Low Cycle Fatigue Performance and Failure Analysis of Reinforcing Bar
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Low Cycle Fatigue Performance and Failure Analysis of Reinforcing Bar Md Abu Bakkar1 · Rajib Saha2 · Debdulal Das1 Received: 13 June 2020 / Accepted: 29 July 2020 © The Korean Institute of Metals and Materials 2020
Abstract 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 straincontrolled 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 × 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. Keywords Low cycle fatigue · TMT rebar · Strain–life · Strain energy · Failure mechanism
1 Introduction Reinforcing bar, commonly referred to as rebar, is the essential strengthening element of the reinforced concrete structures like buildings, flyovers, bridges, dams, concrete roads, industrial and underground structures etc. The rebars carry tensile while concrete only withstands compressive part of the loading in steel reinforced concrete structure. Rebars also carry and distribute load apart from controlling the displacement of the structure; therefore, these are known as the backbone of the reinforced concrete structures [1]. In the case of an earthquake, the brittle concrete rapidly cracks under severe ground motion, and consequently, full load is transferred to the rebars. These rebars then experience dynamic loading with huge tension and compressive strain reversals [2–5]. The failure of rebars thus leads to * Debdulal Das [email protected]; [email protected] 1
Department of Metallurgy and Materials Engineering, Indian Institute of Engineering Science and Technology, Shibpur, Howrah, West Bengal 711103, India
Research and Development Division, TATA Steel India, Jamshedpur, Jharkhand 831001, India
2
catastrophic disintegration of entire structure causing a lot of causalities and colossal losses. Several factors for instance cracking, excessive buckling and corrosion leads to failure of rebars. One of the prime design c
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