Numerical investigation of earthquake response reduction effects by negative stiffness connection for adjacent building structures

Coupled vibration control (CVC) for adjacent buildings can mitigate the seismic response of the system by properly setting the structural parameters, including the connecting elements. However, optimization of the control effect for CVC structures may be limited when using only positive or zero stiffness at the connecting spring. The present study explores the control effectiveness by passive negative stiffness as a connecting element installed between the mainframe and subframe of CVC structures. A two-degrees-of-freedom (2DOF) model representing a coupled building, which consisted of the mainframe and subframe linked by a spring and a viscous damping element, was used. The transfer function (TF) for displacement and acceleration of the mainframe and subframe was evaluated under various structural parameters. The results showed that by setting an optimal negative stiffness and an optimal damping at the connecting portion, the peak amplitude of the TF of the mainframe was significantly reduced compared to that of reference-controlled case without negative stiffness (i. e., with only a damping element). In addition, adopting negative stiffness in CVC structures can extend the range of optimal tuning conditions. Moreover, a time history earthquake response simulation was conducted using 2DOF models with different natural periods and structural parameters subjected to various input motions, including simulated waves and observed records. The results indicate that use of the negative stiffness connection can effectively reduce the seismic response of the mainframe for passive CVC structures.