The Storey-isolated Limiting Deformation Experiment Analysis And Model Design Under Near-fault Ground Motions

Earthquake disaster is the focus of concern to the people of all countries for a long time.near-fault earthquake is far more destructive than the far-field earthquake,often caused huge casualties and property losses.The good effect of the isolated building in the earthquake is gradually recognized,to use rubber bearings for isolation is the most common method of isolation building.However,isolated buildings may overall collapse in the earthquake due to excessive displacement,but limit protection device can effectively solve the problem.In addition,due to the construction of its own structure or environmental reasons,the way of base isolation can not be achieved,instead of the story-isolation structure,which has a good effect either.Therefore,it is of practical significance to study the soft-collision on story-isolated structure under near-fault ground motions.This paper mainly studies from three aspects: isolation bearing,position limit device and shaking table model design.First of all,the author designed 10 small natural laminated rubber bearings,and through experiment to research the mechanical properties,includes compression properties' correlation of the compressive stress,and shear properties' correlation of shear strain,compressive stress,frequency of loading and repeated loading times.Then,the author designed 4 kinds of springs(48 in total),1 types of U-shaped 65 Mn steel limit device(3 in total)and UI combination limit device(3 in total),and have combine the experiment to analyze its property.At last,this paper designs a shaking table model test of soft-collision on story-isolated structure under near-fault ground Motions.According to the similarity ratio,the author designs a steel frame model with 5 layers,and the 12 experimental near-fault seismic wave are selected by ETABS,This paper introduces the installation scheme of isolation limit device and measuring device.The main conclusions are as follows:(1)The standard GB 20688.3-2006 given vertical stiffness calculation method does not apply to the smaller size rubber bearings,and measured values are quite different.The calculation method of shear stiffness is close to the measured value,which can provide reference.The vertical and shear stiffness has discreteness,therefore need to test before the shaking table isolation experiment.In principle,the similarity degree of shear stiffness is given priority.(2)With the increase of shear displacement,the shear stiffness of the rubber bearing is in a concave downward trend.With the increase of the vertical pressure,the shear deformation of the bearing has a small increase in energy dissipation,and the shear stiffness has no obvious change.The shear stiffness of the bearing is less affected by the loading frequency and the frequency of cyclic loading,can be ignored.(3)The tested spring stiffness is greater than the theoretical stiffness,for the first time after compression,the stiffness increased and the free height decreased.The U-shaped 65 Mn steel has two parts,which are elastic stage and plastic stage.The plastic stage stiffness decreases with the increase of displacement,the unloading stiffness is approximately equal to the load stiffness.The theoretical calculation is similar to the test results in elastic stage and plastic stage,the elastic limit displacement and the measured value are quite different,which need to be further modified.The curve of UI limiter is full,the energy dissipation capacity is increased,and the measured elastic stage stiffness and elastic limit displacement are larger than the theoretical value.(4)Through the ETABS test,it is found that the interlayer displacement angle of the structure is reduced by using the rubber bearing in seismic response.The shear deformation of the bearing is gradually decreased with the isolation layer moves upward.In shaking table test,we need to adjust the distance between structure and limit device,according to the position change of isolation layer and the actual response of the structure,to prevent the distance is not enough to have a good effect.This paper provides a reference for the study of mechanical properties of small rubber bearing,spring limiter,U-shaped 65 Mn steel limiter,UI limiter,and design of shaking table model,which provides a way for further research.