An approximate nonlinear design procedure for partially prestressed concrete beams

Abstract The theoretical basis and the main results of an approximate nonlinear design procedure which attempts to predict the behavior at ultimate of prestressed and partially prestressed concrete members is presented. Difficulties encountered in simulating the actual behavior of concrete and steel are discussed; particular emphasis is put on comparing the various available stress-strain relationships for prestressing steels, and observed variability in their actual properties. Recommended equations and corresponding coefficients are given. Typical results showing the influence on ultimate behavior of major variables such as the type and amount of prestressing steel, the amount of nonprestressed tensile and compressive reinforcement, and the ultimate concrete compressive strain are presented and compared with code derived results. They help point out where the code recommendations, if used, may lead to an unsafe design and what modifications may be needed to make them more representative of observed trends.