Numerical analysis on steel bracing members with bolted gusset plate connections

Damage models for steel bracing members with bolted gusset plate connections were established and validated against experimental data. This paper aims to enhance understanding of the hysteretic performance and force mechanism of bracing members with bolted gusset plate connections via numerical models, aiding in the optimization of their design for improved safety and economy. These models accurately predict low-cycle fatigue life, damage progression, and fracture locations. In this study, internal force distribution on connection plates or angle steels gradually decreases from the center towards both ends. The angle steel or connection plate on the compressive brace flange side is more prone to damage than those on the tension brace flange side. Bracing members with bolted connections were found to have longer fatigue life compared to those with welded connections. Approximately 45% of total energy dissipation is attributed to friction energy from bolt slippage, reducing the internal energy proportion from plastic deformation and delaying member cracking. Stress analysis on gusset plates revealed highest stress level at the corner, with welded connections experiencing higher hot spot stress than bolted ones. The effectiveness of the uniform force method and modified AIJ (Architectural Institute of Japan) method in designing brace connections was assessed. Finally, parameter studies explored the effects of geometric factors (brace slenderness ratio, clearance and brace angle) on loading capacity, energy dissipation, low-cycle fatigue life, and gusset plate stress. Increasing brace slenderness ratio significantly enhances low-cycle fatigue life in bolted connections, while brace angle and clearance have minimal impact on it.