Title:
Tendon Stress at Ultimate in Continuous Unbonded Post-Tensioned Members: Proposed Modification of ACI 318, Eq. (18-4) and (18-5)
Author(s):
Mohamed H. Harajli
Publication:
Structural Journal
Volume:
109
Issue:
2
Appears on pages(s):
183-192
Keywords:
external prestressing; flexure; post-tensioning; prestressing; slabs; stress; unbonded tendons
DOI:
10.14359/51683629
Date:
3/1/2012
Abstract:
Using plastic analysis and the concept of the collapse mechanism in continuous members, a general strain compatibility equation and a direct design expression for calculating the stress fps in unbonded tendons at ultimate were developed. The developed approaches take into account the important parameters that influence fps in an elegant and accurate manner. This paper presents a thorough discussion of the application of the design expression, verifies its accuracy in comparison with test data and other available expressions, and proposes that it forms the foundation for modifying Eq. (18-4) and (18-5) of ACI 318-08 for computing fps. A design example of a continuous unbonded post-tensioned slab is provided to illustrate the use of the compatibility approach and the direct design expression.