Matching relationship of low-cycle fatigue life and fatigue design method of concentrically braced frames with H-section steel

Simulations on 192 concentrically braced frames with H-section steel (Q355B) are carried out to investigate their low-cycle fatigue performance. The fatigue life of a steel-braced frame is predicted using a multiaxial fatigue damage parametric model. To depict the fatigue failure sequence and the matching relationship of the fatigue life between the two components in the braced frame, the fatigue life ratio (β) is introduced. This ratio represents the gusset plate's fatigue life to the brace's fatigue life. Simulated results are analyzed, and β is found to be positively correlated with four influencing factors, the width-to-thickness ratio of the brace flange, connection coefficient, ratio of the column length to beam length, and slenderness ratio of the gusset plate. Also, β is found to be negatively correlated with the slenderness ratio of the brace. Based on the Bayesian updating method, a probabilistic model is formulated to predict β of a steel-braced frame. Accordingly, a fatigue design method is proposed, which contributes to avoiding the in-coordination of seismic capacity caused by the significant difference between the brace's and gusset plate's fatigue life within the steel braced frame. The proposed fatigue design method has the potential to serve as a reference for improving design specifications.