Soft Collision Behavior Of Base-isolated Structure Based On The Elastoplastic Model Of Horizontal Stop Blocks

Under the action of strong earthquake or near-fault pulse-like ground motion,the base-isolated structure may have excessive displacement deformation,leading to the tilt instability of the overall structure or the hard collision with the surrounding foundation pit.To limit the horizontal displacement of the isolation layer,an elastoplastic model of horizontal stop blocks with double broken line is designed through the differential Bouc-Wen model,which forms a composite system of energy dissipation and shock absorption with the isolation bearings,and the secondary reinforcement of the base-isolated structure is completed by soft collision.Firstly,SAP2000 is selected to establish the dynamic analysis model.The frame of steel structure is transformed into the base-isolated structure and simplified into a bar system model.The Gap element and Plastic（wen）element are connected in series to simulate the initial gap and elastoplastic model of horizontal stop blocks,and the near-fault pulse-like ground motion is input to calculate the main pulse dynamic response of the isolated structure under free vibration and soft collision.Then,the structural properties such as mass,stiffness and damping of the above model are extracted,and the multi-particle simulation model is established on the Simulink platform.The Bouc-Wen model is used to consider the nonlinear deformation of the isolation layer,the superstructure and the displacement-constraint device,and the near-fault pulse-like ground motion is input to calculate the dynamic response of the isolated structure under free vibration and multiple soft collisions.The results show that the base-isolated structure with soft collision has both displacement-constraint effect and dynamic amplification effect.Under the ideal single soft collision,the yield strength and elastic stiffness of the elastoplastic model of horizontal stop blocks show a good positive correlation with the maximum interlayer displacement angle of the upper structure.When multiple soft collisions occur,the positive correlation is disturbed to some extent,and the local correlation is negative.Finally,based on the Simulink simulation model,the high-dimensional point selection method and the spectral representation method are used to artificially simulate the fully non-stationary ground motions to study the energy dissipation effect of the elastoplastic model of horizontal stop blocks and the dynamic response characteristics of the base-isolated structure under soft collision.The results show that when the yield strength ratio α_y of the displacement-constraint device is close to the elastic stiffness ratio α_k,the yield strength plays a major role,and the elastic stiffness plays a certain control role.When both of them are large enough,the disturbance of soft collision on the upper structure is more intense,which may stimulate the high-order vibration mode of the structure,or lead to nonlinear deformation of the floor components and show a ladder-like inter-story displacement time history curve,and permanent inter-story displacement residual deformation occurs.