Title:
Development Length Criteria: Bars Not Confined by Transverse Reinforcement
Author(s):
David Darwin, Steven L. McCabe, Emmanuel K. Idun, and Steven P. Schoenekase
Publication:
Structural Journal
Volume:
89
Issue:
6
Appears on pages(s):
709-720
Keywords:
bond (concrete to reinforcement); bridge specifications; building codes; deformed reinforcement; development; lap connections; reinforcing steels; splicing; structural engineering; Structural Research
DOI:
10.14359/4158
Date:
11/1/1992
Abstract:
An expression that accurately represents development and splice strength as a function of concrete cover and bar spacing is developed. The expression is then used to establish and evaluate modifications to the bond and development provisions of the ACI Building Code (ACI 318-89) for bars in concrete members that are not confined by transverse reinforcement. The expression for development and splice strength is similar in form to expressions developed by other researchers but is obtained using techniques that limit the effects of unintentional bias in the test data. The resulting expression provides a more accurate representation of development and splice strength than do the earlier expressions, and it provides better guidance when there is a significant difference between the concrete cover and one-half of the clear spacing between bars. Proposals for new design criteria, including one under study by ACI Committee 318, are compared. Each of the new proposals contains design criteria that are superior to the current development length provisions (ACI 318-89); however, the criteria differ in terms of relative safety, economy, and ease of application. Side-by-side comparisons in design offices are recommended. In all cases, an additional development length modification factor of 1.1 is recommended for reinforcing steels with specified yield strengths in excess of 60,000 psi (414 MPa).