| Isolation Technology has been widely used in engineering structures because of its obvious effect of shock absorption and simple mechanical model.Although isolation structures can effectively reduce the dynamic response of superstructure,due to the randomness of earthquakes,sudden super-strong earthquakes occur from time to time,Under the action of super strong earthquake,the isolation bearing is very likely to cause the damage of the building structure due to the excessive horizontal displacement,endangering the safety of human life and property,Therefore,it is necessary to set a soft-impact limit protection device as the second line of defense in the isolation layer to limit the horizontal displacement of the isolation bearing within the allowable range.The results show that the limiting effect of isolation layer can be effectively improved by optimizing the performance parameters of the limiting device.In this paper,the experimental study and performance parameter optimization analysis of the flexible limit protection device for base-isolated structures are as follows:(1)In this paper,the finite element simulation model of base isolation structure is established by using ETABS software,and the base isolation design is carried out to study the dynamic response of structure under fortification intensity.The results show that the isolation system can effectively prolong the natural vibration period of the structure,ensure the safety of the structure,and the stress of the isolation bearing and the horizontal displacement of the isolation layer meet the requirements of the code,The inter-story shear force,inter-story displacement angle and top-story acceleration of the superstructure of the isolation system are much smaller than those of the aseismic system,and the isolation effect is remarkable.(2)Based on the new type of flexible limit protection device,the finite element software ABAQUS is used to simulate and analyze the compression deformation performance of the device.On this basis,four specimens of limit protection device with the same size and different materials were made by thermal vulcanization,and the compression performance tests with displacement amplitudes of 40mm and 60mm were carried out,and it is concluded that the limit protection device has the characteristics of nonlinear stiffness and automatic reset ability,and can meet the limit requirement of the isolation layer,finally,the nonlinear elastic model of the device is fitted.(3)The three-dimensional model of ETABS is transformed into the equivalent two-dimensional series multi-particle model,and the structure is simulated with the Simulink module of MATLAB.Firstly,the initial distance of the limit protection device is set to240mm,with 4 on each side.The dynamic response of the structure under 9 degree rare earthquake(PGA=6.2m/s~2)is studied.The results show that after the soft collision between the limit protection device and the structure,the inter-story displacement angle of the upper structure increases inevitably,and the displacement of the isolation layer decreases to a certain extent,but it is not controlled within the safe range,there is still a problem of low limit rate,so it is necessary to optimize the performance parameters of limit protection device in order to achieve better limit effect.(4)Genetic Algorithms is used to optimize the design of limit protection device,which is aimed at the displacement of isolation layer and the displacement angle of upper structure layer,the limiting effect of limit protection device on isolated layer under 9 degree rare(PGA=6.2m/s~2)and 8 degree(0.30g)super rare(PGA=8.4m/s~2)earthquakes is studied.The results show that the displacement of the isolated layer can be limited in the safe range by soft collision between the optimized displacement device and the structure,and the displacement angle of the upper structure is smaller than that of the aseismic structure,which still has a certain isolation effect,the structural response can meet the requirements of the code. |
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