Analysis of the Flexural Strength of Prestressed Concrete Flanged Sections

Abstract

In this article, provisions of the AASHTO Standard and LRFD Specifications are compared to results from strain compatibility analyses of reinforced and prestressed concrete non-rectangular sections using realistic stress-strain models for the constituent materials. The goal of this study was to identify design procedures that more accurately represent the actual behavior of such members. The authors propose modifications to the LRFD procedure to increase the accuracy of computed moment capacities for typical sections. Computed flexural capacities are compared to measured flexural capacities obtained from existing tests to validate the proposed modifications. The authors conclude that inconsistencies exist between the AASHTO LRFD and AASHTO Standard Specifications in predicting the response of reinforced and prestressed concrete sections that are non-rectangular. The differences are related to the selection of the neutral axis depth at which transition from rectangular section behavior to T-section behavior occurs, and the amount of the top flange overhang contribution to the internal compressive force. The authors recommend that the procedure currently used by the AASHTO LRFD Specifications should be modified in order to more accurately predict the response of flanged prestressed concrete sections at ultimate capacity.