QUASI-STATIC TESTING OF CORE-TUBE BOX-COLUMN STEEL FRAMES WITH DOUBLE FLANGED RIGID CONNECTIONS

This paper proposes two types of box-column steel frames with double flanged rigid connections, namely, the plane core-tube frame and the damped core-tube frame. Correspondingly, two prototypes of 5-story structures were designed. Quasi-static testing on 0.7-scale subsystems was conducted following a pseudo-dynamic test of the subsystems. Structural properties including the hysteretic performance, strain variations of typical members, degradation of structural stiffness, energy dissipation are analyzed and compared. The results indicate that both frames remain elastic while the intermediate columns with friction dampers consume 71.3% of the dissipated energy in the building at the stage of 0.005 rad. (1/200) interfloor drift. As the drift reaches the threshold of 0.02 rad. (1/50) of the elastoplastic angles of steel structures, the hysteretic curves of the two substructures are bilinear. The panel zones of the connections remain elastic. Plasticity of a column base of the damped frame develops more slowly than that of the plane frame. As the drift ratio goes to 0.04 rad. (1/25), the areas of the hysteretic curves are enlarged without plastic deformation in the panel zones. The base buckling of the plane frame is severer than that of the damped frame. The connections of the two frames are reliable. The intermediate column with friction dampers effectively restrains the plasticity development in the damped frame through frictional energy dissipation in the quasi-static test. The stiffness, energy-dissipation capacity and seismic performance of the damped frame are much better than those of the plane frame.