Rational Determination of Friction Losses in Post-Tensioned Construction

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Title: Rational Determination of Friction Losses in Post-Tensioned Construction

Author(s): P.R. Gupta

Publication: Special Publication

Volume: 231

Issue:

Appears on pages(s): 129-144

Keywords: concrete; curvature; evaluation; force; friction;measurement; prestressing; slab; tendon; tension; unbonded;wobble

Date: 10/1/2005

Abstract:
Friction losses contribute about 50% of the total losses in post-tensionedconstruction. The original loss coefficients that were derived for earlier post-tensioningsystems are still being used in the ACI recommendations for unbonded construction.Some of these systems have not been used in the industry for almost 30 years.This paper presents a review of the current ACI recommendations of friction losses inunbonded construction. The paper also describes the theoretical development of asimple field technique to determine the curvature and wobble coefficients under fieldconditions. Results from initial testing are compared with the ACI recommendations andindustry practice.