Low-Cycle Fatigue Performance of High-Strength Steel Reinforcing Bars

New high-strength reinforcing steel bars (HSRB) are under development in the United States, driven by constructability and economic and environmental incentives. An experimental study was undertaken to compare the low-cycle fatigue behavior of the HSRB with that of benchmark Grade 60 (420 MPa) bars. HSRB obtained from two mills using the main two production methods in the United States were tested. Other variables treated in this study were bar strength, bar size, loading protocol, and bar unsupported length. The study indicated significant departures between the fatigue life of high-strength and regular-strength bars and uncovered correlations between the fatigue life of bars and various bar parameters, including deformation geometry and chemical composition. The correlations suggest that simple adjustments to manufacturing processes may lead to significant improvements in fatigue life of HSRB. The study results also provide important data for developing material specifications for a seismic grade of HSRB.

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