International Concrete Abstracts Portal

Title: Proposed Development Length Equation for Plain Bars

Author(s): Lisa R. Feldman, Umesh Poudyal, and John Cairns

Publication: Structural Journal

Volume: 115

Issue: 6

Appears on pages(s): 1615-1623

Keywords: bar shape; bar size; casting position; development length; historical structures; lap splice; plain reinforcement; structural evaluation; structural safety

Date: 11/1/2018

Abstract:
ACI 562-16 permits development and splice lengths of plain reinforcing bars to be assessed using code provisions that were in effect at the time of construction. However, previous research has shown that margins of safety provided by these provisions varied markedly between successive code editions and were unsafe for certain scenarios. A reliability-based equation, calibrated for safety in accordance with U.S. practice, is therefore developed from a test database of 29 viable splice specimens and 268 beam-end specimens. The subsequent comparison of results provided for plain bars using the proposed equation and those included in ACI 318-14 for deformed bars suggest that the historical rule-of-thumb that bottom-cast plain round bars require twice the development length of deformed bars is likely slightly conservative, while the considerable top-cast effect for plain bars results in their development length being almost three times that required for deformed bars.