Numerical experimental and theoretical investigation of reinforced concrete elements with rectangular spiral rebar for multi-behavior analysis

Rectangular Spiral Rebar (RSR) is an innovative alternative to conventional ties, offering simplified construction and enhanced performance in reinforced concrete (RC) members. Despite its advantages, a comprehensive evaluation of RSR under multi-behavioral loading conditions (compression, shear, and seismic) remains unexplored. This study integrates numerical, experimental, and theoretical approaches. Numerical models were developed using Abaqus, SAP2000, and VecTor2 to assess RSR performance under static (compression/shear), lateral quasi-static, and seismic loads (five intensity levels). Experimentally, 14 RC short columns with RSR were tested under monotonic compression, varying cross-sectional geometries (rectangular/square) and reinforcement configurations. The Mander confined concrete model was extended to incorporate RSR, refining predictions for longitudinal rebar, cover concrete, and core concrete behavior. RSR increased compressive strength by 8.4% compared to conventional ties, with more uniform stress distribution. Nonlinear finite element analysis (VecTor2) accurately predicted crack patterns, though computational models and standards (e.g., SMCFT, MPLANE, CEB-FIP, CSA, AASHTO) overestimated shear capacity. RSR confinement produced blunter crack patterns. RSR-confined frames exhibited 8% lower drifts under high-intensity ground motions (PGA = 0.52 g) and required 12% less transverse reinforcement. The proposed theoretical method showed high accuracy (average experimental-to-theoretical capacity ratio: 1.03 for RSR specimens). This study bridges critical gaps in RSR research, demonstrating its multi-behavior efficacy in improving strength, constructability, and seismic resilience. The validated analytical model provide a foundation for code adoption and practical applications.