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Title: Normal- and High-Strength Continuously Wound Ties

Author(s): Malory R. Gooding, Elizabeth A. Mosier, and Bahram M. Shahrooz

Publication: Structural Journal

Volume: 120

Issue: 6

Appears on pages(s): 73-84

Keywords: ACI 318; axial loading; confined concrete; ductility; highstrength reinforcement; hoops; seismic detailing; special boundary elements (SBEs); transverse reinforcement

DOI: 10.14359/51739017

Date: 11/1/2023

Advancements in steel reinforcement bending machines have allowed for the fabrication of continuously wound ties (CWTs). CWTs are being used in place of conventional transverse reinforcement to reduce waste and construction time and to alleviate congestion. A total of 20 reduced-scale special boundary elements (SBEs), using Grade 60 and Grade 80 conventional hoops and CWTs, were tested under uniaxial compression to evaluate the performance of members with CWTs. All the specimens exceeded ACI nominal axial strength capacity at zero eccentricity calculated using the measured material properties and ignoring reduction factors. The CWT specimens exhibited improved post-peak ductility compared to conventional hoops when all the current ACI requirements for SBE transverse reinforcement were satisfied. Post-peak ductility was further enhanced by using Grade 80 CWTs in conjunction with 10 ksi (69 MPa) concrete. Confined concrete strengths from three well-established models were reasonably close to the measured values; however, all the models were found to overestimate post peak ductility regardless of the type of transverse reinforcement.