Experimental study on continuous energy-dissipative steel columns under cyclic loading

This paper proposes a continuous energy-dissipative column (CEDC) system to improve the seismic resilience of framed structures. The CEDC system consists of two steel boundary columns connected by a series of replaceable steel strip dissipators (RSSD). The dual columns are continuous along the height of buildings and are connected by a rigid link at each storey level. The CEDC system is designed as a dual-function structural component under earthquake where inelastic deformation concentrates in the RSSDs, while the boundary columns remain elastic and sustain the gravity loads. Three full-scale cyclic loading tests are carried out to investigate the seismic behavior of CEDC systems and replaceability of RSSDs. The specimens differ in the distance between the dual columns, thickness and number of RSSDs, and loading schemes. The experimental results show that the proposed CEDC system has good load-bearing capacity and energy dissipation capacity. The equivalent damping ratios of all the specimens reach 0.4 for a storey drift ratio of 1/30. It was found that the boundary columns are in elastic when the steel strips first yield. The failure of CEDC systems is due to the ductile rupture of RSSDs rather than lateral or lateral-torsion buckling in them. Finite element models of CEDC systems are established and validated against experimental results. Parametric studies are carried out to investigate the effect of axial loads in the boundary columns on the seismic behavior of CEDC systems. The numerical results show that the ultimate capacity and post-yield stiffness of CEDC systems reduces as the axial load ratio increases due to the second order effect of gravity load. A simplified method to determine the design axial load ratio of CEDC under gravity loads is proposed and validated.