Post-fire deterioration and prestress loss in steel tendons used in post-tensioned slabs

K. J.N. MacLean, L. A. Bisby, C. C. MacDougall

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Unbonded post-tensioned (PT) concrete slabs have been widely used in Canada and the United States since the 1960s, as they allow increased span-to-depth ratios and excellent control of deflections compared to non-prestressed reinforced concrete flexural members. The satisfactory fire performance of unbonded, PT concrete slabs in North America was established by a series of standard fire tests performed in the United States during the 1960s. However, there is a paucity of data on the effect of elevated temperatures on cold-drawn prestressing steel, both in terms of post-fire residual mechanical properties and high-temperature stress relaxation, which can lead to significant prestress loss both during and after a fire. To aid in the post-fire evaluation of PT concrete floors, a series of high-temperature residual tension tests on prestressing steel is presented, along with a second series of tests that illustrate the irrecoverable and significant loss of prestress force that may result from steel relaxation (creep) during a fire. A preliminary model is presented that can be used to predict the change in prestress force and allow for the computation of flexural capacity of a PT slab after a fire.

Original languageEnglish
Title of host publicationAmerican Concrete Institute - Designing Concrete Structures for Fire Safety Session at the ACI Spring Convention 2007
Pages143-169
Number of pages27
Edition255 SP
Publication statusPublished - 1 Dec 2008
EventDesigning Concrete Structures for Fire Safety - ACI Spring Convention 2007 - Atlanta, GA, United States
Duration: 22 Apr 200726 Apr 2007

Publication series

NameAmerican Concrete Institute, ACI Special Publication
Number255 SP
ISSN (Print)0193-2527

Conference

ConferenceDesigning Concrete Structures for Fire Safety - ACI Spring Convention 2007
CountryUnited States
CityAtlanta, GA
Period22/04/0726/04/07

Keywords

  • Assessment
  • Fire
  • High-temperature creep
  • Post-tensioned slabs
  • Prestressing steel
  • Relaxation
  • Repair

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