Shrinkage-free tension stiffening law for various concrete grades

The present study proposes a new tension stiffening law for reinforced concrete (RC) that takes into account the shrinkage effect occurring prior to the external loading. Due to the restraining action of reinforcement, shrinkage induces tension stresses in the concrete which may significantly reduce the crack resistance and increase deformations of the RC member. The proposed tension stiffening model is based on the test data of seven experimental programs reported in the literature, including 108 RC tension members covering a wide range of concrete grade, reinforcement ratio and bar diameter. The study has shown that shrinkage drastically changes the shape of tension stiffening relations with reinforcement ratio being the most important parameter responsible for this effect. This study reports a limited validation analysis of the proposed constitutive law based on experimental data reported herein. For that tests on four tensile RC members with measured free shrinkage strain have been carried out. The comparative analysis has shown good agreement between the experimental and predicted load-strain and tension stiffening relations.