Continuous Transverse Reinforcement — Behavior and Design Implications

Recent advancements in automatic reinforcing bar bending machines allow fabrication of continuous transverse reinforcement (CTR) with 90-degree transverse bends. The resulting closed, continuous reinforcement increases the speed by which transverse reinforcement can be placed, and can also improve structural performance. The ACI 318 Building Code (hereafter referred to as the “Code”) does not explicitly permit the use of CTR, although it is possible to receive approval based on sufficiently detailed supporting documentation. The research reported herein was conducted to evaluate performance of CTR in comparison to conventional transverse reinforcement (stirrup, tie, spiral, or hoop) for a wide range of loading scenarios. The data generated through this research provide background information necessary to modify the Code, such that CTR is recognized as an acceptable and economical alternative to conventional transverse reinforcement made in single pieces.

Evaluation of the experimental data from full-scale members and subassemblies showed current design provisions and detailing practices are applicable to CTR, and CTR can be used in lieu of conventional transverse reinforcement. Members and connections reinforced with CTR have better post-peak behavior, and generally higher strength and stiffness than comparable elements with conventional transverse steel. Nevertheless, the direction of applied torque in comparison to the direction in which CTR “spirals” is an important consideration and impacts the member performance. Recommendations and design equations for CTR are provided in this paper.

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