Validation of Thermo-hygro-Mechanical FEM Analysis of Thick Restrained RC Members by Comparison with Experiments

Abstract

Crack width control is an important design task to achieve the required durability and serviceability of reinforced concrete (RC) structures. The thickness of the member is an important contributing factor for the mode of cracking—and thus for the required reinforcement for crack control. While in thin RC elements, e.g. industrial floors or tank walls, visible cracks usually penetrate through the entire element thickness, in thick elements with common reinforcement configuration (reinforcement is located near the surface) the cracking process is much more complex: initially, a primary crack occurs and separates the element over its entire thickness; and in addition, secondary cracks may occur due to the transfer of the steel force in the primary crack back into the concrete by bond action. These secondary cracks do not penetrate through the entire thickness, but end somewhat behind the surface zone. This paper presents the validation of a thermo-hygro-mechanical framework for simulation of the cracking process in thick restrained RC members. The study focusses on the short-term experimental campaign on restrained reinforced concrete panels made at TU Graz. The experimental measurements are compared with the results of the finite element simulation. The comparison is made for the crack patterns, the crack width development for primary and secondary cracks and the development of the restraint force in function of the imposed elongation. In addition, a parametric study is performed to investigate the drying shrinkage effect on the long-term crack width evolution of primary and secondary cracks.