Title: Tests of Unbonded Seven-Wire Tendon with Broken Outer Wires

Author(s): Colin MacDougall and F. Michael Bartlett

Publication: Structural Journal

Volume: 100

Issue: 5

Appears on pages(s): 581-588

Keywords: concrete; friction; post-tensioning; prestress; test; unbonded tendon

DOI: 10.14359/12799

Date: 9/1/2003

Abstract:
This paper documents six tests of unbonded seven-wire monostrand tendons with one or two broken outer wires. The objective of the study was to investigate experimentally the behavior of uncorroded monostrand tendons with broken wires and to assess the range of application of assessment procedures used in practice, such as the screwdriver penetration test. Specimens with 9, 13, and 15 mm diameters were tested using an 18.3 m strongback beam that simulates the load and boundary constraints typical of an unbonded, post-tensioned concrete slab. Remaining prestress fraction measurements and strain distributions along the length of the broken and unbroken wires were obtained for each test. It was observed that: strains in broken wires increased with distance from the break; strains in unbroken wires of tendons with two diametrically opposed broken wires were equal at each cross section and decreased with distance from the break; strains in unbroken wires of tendons with a single break were not equal at each cross section, with maximum strains in the two wires adjacent the broken wire; and the remaining prestress force is significantly increased by inter-wire friction.