Prediction of Stress in Bonded Strands at Flexural Strength

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Title: Prediction of Stress in Bonded Strands at Flexural Strength

Author(s): Jae-Hyun Park, Ho Park, and Jae-Yeol Cho

Publication: Structural Journal

Volume: 114

Issue: 03

Appears on pages(s): 697-705

Keywords: approximate equation; design codes; flexural strength; high strength; strands; stress

Date: 5/1/2017

Abstract:
With respect to prestressed concrete, important changes to the structural design codes and notable improvements of the materials have been made over the past decade. The most recent examples are the introduction of the net tensile strain to ACI 318 and the development of high-strength strands. The influences of the net tensile strain and high-strength strands have not been properly evaluated, however, or reflected in the related design code provisions; this is especially the case for the approximate equations that are used to calculate the stress in strands at the flexural strength. Therefore, in this paper, the approximate equations of the current ACI 318 and CSA A23.3 codes are investigated. A series of strain compatibility analyses revealed that the current approximate equations yield unconservative results for flanged sections and highstrength strands; based on these analyses, a modified version of an approximate equation is proposed to take into account the influences of flanged sections and high-strength strands.