Seesaw-arm energy dissipation system with U-shaped steel dampers

This paper presents an investigation of the extended seesaw system using a seesaw-arm member with U-shaped steel dampers for improving the seismic energy dissipation in building structures. One of the notable features of the existing seesaw system is its usage of a quasi-linear motion mechanism, which allows the bracing members to remain tensile during vibration. In addition, a seesaw-arm concept is proposed for magnifying the damper deformation. Evaluation methods for the lateral stiffness and strength of the proposed system were derived. Then, cyclic loading tests were performed on six specimens, revealing that the proposed system has a stable hysteretic property and large energy-dissipation capacity. The accuracy of the stiffness and strength evaluation was assessed through comparisons with the test results. The evaluation of the displacement amplification factor of the damping system agreed well with the test results. Seismic-response analyses of five-story steel frame models adopting the proposed system were conducted. The maximum story drift angle, time-history responses of displacement and energy, and plastic-hinge formation were compared with those of the bare frame model. The analysis results revealed the efficiency of the proposed system for reducing seismic responses. Furthermore, a larger shape factor of the seesaw-arm member corresponded to better seismic performance.