Low-cycle fatigue life prediction of I-shaped steel brace components and braced frames

Abstract

Four methods (seven models) are extended and applied to the low-cycle fatigue life prediction of steel brace, including the ductile damage method, the equivalent strain method, the critical plane method, and the representative strain method. Using these models, the fatigue life of 53 steel brace components and 5 bracing members in single diagonal braced frames is predicted and compared with the measured life in experiments. Thus, some useful information on the accuracy and reliability of different methods is provided. Based on a parametric sensitivity analysis, the ductile damage model can represent the fracture process of the brace and has a good application on fatigue life prediction, especially when the fatigue life is less than 60. The equivalent strain method overestimates the fatigue life while the critical plane method underestimates the fatigue life. The fatigue parameters of steel Q235B in these two life prediction methods are obtained. The proposed representative strain method compensates for the fact that the fiber model cannot consider the effect of local buckling on the fatigue life of the bracing member. This method has good accuracy and computational efficiency on fatigue life prediction.