Predicting shrinkage induced curvature in plain and reinforced concrete

Shrinkage induced curvatures in reinforced concrete elements are thought to be affected only by section geometry and distribution/ratio of reinforcement. The variation in the level of internal restraint caused by the non-uniform distribution of concrete constituents within the section, however, can also lead to additional shrinkage induced deformations, and potentially to larger than expected deformations in critical structural elements, even under service conditions. This study examines experimentally the development of non-uniform shrinkage strains in unreinforced as well as symmetrically and asymmetrically reinforced concrete elements. Results confirm that shrinkage is non-uniform due to the variations in internal restrains (coarse aggregates and reinforcement). The addition of steel fibres mitigates this effect and reduces overall shrinkage curvature. A prediction model for shrinkage induced curvature of plain and reinforced concrete is proposed, taking into account the non-uniform distribution of concrete constituents. The proposed model yields results in good agreement with experimentally observed values of shrinkage curvature and can be used to improve the predictions of design guidelines.