NEW RESEARCH REPORT: Development of Large High-Strength Headed Reinforcing Bars
The Charles Pankow Foundation (CPF) in partnership with the American Concrete Institute Foundation, the Concrete Reinforcing Steel Institute Foundation, and the Precast/Prestressed Concrete Institute, are pleased to announce the new research report, Development of Large High-Strength Headed Reinforcing Bars, is available for free download.
This research was conducted at the University of Kansas led by Principal Investigator David Darwin. This research expands the available data on the anchorage strength of high-strength headed reinforcing bars to include the largest sizes currently permitted in the ACI Building Code, No. 14 and No. 18, and use those results to verify the applicability of the currently proposed design criteria. Headed reinforcement is permitted under the provisions of ACI 318. Those provisions, however, limit the bar size to No. 11 and smaller. The study includes headed bars in concrete with nominal compressive strengths ranging from 5,000 to 16,000 psi to produce stresses in the bars at anchorage failure ranging from 55 to 148 ksi. Bar spacing ranges from 3 to 10 bar diameters. Heads with bearing areas and multiple configurations matching those permitted in practice are tested. A limited number of tests are also be performed on large-size hooked bars to determine if the relationship developed in previous tests, indicating that headed bar anchorage length equals approximately 80% of that for hooked bars, is appropriate for the largest size bars.
In addition to the previously noted project partners thanks to the companies contributing financial and material donations as well as technical support including BarSplice Products, Headed Reinforcement Corporation, nVENT Lenton, Commercial Metals Company, and Nucor Corporation.