through the thickness of a composite slab is greatly affected by the impermeable steel deck at the slab soffit, and this has only recently been quantified. This paper presents the results of longterm laboratory tests on continuous composite slabs subjected to both drying shrinkage and different levels of sustained load. The paper provides experimental evidence of the dominant role played by drying shrinkage in the long-term deflection and redistribution of internal actions in continuous composite concrete slabs. An analytical procedure for the determination of the time-dependent deflections in continuous composite slabs is described and the results of analyses are presented and compared with the experimental data.