Stress-strain model for laterally confined concrete

High strength concrete (HSC) with highly desirable structural properties can lead to significant cost savings in heavily loaded lower story columns of concrete structures. Its use has however, been limited by a concern regarding an increased brittleness compared to normal strength concrete. It is well established that the ductility of HSC columns can be increased by confinement of the core of concrete columns by lateral steel reinforcement. Confining pressure applied by the reinforcement is a function of the lateral strain of concrete. Therefore establishing axial stress, axial strain, and lateral strain relationships is a timely concern. Based on shear failure of concrete, a simple strain-based model is proposed in this paper. It is developed using prevailing test results for HSC with active confinement.