SIMPLIFIED ANALYSIS AND NUMERICAL SIMULATION OF DOUBLE VARIABLE CURVATURE FRICTION PENDULUM ISOLATION BEARING

The development process of Variable Curvature Friction Pendulum Isolation Bearing (VCFP) and Double Concave Friction Pendulum Isolation Bearing (DCFP) is reviewed, combined with the advantages of those two bearings, a new style bearing called Double Variable Curvature Friction Pendulum Isolation Bearing (DVCFP) is proposed in this paper. Based on the principle of mechanical equilibrium, the simplified analysis study on the DVCFP whose sliding surfaces are made of two types of functions is carried on, the stiffness of each DVCFP are derived, their recovery mechanisms are also discussed, and the computing formulas of residual displacement are obtained as well. Moreover, the models with solid element of each DVCFP which contains Double Variable Frequency Pendulum Isolation Bearing (DVFPI) and Double Conical Friction Pendulum Isolation Bearing (DCFPI) are built by using ABAQUS software, the hysteretic property under low cyclic loading is simulated, the contrastive analysis on the ability of energy dissipation of friction pendulum bearing (FPB), DCFP, VCFP and DVCFP are carried on according to the effective viscous damping ratio and coefficient of energy dissipation. Finally, the recovery characteristic of DVCFP is also discussed by simulation. The results show that: (1) the numerical simulation results are in accordance with those of the simplified analysis; (2) the hysteretic property of DVCFP is favorable because of its plump hysteretic curves, further more, comparing with FPB, DCFP and VCFP, its effective viscous damping ratio and energy dissipation coefficient are higher, which reveal its greater ability in energy dissipation; (3) the maximum allowable displacement of this bearing is larger than FPB and VCFP in the same size, which offers preferable guarantee for making effective use of isolation; in addition, compared with FPB and DCFP, the stiffness and frequency of the DVCFP can decrease with the increment of bearing displacement through appropriate design, therefore, the low frequency resonance problem of isolated structures can be well solved; (4) in comparison with FPB, DCFP and VCFP, the stiffness of DVCFP is smaller so that the shear transferred to the superstructure is smaller; (5) the residual displacement of DVCFP is depended on both friction coefficients and the parameters of sliding surface functions up and down, parametric design is necessary in order to control the value in an acceptable range in engineering.