Low-cycle fatigue life behaviour of BS 460B and BS B500B steel reinforcing bars

This paper investigates the low-cycle fatigue resistance of BS 460B and BS B500B steel reinforcing bars and proposes models for predicting their fatigue life based on plastic-strain (epsilon(ap)) and total-strain (epsilon(a)) amplitudes. Constant-amplitude, strain-controlled low-cycle fatigue tests were carried out on these bars under cyclic load with a frequency of 0.05 Hz. The maximum applied axial strain amplitude (epsilon(s,max)) ranges from 3 to 10% with zero and non-zero mean strains. The strain ratios (R = epsilon(s,min)/epsilon(s,max)) used are R = -1, -0.5 and 0. Hysteresis loops were recorded and plastic and total strain amplitudes were related to the number of reversals (2N(f)) to fatigue failure and models for predicting the number of reversals to fatigue failure were proposed. It is concluded that the predicted fatigue life of these bars is very accurate when compared with the measured experimental fatigue life results for wide range of values of strain ratios. It is also observed that based on plastic-strain amplitude, BS B500B consistently has a longer life (higher number of cycles to failure) than those of BS 460B for all R values; however, at low plastic-strain amplitudes they tend to behave similarly, irrespective of R value. Other observations and conclusions were also drawn.