Elongation Tolerance for Short Tendons in Post-Tensioned Building Structures

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Title: Elongation Tolerance for Short Tendons in Post-Tensioned Building Structures

Author(s): Carol Hayek and Thomas H.-K. Kang

Publication: Structural Journal

Volume: 114

Issue: 04

Appears on pages(s): 795-802

Keywords: bonded; elongation; measurement; post-tensioned building structures; short tendons; tolerance; unbonded

Date: 7/1/2017

Abstract:
Elongations have been used to assess the forces inside post tensioned tendons immediately after the post-tensioning operation. However, the measured elongations are characterized by a high degree of uncertainty and variability due to site tolerances, and that the calculated elongations are based on the ideal equations using theoretical parameters. Building codes acknowledge such variability as a limitation and include tolerances for the elongation deviations between the calculated and measured values. Even so, the specified tolerances are quite stringent and unrealistic for relatively short tendons. In this study, to resolve this issue, a statistical analysis is carried out using a large database of tendon elongations measured from actual projects of bonded post tensioned building structures. Based on the analysis of the data collected, a practical and rational tolerance between measured and calculated elongations is proposed.