Seismic behavior of repairable columns with UHPC segments and replaceable buckling-restrained energy dissipaters

Minimizing earthquake damage and improving repair efficiency are the main principles of resilient structures. The present study proposed a repairable column with UHPC segments and replaceable internal buckling-restrained energy dissipaters. In the UHPC replacement segment, the buckling-restrained energy dissipaters were connected to rebars in other segments through threaded sleeve couplers and could be replaced after an earthquake event. The connected dissipater was unbonded to prevent premature low cycle fatigue failure. A UHPC transition segment was designed to prevent plastic hinge shifting. To evaluate the structural performance of the proposed column, cyclic loading tests were performed on two repairable columns using normal-strength dissipaters or hybrid high-and normal-strength dissipaters before and after repairing. The test results showed that compared with RC columns, the proposed columns exhibited significantly greater strength, deformation capacity, and energy dissipation, as well as low stiffness degradation. Use of high-strength dissipaters improved the strength and energy dissipation, but decreased the deformation capacity. After replacing the dissipaters and cover UHPC, the strengths and energy dissipation of the repaired columns slightly decreased, while the ultimate displacements were almost the same, showing satisfactory seismic resilience. Further, a stress-strain model for the unbonded buckling-restrained energy dissipaters and a flexural strength model for the original and repaired columns were proposed, which were compared with the existing test results.