Title:
Stress at Ultimate in Unbonded Post-Tensioning Tendons: Part 1--Evaluation of the State of the Art
Author(s):
Antoine E. Naaman and Fadi M Alkhairi
Publication:
Structural Journal
Volume:
88
Issue:
5
Appears on pages(s):
641-651
Keywords:
bond (concrete to reinforcement); post-tensioning; prestressed concrete; prestressing steels; standards; strength; stresses; unbonded prestressing; Structural Research
DOI:
10.14359/2763
Date:
9/1/1991
Abstract:
This study deals with the stress at ultimate ps in unbonded tendons of prestressed and partially prestressed beams for the purpose of computing their nominal bending moment resistance. The first part comprises mainly: 1) some background information followed by a comprehensive review of existing experimental and analytical investigations dealing with the stress at ultimate in unbonded tendons; 2) a summary of prediction equations for fps suggested by different investigators and in various North American and European codes; and 3) an evaluation of typical prediction equations achieved by comparing predicted with experimentally observed results. The experimental results were obtained from nine different investigations totaling 143 beam tests described in the technical literature and carried out since 1960 in various parts of the world. In the second part of this study, the background for a new rational methodology for analysis of beams prestressed with unbonded tendons is covered and a new prediction equation for fps at ultimate is developed. The equation is shown to account for most of the variables found important in the analysis of beams prestressed with unbonded tendons and to predict experimental results with much better accuracy than any of the existing prediction equations reviewed in the first part. The proposed equation modified by an appropriate safety factor is recommended for adoption by the ACI Building Code.