Effects of Increasing Allowable Compressive Stress at Prestress Transfer

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Title: Effects of Increasing Allowable Compressive Stress at Prestress Transfer

Author(s): David B. Birrcher, Oguzhan Bayrak, and Michael E. Kreger

Publication: Structural Journal

Volume: 107

Issue: 1

Appears on pages(s): 21-31

Keywords: compressive stress; flexural cracking; prestress transfer.

Date: 1/1/2010

Abstract:
The benefits and weaknesses of increasing the allowable compressive stress at prestress transfer are presented in this paper. A historical background of the allowable release stress in compression, including a summary of several research studies that investigated this stress limit, is provided. A simple design example is used to quantify potential production and design benefits of increasing the allowable stress. The applicability of these benefits is also discussed. Finally, test results of 36 pretensioned beams that were subjected to maximum compressive stresses at release ranging from 0.46fci' to 0.91fci' are reported and analyzed. The experimental results suggest that increasing the allowable release stress in compression at midspan of a member to 0.65fci' or 0.70fci' is possible. Premature flexural cracking was observed for members subjected to midspan release stresses in excess of 0.70fci'.