Sliding U-shaped steel damper for multi-directional displacement

A U-shaped steel damper may undergo multi-directional displacements. However, U-shaped energy-dissipation plates with large width-to-thickness ratio may experience unexpected torsional deformation during an out-of plane displacement and provide an unstable restoring force and energy dissipation. Discussed here is a sliding U-shaped steel damper that uses connecting structures to obtain force-free sliding in out-of-plane directions. Cyclic performances under multi-directional displacements were verified experimentally, and out-of-plane force-free sliding was observed. The energy-dissipation plates only exhibited in-plane plastic deformation and provided a stable restoring force as well as energy dissipation. Equations for the yield and ultimate restoring forces were developed by considering the loading angle, and a finite element model in ABAQUS reproduced physical tests. Connection structures were thus improved for higher stiffness, and lateral sliding that considered the peak vertical force was also proposed. Finally, an analytical hysteretic model for the sliding U-shaped steel damper was abstracted based on the test and simulation results, which shows acceptable agreement with the test results.