Low-cycle fatigue behaviour and strain-life model of stainless steel reinforcing bars

Reinforced concrete (RC) structures, often subjected to repeated static and dynamic loadings, are prone to fatigue failure of their steel reinforcing bars (rebar), which is worsened by corrosion in high chloride concentration service environments. Stainless steel rebars have gained increasing attention in recent years as a promising alternative to traditional carbon steel rebars to overcome chloride-induced corrosion, with life cycle costs and life cycle analyses affirming their sustainability and economic benefits. This paper reports the results of a pioneering series of 125 low-cycle high-amplitude fatigue tests on 12 mm hot-rolled and cold-rolled austenitic EN 1.4301 and 16 mm hot-rolled duplex EN 1.4482 stainless steel reinforcing bars as well as B500C 12 mm and 16 mm carbon steel reinforcing bars under different strain amplitudes 1%-5% and different bar length-to-diameter ratios 5-15. Strain-life models in the form of Coffin-Manson and Koh-Stephen relationships were developed and calibrated based on the low-cycle fatigue test data. Furthermore, empirical relationships relating the rebar slenderness to the ductility coefficient and exponent of the strain-life models were presented. An increase in both the slenderness and strain amplitude was found to reduce the fatigue life for all tested rebar materials. The hotrolled stainless steel rebars exhibited superior fatigue performance in terms of fatigue life and energy dissipation than B500C carbon steel rebars. For the stainless steel rebars, cold-rolling was found to reduce the fatigue life. However, the cold-rolled stainless steel rebars of the smallest tested slenderness were still found to have comparable fatigue performance as the carbon steel rebars.