Title:
Tendon Stress and Flexural Strength of Externally Prestressed Beams
Author(s):
Chee-Khoon Ng
Publication:
Structural Journal
Volume:
100
Issue:
5
Appears on pages(s):
644-653
Keywords:
beam; bond; prestress; tendon.
DOI:
10.14359/12806
Date:
9/1/2003
Abstract:
Externally prestressed beams are structural concrete members where the prestressing tendons are placed outside of the concrete section. The flexural response of an externally prestressed beam has been commonly equated to that of a beam with internal unbonded tendons, for which most of the previous analytical studies give the stress in the tendon at ultimate flexure limit state as a function of the span-depth ratio of the beam. It is, however, shown in this study that the span-depth ratio has insignificant effect on the tendon stress at ultimate in externally prestressed beams. Tests carried out on prototype beams confirmed the analytical results. Therefore, a modified bond reduction coefficient is proposed for the evaluation of the flexural strength of externally prestressed beams based on strain compatibility and force equilibrium. Theoretical calculations based on this bond reduction coefficient and accounting for second-order effects were found to agree with the test results.