Seismic Performance of a Single-Story Articulated Steel Structure System

Abstract

An innovative articulated steel frame system consisting of continuous beams, columns, and end plates with gap bolts is proposed in this study. The gap bolts are untightened with initial gaps and used to connect beam flanges with column end plates, enabling the frame to rock freely at the initial state and avoid overturning of the whole frame when the initial gaps of bolts are exceeded. The proposed system can switch between a free-rocking column system and a rigid-jointed frame when subjected to strong excitations. Recentering of the structure is provided only by gravity loads without the addition of post-tensioning elements. This system with additional damping elements is expected to be a highly efficient seismic control system in which a high-mode effect can be mitigated through multiple-rocking interfaces along the structural height direction. As a fundamental study, this paper focuses on a single-story articulated steel frame without additional damping devices. An analytical model is established, and small shaking table tests are conducted. The effects of structural parameters and excitations on the seismic performance of the proposed system are investigated. Responses of the corresponding rigid steel frame are compared with those of the proposed system in both time and frequency domains. A method based on the seismic energy spectrum is proposed to estimate free-rocking uplifts within the initial gaps. A finite element model is also established to simulate dynamic responses. The analytical and numerical results are compared with the experimental results with acceptable accuracy. This study is of significant importance for similar rocking column systems and further study on corresponding controlled multiple-rocking systems.