Damage-Free Wind-Restraint Device for a Base-Isolated Building Structure: Configuration and Prototype Test

For a base-isolated structure, a smaller stiffness of the isolation layer could better diminish the transmission of seismic energy from the foundation to the superstructure, thereby enhancing the base-isolation effectiveness. However, the reduction in isolation stiffness also prolongs the fundamental period of the structure, and it may lead to a heightened wind-induced floor acceleration in the superstructure and induce comfort issues. This conflict limits the applicability of the base-isolation technique in building structures situated in high seismic intensity and high wind load regions. In response to this conflict, this paper proposes a novel damage-free engagement device (DFED). The DFED is devised to provide additional lateral stiffness to the isolation layer under wind loads, enhancing the wind comfort of the superstructure, and to automatically retreat its stiffness under medium and large earthquakes, ensuring the flexibility and effectiveness of the base-isolation layer. The most salient feature of the DFED is that it is damage-free, which avoids the replacement of any components after strong earthquakes. Provided first in this paper are the configuration, working status, and assembly method of the DFED. The force–displacement relationship of the DFED is derived. To validate the mechanical behavior of the DFED, a series of DFED prototypes were manufactured and tested on a designated test bed. The experimental results proved that the DFED can provide stiffness under small displacements (corresponding to a wind-loading scenario) and withdraw its stiffness when the displacement surpasses a specific value (a medium or large earthquake takes place). The lateral stiffness of the vertical groove and the hardness of the engagement components are crucial for guaranteeing the expected mechanical behavior of the DFED.