Low Cycle Fatigue Performance and Failure Analysis of Reinforcing Bar

Low cycle fatigue (LCF) behaviour and associated failure mechanisms of a thermo-mechanically treated Fe 500D steel rebar have been experimentally evaluated with a view to assess its performance under seismic condition. The total axial strain-controlled LCF tests have been performed at five different strain amplitudes (+/- 0.30 to +/- 1.00%) at ambient temperature until failure maintaining a constant true strain rate of 1 x 10(- 3) s(- 1)and a fixed strain ratio of - 1. Fatigue data have been analysed following both strain-life and plastic strain energy-life relationships; while, macro as well as micro features of the failed specimens, have been critically examined. These are supplemented by microstructural characterizations in addition to tensile and hardness measurements. Significant reduction of yield strength is recorded under dynamic loading which is responsible for considerable cyclic softening of rebar till failure in all strain amplitudes indicating the deterioration of seismic resistance property. Both strain-life and plastic strain energy-life relationships are found to accurately predict the cyclic plastic behaviour of the selected rebar. A near Masing behaviour is established by three different analytical approaches. The fatigue crack is always found to initiate at the transverse rib root and primarily propagates alongside the rim region.

Automated summary

The low cycle fatigue (LCF) behavior and associated failure mechanisms of a thermo-mechanically treated Fe 500D steel rebar were experimentally evaluated to assess its performance under seismic conditions. The results showed a significant reduction in yield strength under dynamic loading, leading to considerable cyclic softening of the rebar till failure in all strain amplitudes, indicating deterioration of seismic resistance property. Both strain-life and plastic strain energy-life relationships accurately predicted the cyclic plastic behavior of the selected rebar, with fatigue cracks always initiating at the transverse rib root and propagating primarily alongside the rim region.