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Extremely Low Cycle Fatigue Behaviors of Anti-Seismic Steel HRB400 Reinforcing Steel Bars under Strong Earthquakes

Luo Yun-Rong, Wang Qing-Yuan, Fu Lei, Xie Wen-ling and Zhang Ying-Qian

The extremely low cycle fatigue (ELCF) behaviors of anti-seismic steel HRB400 reinforcing steel bars were comprehensively studied following the cyclic push-pull loading tests with extremely high strain amplitudes (up to ±12.8%). The cyclic stress response characteristics and cyclic stressstrain relationships were investigated. The cyclic response characteristics were closely related to the strain amplitudes, and the secondary hardening phenomenon appeared under some strain amplitudes. The strain-life data from the axial tests were used to derive suitable Coffin-Manson parameters for the test material. The scanning electron microscope (SEM) morphology revealed ELCF damage mechanisms were distinctive of those typical from LCF. Compared with the common low-cycle fatigue (LCF) fracture region, several unique features in the ELCF regime can be noticed, including the deviations of the fatigue life from the Coffin-Manson law and the transformation of fatigue cracking modes.