Numerical simulation of the hysteretic behavior of unbonded steel plate brace encased in reinforced concrete panel

Based on experimental studies of unbonded steel plate brace encased in reinforced concrete panel, hereafter referred to as panel of buckling restrained brace (panel BRB), finite element analysis of the behavior and hysteretic characteristics of panel BRB has been carried out by using the ABAQUS software, with the effects of clearance and friction between the hole of the panel and the brace on the working behavior of panel BRB taken into account. The analysis and test results indicate that the panel BRB specimens with small and uniform clearance as well as desirable reinforcements exhibit good ductility and stable hysteretic behavior. With the increase in compressive force of the core steel brace, the number of small amplitude flexural buckle waves of the brace also increases. The results also reveal that, with the increase of clearance, the punching shear force of the core brace to the panel increases because of the increase in the amplitude of the buckling waves of the brace. Axial force of the compressive brace is variable along its length when friction appears between the brace and the panel, and the length of buckle waves is smaller where the axial force of brace is larger. Meanwhile, the tangent stiffness of panel BRB is enhanced by the friction, and under compression the tangent stiffness of the specimens with larger clearance is larger than that of the specimens with smaller clearance when clearance is within the specified range. In addition, the punching shear force of the brace to the panel can be decreased and therefore the panel BRB may acquire better ductility when size of the clearance is determined with the proposed formula.