CONSTITUTIVE LAWS OF SOFTENED CONCRETE IN BIAXIAL TENSION-COMPRESSION

A softened truss model was developed during the past decade at the Uni versity of Houston for predicting the behavior of reinforced concrete subjected to shear and torsion. The model, based on the conditions of equilibrium and compatibility: utilizes realistic constitutive laws fo r concrete and reinforcement. The required constitutive laws for concr ete and reinforcement were studied led by testing 22 full-size reinfor ced concrete panels. These large test panels were subjected to tension in one direction and compression in the perpendicular direction, usin g the universal panel tester at the University of Houston. Test result s relealed that the strength and stiffness of concrete in compression were softened primarily by the presence of tensile strains in the perp endicular direction. The effect of other parameters, e.g., load path p ercentage of steel, and spacing of reinforcing bars, was evaluated. Ba sed on these tests, improved softened stress-strain relationships of c oncrete in compression were developed.