Title: Relaxation Testing Of Stressing Strand Test Method And Suggested Improvements To AS 1311

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Publication: CIA

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Date: 2/13/2011

Abstract:
Stressing strand is a critical structural component in bridge and other pre or post tensioned structures. The quality and conformance of stressing strand to design codes including AS1311 is fundamental. The paper examines the requirements of a relaxation test. Materials standards for strand specify relaxation at 1000 hours (6 weeks) as a practical means of ensuring strand quality. A bridge has to perform over a design life of 100 years, and to ensure this, an estimate of strand relaxation at 10,000 days (30 years) is required in the Australian Bridge Design Code. The need to extrapolate a 1000 hour test to 10,000 days (240,000 hours) places significant demands on the accuracy of the readings in the 1000-hour test. The paper makes recommendations about improvements to AS 1311 to standardize testing and additional requirements to be included in the standard.