Mechanical properties of electromagnetically adaptive friction pendulum bearings

To address the lack of uplift-restraining performance and adaptive isolation capability of ordinary friction pendulum bearings (FPBs), an FPB was combined with cuboid electromagnets and semi-active control theory was applied to develop an electromagnetically adaptive FPB (EAFPB). Theoretical formulas for the electromagnetic force and EAFPB model parameters were deduced, and a full-size EAFPB test specimen was designed. A displacement-electromagnetic force test was conducted on a cuboid electromagnet, and a compressive shear test was performed on the EAFPB to explore the effects of the working conditions on the mechanical properties of the EAFPB. A finite element model of the EAFPB was established to analyse its hysteretic characteristics and pull-out resistance under the same conditions that were applied in the experiments. The experimental results for the displacement and electromagnetic force of the cuboid electromagnets were consistent with the theoretical results, and the simulated EAFPB hysteresis curve agreed well with both the theoretical and experimental results. Under the same working conditions, the results for the EAFPB and ordinary FPB were compared, revealing that the unit energy consumption and equivalent stiffness of the EAFPB were significantly increased, by up to 66.95 % and 105.37 %, respectively. The equivalent damping ratio was reduced by up to 24.39 %. The cuboid electromagnets provided reliable and controllable pull-out resistance during EAFPB slip, with a maximum upliftrestraining resistance of 102.39 kN. By controlling the electromagnet current, the energy dissipation performance and uplift-restraining resistance of the EAFPB could be modified and adaptive control could be realised.