Mechanical properties of innovative prefabricated friction pendulum bearing with concrete-filled steel tube system

An innovative prefabricated seismic isolation system known as a friction pendulum bearing with a concrete-filled steel tube (FPB-CFST) was proposed to improve the mechanical performance and accelerate the construction process of the isolation layer. Unlike the traditional friction pendulum bearing-pier system, which consists of a cast FPB isolator and two cast-in-place reinforced concrete buttresses, the CFST was selected as the main supporting structure, and a spherical curvature surface (SCS) manufactured by a pressing process was attached to the CFST to slide the superstructure in the proposed FPB-CFST system. A construction procedure for the FPB-CFST was proposed, and a series of FPB-CFST specimens with various SCS radii were fabricated. The axial local compressive and compressive shear behaviors of the FPB-CFST were experimentally investigated. Friction coefficient tests were conducted to gain insight into the friction of the FPB-CFST. The mechanism of the proposed FPB-CFST subjected to axial local compression and compressive shear was discussed. The effects of sliding velocity and equivalent pressure of the bearing material on the friction coefficient were evaluated. The influences of the radius of the SCS and local compression ratio on the behavior of the FPB-CFST were addressed. The force model and design method of an FPB-CFST subjected to axial local compression and compressive shear are presented.