Normal and High-Strength Continuously Wound Ties
University of Cincinnati
January 2019 - March 2021
Bahram Shahrooz, Ph.D., P.E.
Ron Klemencic, MKA
Jack Moehle, U. of California, Berkeley
Neal Anderson, SGH
Reza Bayat, Englekirk
American Concrete Institute Foundation
Concrete Reinforcing Steel Institute Education and Research Foundation
The reinforced concrete construction industry increasingly is using continuously wound ties (CWT) constructed of a single piece of reinforcement. CWTs improve construction speed, and when made of High-Strength Steel can alleviate rebar congestion and reduce the total amount of reinforcement. The term CWTs can refer to either: (1) a circular or rectangular helical made of a single piece of reinforcing bar; or (2) a single hoop set with multiple legs made of a single piece of reinforcing steel. This research will focus on the second type. The current ACI 318 Code considers CWTs to be equivalent to a conventional hoop set made up of individual pieces of reinforcement. A performance better than conventional hoops is expected because most of the legs in CWTs do not need to rely on development length of hooked bars. Physical testing is needed to evaluate performance of CWTs (fabricated from ASTM A706 Grade 60 and ASTM A615 Grade 100) as well as their configuration limitations. It is likely that the expected improved performance may be considered in Code provisions, thereby reducing reinforcement quantities and congestion, enhancing confinement effectiveness in high-strength concrete (HSC), and improving the utilization of HSS.
Quarterly Progress Reports
Draft Final Report
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