Title: Anchorage Strength of Closely Spaced Hooked Bars

Author(s): Ali Ajaam, Samir Yasso, David Darwin, Matthew O’Reilly, and Jayne Sperry

Publication: Structural Journal

Volume: 115

Issue: 4

Appears on pages(s): 1143-1152

Keywords: anchorage; beam-column joints; high-strength concrete; highstrength steel; hooks; reinforced concrete; reinforcement; spacing; staggered hooks

DOI: 10.14359/51702065

Date: 7/1/2018

Abstract:
The effect of close spacing on the anchorage strength of standard hooks is investigated. Sixty-seven simulated beam-column joint specimens were tested, each containing three, four, or six No. 5, 8, or 11 (No. 16, 25, or 36) hooked bars arranged in one or two layers with center-to-center spacing ranging from two to six bar diameters. Anchorage strengths are compared with those of specimens containing two hooked bars with spacings of six to 12 bar diameters. The results demonstrate that the provisions in ACI 318-14 tend to overestimate the anchorage strength of hooked bars as concrete compressive strength and bar size increase and as spacing between bars decreases. Decreasing center-to-center spacing below six bar diameters results in lower anchorage strengths than for hooked bars with wider spacing. The anchorage strength of hooked bars can be represented by considering the minimum of the horizontal and vertical spacing between bars.