铅芯橡胶支座力学性能及其在桥梁工程中减、隔震应用研究.doc

铅芯橡胶支座力学性能及其在桥梁工程中减、隔震应用研究第25卷,第4期2004年8月中国铁道科学CHINARAILWAYSCIENCEV01.25No.4August,2004文章编号:10014632(2004)04013803?博士学位论文摘要?铅芯橡胶支座力学性能及其在桥梁工程中减,隔震应用研究吴彬,庄军生(博导)(铁道科学研究院,北京100081)关键词:桥梁;隔震;铅芯橡胶支座;力学参数;力学性能试验;地震响应分析中图分类号:U443.361文献标识码:A隔震技术在桥梁,建筑物等结构中的应用,可以明显提高结构的抗震性能.国外减隔震技术在桥梁上的应用已比较广泛,一些采用隔震技术的桥梁在地震中也已表现出良好的抗震性能.国内隔震技术在桥梁上的应用还很少,相关研究也不够系统,全面.对铅芯橡胶隔震支座及其在桥梁工程中的应用进行三方面的研究工作.1试验研究在不同频率,不同压应力,不同剪应变条件下,对不同构造的15组42个铅芯橡胶支座试件进行竖向及水平的静态,动态力学性能试验.系统研究支座形状系数,铅芯几何参数,个数及有效变形体积,橡胶几何参数及硬度,外加荷载的频率,正压力,剪应变等因素对支座各力学参数的影响.研究结果表明:铅芯橡胶支座的力学性能主要由其本身的构造及组成材料决定,外加荷载对其力学性能有一定的影响.铅芯橡胶支座的力学性能在往复加,卸载循环过程中具有较好的稳定性.对试验所得大量数据进行数学统计分析,建立铅芯橡胶支座各力学参数与其构造及外加荷载特性之间的一系列回归关系式.2铅芯橡胶支座隔震桥梁动力响应特性研究运用大型通用结构分析软件ANSYS,利用单收稿日期:20040309作者简介:吴彬(1965一),女,黑龙江齐齐哈尔人,副研究员.基金项目:铁道部科技研究开发计划项目(2000G029)墩模型,系统研究地震波,铅芯橡胶支座,桥梁下部结构及场地土特性对铅芯橡胶支座隔震桥梁地震响应的影响,得出以下结论.(1)铅芯橡胶支座对桥梁下部结构的减震效果主要取决于铅芯橡胶支座的屈服后刚度,且随屈服后刚度的减小而增大.铅芯橡胶支座对桥梁上部结构梁体的减震效果,随支座阻尼的增大而增大,上部结构梁体位移随支座刚度的减小而增大.在给定初始刚度及屈服后刚度时,墩,台处铅芯橡胶支座屈服力的总和与梁体重量的比值QW在一定范围内,支座对桥梁的减震效果最佳,建议Qw的取值范围应在4%10%之间.合理选择铅芯橡胶支座,可保证既降低墩顶位移,又不增大梁体位移,从而减小了桥梁下部结构的地震力,又满足了上部结构梁体之间抗震缝的要求.(2)铅芯橡胶支座对地震波频率较敏感.当地基较软或桥墩过柔时,铅芯橡胶支座的减震效果降低,甚至会加大结构的地震响应.建议将铅芯橡胶支座使用在桥梁下部结构刚度较大及刚性,一类和二类场地土上.(3)在地震作用下,铅芯橡胶支座双线性模型的刚度在弹性与屈服之间转换,阻尼也随屈服变形不断改变;而等效线性化模型的刚度与阻尼是定值.双线性模型更接近铅芯橡胶支座实际的滞回曲线.建议进行地震响应分析时,铅芯橡胶支座的分析模型采用双线性模型.(4)铅芯橡胶支座的减震效果明显优于板式橡第4期博士学位论文摘要139胶支座,特别是在大地震作用下,对梁体位移的控制,优势更明显.3全桥地震响应研究运用上述结论和本文回归公式设计铅芯橡胶支座,分别进行二类场地土上424m铁路简支梁隔震桥和330m城市轻轨连续梁隔震桥的顺桥向,横桥向地震响应分析.分析结果表明:设计的铅芯橡胶支座具有明显的减震效果,大幅度减小了各墩墩顶位移,墩底剪力及墩底弯矩,各墩所受地震力重新合理分配,各墩受力趋于均衡;在连续梁桥中,制动墩的减震率达80%以上;在简支梁桥中,各墩减震率达50%以上,各梁体的位移趋于协调,减小了台缝,梁缝宽度,避免了梁体间及梁体与墩台的碰撞.另外,不论简支梁桥还是连续梁桥,双向同时输入地震波,顺桥向和横桥向的地震响应基本没有相互影响.以上算例表明:试验所得经验公式可为铅芯橡胶支座的动力分析参数提供参考计算方法,也可为铅芯橡胶支座的构造设计提供依据.StudyonMechanicalCharacteristicsofLeadrubberBearingandItsApplicationforShockRuction/IsolationinBridgeEngineering(AbstractofthePh.D.Dissertation)WUBin.ZHUANGJunsheng(ChinaAcademy0fRailwaySciences,BeijingStructuralseismicperformanceofbuildingsandbridgescanbeimpmvedsignificantlybyapplyingseismicisolationtechnology.Thistechnologyhasalreadyfoundwideapplicationinmanyforeigncountries.Somebridgesusingseismicisolationtechnologyhaveperformedwellinactualearthquakes.InChina,fewbridgesUseseismicisolationtechnology.Relatedresearchesareneithercomprehensivenorsystematic.Inthisdissertation,thepotentialapplicationoflead-rub-betbearinginseismicisolationinbridgeengineeringisstudiedfromthreeaspects.1TestsAseriesofstatic/dynamicverticalandhorizontalmechanicalcharacteristictestswereconductedfor42lead-rubberbearingsin15groupswithdifferentstruc?turalparametersunderdifferentloadconditions,in-eludingdifferentfrequencies,compressivestresses,andshearingstrains.Theinfluenceofbearingshapecoefficient,leadgeometryparameters,numberofleadcores,effectiveleaddeformationvolume,rubberge-ometryparametersandhardness,externalloadingfre-quency,positivecompressionandshearingstrainon(Supervisor)100081,China)mechanicalpropertyparametershavebeenstudied.Theresultindicatesthatthemechanicalpropertiesoflead-rubberbearingmainlydependonitsstructureandmaterialcomponents,andareinfluencedbyitsloadconditiontoalesserextent.Thepropertiesarerea-sonablystableduringrepeatedloadingandunloading.Bymathematicalstatisticalanalysisofthetestdata,regressionformulashavebeenattainedforrelationsbetweenthemechanicparametersoflead-rubberbear-ingsandtheirstructuresandexternalloads.2DynamicresponsecharacteristicsofseismicisolatedbridgeswithleadrubberbearingUsingstructuralanalysissoftwareANSYS,theinfluenceofseismicwave,lead.rubberbearing,bridgeunderworkandsoilcharacteristiconanisolatedbridgeSresponsetoactualearthquakeshavebeensys-temicallystudiedwithasingle-piermode1.Thefol-lowingconclusionsareobtained.(1)Lead.rubberbearingsisolationeffectonthebridgeunderworkismainlydecidedbybearingSyieldstiffness.ItincreasesasbearingSyieldstiffnessde-creBses.BearingSisolationeffectonbeamincreasesas140中国铁道科学第25卷thedampingeffectofthebearingincreases.ThedisplacementofthebeamoftheupperstructureincreasesaSbearingsstiffnessdecreases.Whenbearingsinitialstiffnessandyieldstiffnessaregiven,bearingsisolationeffectonbridgeisoptimalwhenQyfW(theratioofbearingstotalyieldstrengthonpiertobeamsweight)isinacertainrange.4%一10%isrecommendedforthisrange.Therefore,aproperlyselectedleadrubberbearingcandecreasethedisplacementofpierstopwithoutincreasingbeamdisplacement,thusreducingtheseismicforceonthebridgeunderworkandsatisfyingtherequirementoftheseismicgapsbetweenbeamandbeam/abutment.(2)Leadrubberbearingisquitesensitivetoseismicwavefrequencyenbedrockorpieristoosoft,bearingsisolationeffectdecreasesandmayevenincreasebridgesresponsetoearthquakes.Therefore,itissuggestedtolimittheuseofleadrubberbearingtothebridgeunderworkwherestiffnessisbigenoughorinthecasewherethebridgeislocatedinrigid,Type1andType2bedrock.(3)Mfectedbyearthquake,thestiffnessofaleadrubberbearingdouble-linearmodelshiftsbetweenelasticityandyield.Dampnessalsochangeswiththeyieldingdeformation.Butthestiffnessanddampnessoftheequivalentlinearmodelofthelead.rubberbear.ingareconstant.Theleadrubberbearingsdouble-linearmodelprovidesacloserresulttoareallead.rub.berbearingshysteresisloop.Double-linearmodelisrecommendedaStheleadrubberbearinganalysismodelforanalyzingbridgesresponsetoearthquake.(4)Leadrubberbearingsisolationeffectisobviouslysuperiortoplatetyperubberbearing,especiallyincontrollingbridgesdisplacementduringmajorearthquakes3WholebridgesseismicresponseApplyingtheaboveconclusionsandregressionformulas,leadrubberbearingsweredesignedandseismicresponseanalysiswasmaderespectivelyfora424mrailwaysimply-supportedbeambridgeanda330murbanlightrailsuccessivebeambridgeonType2bedrock.Resultsdemonstratethattheleadrubberbearingshaveanobviousisolationeffect.Theysignificantlydecreasepiertopdisplacement,shearingstrengthandflexuralmomentofpierbottom.Earthquakeforceofeverypiertendstostrikeabalance.Insuccessivebeambridges,seismicisolationofbrakingpierisupto80%.Insimply-suppor