A Simplified Shear Design Method For Post Tensioned Concrete

Abstract

Shear forces are one of the primary forces that need to be accounted for when designing a prestressed, post tensioned, or regular reinforced concrete member. Shear forces can cause brittle, and often disastrous failure if a section is not properly designed. The ACI 318-19 code has several methods for calculating the nominal capacity of various concrete members. This research project considers the current code equations for prestressed concrete, and a new modified version of the equation for non-prestressed members that allows unification of concrete shear design as an alternate simplified method. The goal of this project is to evaluate a more straight-forward shear design approach for post-tensioned members. The detailed method used in pretensioned members models the effects of inclined and web shear types of failures reasonably well for determinate members. However, the typical post-tensioned member is often indeterminate with a series of parabolic tendon profiles and is more complicated to model with potentially little gain in reducing stirrup requirements. A basic approach that is similar to the new non-prestressed equations in ACI 318-19 is provided as an alternate method. While the proposed method would be a conservative option for pretensioned members, the likely application is in continuous post-tensioned members.