Seismic Response Control of a Soft First-Story Building

A structure with a building plane 7.75 × 8.35 m, 47.8 m high, and having a height/width aspect ratio exceeding 6 has a building response that is difficult to control in both seismic and wind loading. We therefore changed the vibration mode from rocking to swaying by softening first-story translation stiffness and concentrating building deformation to make the first story energy-absorbing. The soft first-story structure we introduce involves (1) stiffening the structure above the second story, (2) making first-story columns laterally flexible and axially rigid, and (3) developing a response-hardening oil damper. The sections below detail these structural elements and dynamic response control performance against wind and seismic loading through time-history response analysis.