3D Thermo-Hygro-Mechanical Simulation of a RC Slab Under Restrained Shrinkage and Applied Loads: Influence of the Reinforcement Ratio on Service Life Behaviour

The structural design of reinforced concrete (RC) structures requires the use of adequate methodologies for control of crack widths, in order to ensure proper service life behavior. When RC elements are subjected to the combined effect of restrained deformations and external loads, which is a relatively common situation in civil engineering structures, current design codes and recommendations generally fail to provide specific/clear instructions for measures to be taken for reinforcement design in view of crack width control. This paper intends to show the influence of different approaches for quantification of the necessary reinforcement on the service life behavior of these structures, through conduction of a parametric study. Such study is performed in order to understand how the variation of the longitudinal reinforcement affects the structural behavior of a solid one-way RC slab subjected to restrained shrinkage and external applied vertical loads (in quasi-permanent load combination). The structural behavior of the slab is simulated for 5 distinct quantities of longitudinal reinforcement, with a 3D thermo-higro-mechanical model, where the non-uniform distribution of stresses due to heat of hydration and drying shrinkage are considered. The attained results allowed conclusions to be withdrawn in regard to the expected behavior when reinforcement is underdesigned (by neglecting restraint) or overdesigned (by considering the cracking force of concrete when evaluating axial restraint). Intermediate solutions, matching some simplified approaches in the literature where found to be the most reasonable.