Torsion Effect On The Isolated Structures During Seismic Input Motion

The research and application of structure vibration control has broadprospect.A qualitative leap has been achieved by structured fortificationmeasures to control wind.resistant design of civil and structuralengineering earthquake,which produced enormous economic and socialbenefits.The passive control one of the base isolation,which is wide-spreadly concerned and become a hotspot of research and development,ismore effective,safe,dureable,applicable.The torsion impact of theearthquake is often ignored when we analyse research base isolationsystem.while through disaster investigation and tests,theoreticalanslysis.we recognized that structure not noly can producetranslational vibration but also torsional vibration,even torsionalvibration may be the main factor that cause building damage.Currently,the research of the torsional response of isolated structureis little done.It is necessary to research the torsional response ofisolated structure.In this article,we consider structure eccentricityand torsional vibration component by which what effcets will be induce.This dissertation analyzes the model of translational motion andtorsional motion coupling reaction of the isolated structures,vibrationequation,and the principle of generating torsion vibrationwave.Structural dynamic anslysis program is written in Matlab ALGOLand a three.tier isolation frame sturcture work as an example.the analysisshowed that:when the eccentricity of the upper part of the structure andthe isolation layer is less than30%,the eccentricity of the isolationlayer has a large impact on the torsion angel of the isolation layer.whilenot on the torsion angle of the upper structure,and not on the displacementof the isolation layer and the upper structure.The eccentricity of theupper structure has a little impact on the torsion angel and displacement of the isolation layer,while has a larger impact on thetorsion angle and displacement of the upper structure and the more largereccentricity,the more larger layer torsion angle and displacement.Theeccentricity of the isolation layer has a significant impact on thetorsion angle of the upper structure of the layer when the upper structureeccentricity is small.The eccentricity of the isolation layer will havea smaller impact on the upper structure torsion angle of the layer whenthe eccentricity of the upper structure.Seismic wave spectrumcharacteristics have a relatively obvious impact on structureresponse.And using the matlab software programmed to generate the torsionwave,the results show that the torsion around z direction or around ydirection of the isolated structure might make the bearing plastic.butthe bearing displacement is less1.2mm.Compared to input around z axisand y axis,translational x.axis to isolated structure,translationalx.axis inputing to the sturcture will let the displacement reduced orincreased.but the magnitude will be between-2.5%~2.5%.The displacementof the structure of inputing around z.axis or around y.axis divide thedisplacement of the structureof inputing around z.axis、around y.axisand translational x.axis,the value is less than10%,the torsionalresponse of isolated structure induced by the torsion around z directionis more critical than by the torsion around y direction.