Performance of RC slabs under the combined effect of applied loads and restrained shrinkage

One of the key factors towards a proper service life behaviour of reinforced concrete (RC) structures is the adequate control of crack widths by the reinforcement, as to ensure adequate durability. However, currently existing methodologies for reinforcement design are not satisfactory in providing instructions for adequate control of crack widths when RC members are subjected to high restraints to deformation (e.g. due to shrinkage), in combination with vertical loads (both dead and live). This is a typical situation in RC slabs applied in buildings. The reason of the unsatisfactory character of current design provisions and recommendations is related to the very high complexity of phenomena at interplay, particularly the non uniform distribution of moisture in concrete that inherently brings non-uniform distribution of stresses (in space and time) due to drying shrinkage, which in turn have important influence in the process of crack development. This paper intends to contribute for deepening knowledge on these processes by deploying a thermo-hygro-mechanical simulation framework, which is described and validated, to the analysis of a highly restrained slab in service load conditions.