Shear Resistance Mechanism of Posttensioned Precast Concrete Members

Abstract

An analytical model to investigate the shear resistance mechanism of a posttensioned precast concrete (PPC) member is proposed. The model is based on the truss mechanism. The compatibility of strains and the equilibrium of stresses of the shear cracked concrete, prestressing steel, and shear reinforcement are applied to the shear model. The proposed truss model consists of three stress zones (zones 1, 2, and 3). Triangle struts of cover concrete subjected to uniaxial compressive stress are defined as zone 1. Biaxial stress zones of diagonally cracked concrete between the longitudinal bar and prestressing steel are defined as zone 2. Zone 3 is defined as the diagonally cracked concrete zone between both compression and tension prestressing steels. The model considers the bond characteristics of prestressing steel. The proposed truss model is useful to predict not only shear strength, but also the shear deformation, tensile stress in shear reinforcement, and failure mode of a PPC member. By comparison of experimental and analytical results, an accuracy of analytical results by the proposed method was verified. The proposed method evaluated experimental results, which are shear strength, shear strain, and tensile stress in shear reinforcement in a good accuracy.