Design and performance evaluation of seismic isolation bearings with oblique viscous damper for protection of essential equipment and components

Earthquakes can significantly impact essential equipment and components, e.g., high-precision manufacturing equipment and valuable assets. Thus, one of the solutions is to install isolation bearings underneath essential equipment and components and to enhance seismic performance . Still, excessive isolation displacements may occur during large earthquakes, and additional damping devices are highly recommended to be installed along with the isolation bearings. This combination is often designed under design-level earthquakes, and the resulting performance may not be effective for under or beyond design-level earthquakes. Therefore, this research aims to establish a design method to achieve multiple performance objectives for isolation bearings with an oblique viscous damper to the horizontal direction at the equilibrium position and then to protect essential equipment and components. These multiple performance objectives consider comparable performance in the design-level earthquakes and higher reductions in isolation accelerations and displacements in the under and beyond design-level earthquakes, as compared to the conventional isolation system (i.e., the viscous damper parallel to the horizontal direction). In this study, a design method for single-curvature isolation bearings with an oblique viscous damper is developed using a stochastic linearization approach. This approach constructs a relationship among the nonlinear parameters (i.e., oblique angle, pin-to-pin length, linearly viscous damping coefficient) and linearized ones (i.e., stiffness parameter and damping coefficient), while the stochastic design method considers the nonstationary effects of earthquakes. These nonlinear parameters are consequently optimized to achieve multiple performance objectives against different levels of earthquakes. This study carries out several cases to demonstrate the design process and considers different initial oblique angles, pin-to-pin lengths, and damping coefficients. The performance of the proposed system with design parameters in actual earthquake scenarios is further evaluated numerically. Moreover, the dynamic characteristics and practical advantages of the proposed system are also investigated and discussed in the study. • An isolation system with geometrically nonlinear damping is experimentally verified. • A stochastic design method with multiple performance objectives considered is proposed. • The design method considered nonstationary earthquakes as the input. • The proposed design method was also numerically verified through 43 Meinong earthquake records. • The designed system more effectively reduced acceleration and displacement under below- and beyond-design-level earthquakes.