A novel two-stage friction damper (semi-metal composite material) proposed and tested in the paper, some of which can be connected in parallel with regular isolation bearing to form a new composite type combined isolation bearing. It can significantly improve the matching of isolation parameters under multi-level earthquakes (helping to improve the applicability and sustainability of the structure) and enhance the isolation effect. Traditional methods, such as adding lead cores to laminated rubber bearings (LNR) to obtain LRB, or adding metal dampers, viscous dampers, etc., often encounter problems such as insufficient matching of isolation parameters (such as excessive slice force under frequent earthquakes and insufficient damping ratio under rare earthquakes), or space limitations due to the addition of dampers. To address these limitations, this paper proposes this new structure and uses the theory of elasticity mechanics to establish a set of methods for calculating the internal force and deformation of the damper, which can be used for the compact design of the internal structure and connecting components of the damper. After assembly and testing, it shows the damper can ensure reliable operation with a compact size and providing satisfactory damping performance. Independent mechanical performance tests confirm the shape characteristics of the force–displacement hysteresis curve, the appropriate preload torque value, and the technical parameters under variable displacement and variable speed loading conditions. The full-scale combined isolation bearing (LNRF) test verifies the working principle of the damper and the stable bone-shaped force–displacement hysteresis curve output, and compared with LNR, the equivalent viscous damping ratio increases by -14.8% (due to the increase in stiffness), 7.1%, 20.2%, and 24.0% at shear angles of 100%, 200%, 250%, and 300%, respectively. This indicates that the new combined isolation bearing structure and damper design method proposed in this paper can assist in the design of combined bearing structures and the development of products of various specifications, and suits for application in isolation buildings, bridges, and other engineering projects.
Gao et al. (Tue,) studied this question.