Isolation Device Of Tension Pull Friction Pendulum And Its Isolation Effect Analysis

As people pay more attention to structural seismic safety,the isolation technology is receiving more and more attention and has been applied more and more.Structural base isolation is mainly to set an isolation layer between the foundation and the superstructure.By arranging isolation bearings on the isolation layer,the horizontal natural vibration period of the superstructure can be extended,the excellent frequency range of ground motion can be avoided,and the seismic force transmitted to the superstructure can be reduced.The common types of bearings for structural base isolation are laminated rubber bearings and friction pendulum bearings.The friction pendulum bearings are of great concern because their isolation period is not affected by the change of superstructure mass.At present,the friction pendulum type seismic isolation bearings commonly used in the field of structural isolation are separated from each other,and the bearings can only be pressed,but usually do not have the pull-out resistance function.However,the vertical displacement of bearing under seismic load will increase the risk of structural overturning,which limits the application range of friction pendulum isolation bearings.Based on this background,this paper proposes a friction pendulum isolation device with pull-out resistance function,and studies the effectiveness of the bearing through finite element analysis and other methods.The main work of this paper is as follows:1.a new type of pull-out isolation bearing is proposed,its geometric structure design is completed,the equivalent parameter calculation formula of the pull-out isolation bearing is derived,and the theoretical hysteretic model is analyzed.The hysteretic curve of the support obtained by simulation is relatively full,which shows that it has good energy dissipation effect,and the whole is in good agreement with the theoretical hysteretic model,which proves the correctness of the theoretical restoring force model and the equivalent formula.The vertical mechanical properties of each component of the bearing under compression and tension conditions are obtained through static analysis.The bearing has good compression resistance and certain pull-out resistance,and has the ability to resist deformation,which meets the design index of the bearing.Under the action of vertical cyclic displacement,the tensile hysteretic curve of the bearing does not change significantly,and the tension and displacement are linear,indicating that the material is not yielding,and the overall tensile effect of the bearing is stable.2.the friction pendulum bearing is designed based on the actual tensile demand of the project.According to the vertical bearing capacity,horizontal isolation capacity and self resetting capacity,the allowable displacement of the bearing is 150mm,the compressive bearing capacity is 4000kN,the tensile bearing capacity is 600kN,and the cycle is 2.75s.The size parameters of each part of the device can be determined.According to the specification,the friction material is 7mm thick PTFE plate.Determine the force transmission path.According to the design value of bearing capacity,the material strength of steel and PTFE plate can be checked and calculated to meet the specification requirements.3.carry out the dynamic time history analysis of the effectiveness of the tensile pullout isolation bearings,select the typical frame structure,establish the finite element model,arrange the tensile pull-out isolation bearings,carry out the dynamic time history analysis,and compare the results with the traditional isolation bearings with the same isolation period.Compared with the traditional friction pendulum isolation bearing,the maximum vertical pulling displacement of the tension device is reduced from 0.203mm to 0.107mm under rare earthquakes,which reduces the interlayer displacement difference of the isolation layer and the risk of building overturning.The maximum vertical tension of the anti pull friction pendulum is 145.33kN,which is equivalent to the equivalent tensile stress of the rubber bearing with the same vertical bearing capacity of 0.52MPa,meeting the design value of the device.Compared with the non isolated structure,the isolated structure with tension pull friction pendulum bearings controls the amplification of floor acceleration.With the increase of PGA and floor,the difference of horizontal peak acceleration gradually increases.The maximum inter story displacement angle of the isolated structure with tension pull friction pendulum bearings occurs in the isolation layer,and the sliding displacement of the friction pendulum is less than the allowable displacement limit,which can ensure its safe operation.With the increase of floors,the story to story displacement angle of the isolated structure is significantly smaller than that of the non isolated structure,which can be reduced by 68%,indicating that the tensile pull-out friction pendulum isolation bearing can reduce the displacement response under earthquake.The isolation effect decreases with the increase of friction coefficient,and increases with the increase of equivalent radius of curvature and PGA.