| The isolation technology has the advantages of simple mechanical model,clear mechanism and obvious shock absorption effect,therefore,it has become the most widely used and most mature damping technology.Although the isolated structure can greatly reduce the dynamic response of the superstructure and ensure the safety of the structure under the fortification intensity,due to the randomness of the earthquake,ultra fortification intensity earthquake happens from time to time.Under ultra fortification intensity earthquake,excessive horizontal displacement of the isolation layer will be generated,which causes failure of the isolation bearings and causes the overturning and collapse of the superstructure.Therefore,it is necessary to protect the isolation layer by soft collision limit,and limit the horizontal displacement of the isolation bearing to the extent permitted by the specification to ensure the safety of the isolated structure under the action of super-intensity earthquake.The research contents of the soft collision limit system of the isolated structure are as follows:(1)A new type of limit protection device is designed and developed.The limit protection device is simulated by ABAQUS finite element software.The vertical compression analysis adopted by the displacement-control loading method is carried out to understand the mechanical properties and deformation process of the limit protection device.And the stiffness values of the limit protection device at different displacement stages are obtained.(2)The specimens of different sizes of full-scale limit protection device are made by cold bonding,and the load-displacement curve of the specimen under compression was obtained through the compression properties test adopted by the displacement-control loading method.The test results show that the full-scale limit device has automatic resetting ability,variable stiffness and has certain energy dissipation capacity,which consistent with the initial design conception and meets the basic requirements of the soft collision limit protection device.(3)ETABS is used to establish 3D finite element model of base-isolated structure.The superstructure is an elastic model and the fortification intensity is 7 degree(0.15g).Firstly,the dynamic responses analysis of the base-isolated structure under rare earthquake of 7 degree(0.15g),8 degree and 8 degree(0.30g)is carried out.Then,the Gap element is use to simulates a soft collision between the isolated structure and the limit protection devices.the dynamic responses analysis of the base-isolated structure with limit protection device under earthquake of 8 degree(0.30g)is carried out.The effect on the inter-story shear force,interstory displacement,the acceleration at the top of the superstructure and displacement of the isolation layer is compared and analyzed.(4)When analyzing in the ETABS software,the limit protection device adopts the “threefold line” stiffness elastic model,which does not consider the hysteresis characteristics of the limit protection device and the change of the stiffness of the desending part of loaddisplacement curve.In order to further study the effect of the limit protection device on the dynamic responses of base-isolated structures.Firstly,the formula is fitted to the experimental results,and a "triangular" elastoplastic model is proposed.The elastoplastic model is simulated by the Simulink module provided by MATLAB.The accurate and fast solution of elastic-plastic restoring force are realized by input structural displacement.Then,a multi-particel model of the base isolated structure is established,the non-degenerate Bouc-Wen elastoplastic model is adopted for the isolation layer and the suppertructure,and the "triangle" elastoplastic model is adopted for the limit protection device.The soft collision of the limit protection device and the base-isolated structures are simulated by the Simulink module.Finally,the dynamic responses analysis of the base-isolated structure and the base-isolated structure with limit protection device under earthquake is carried out.The effect on inter-story shear force,inter-story displacement,the acceleration at the top of the superstructure and the displacement of the isolation layer is compared and analyzed. |
