鉛芯橡膠支座力學(xué)性能及其在橋梁工程中減、隔震應(yīng)用研究.doc

鉛芯橡膠支座力學(xué)性能及其在橋梁工程中減、隔震應(yīng)用研究第25卷,第4期2004年8月中國鐵道科學(xué)CHINARAILWAYSCIENCEV01.25No.4August,2004文章編號:10014632(2004)04013803?博士學(xué)位論文摘要?鉛芯橡膠支座力學(xué)性能及其在橋梁工程中減,隔震應(yīng)用研究吳彬,莊軍生(博導(dǎo))(鐵道科學(xué)研究院,北京100081)關(guān)鍵詞:橋梁;隔震;鉛芯橡膠支座;力學(xué)參數(shù);力學(xué)性能試驗;地震響應(yīng)分析中圖分類號:U443.361文獻(xiàn)標(biāo)識碼:A隔震技術(shù)在橋梁,建筑物等結(jié)構(gòu)中的應(yīng)用,可以明顯提高結(jié)構(gòu)的抗震性能.國外減隔震技術(shù)在橋梁上的應(yīng)用已比較廣泛,一些采用隔震技術(shù)的橋梁在地震中也已表現(xiàn)出良好的抗震性能.國內(nèi)隔震技術(shù)在橋梁上的應(yīng)用還很少,相關(guān)研究也不夠系統(tǒng),全面.對鉛芯橡膠隔震支座及其在橋梁工程中的應(yīng)用進(jìn)行三方面的研究工作.1試驗研究在不同頻率,不同壓應(yīng)力,不同剪應(yīng)變條件下,對不同構(gòu)造的15組42個鉛芯橡膠支座試件進(jìn)行豎向及水平的靜態(tài),動態(tài)力學(xué)性能試驗.系統(tǒng)研究支座形狀系數(shù),鉛芯幾何參數(shù),個數(shù)及有效變形體積,橡膠幾何參數(shù)及硬度,外加荷載的頻率,正壓力,剪應(yīng)變等因素對支座各力學(xué)參數(shù)的影響.研究結(jié)果表明:鉛芯橡膠支座的力學(xué)性能主要由其本身的構(gòu)造及組成材料決定,外加荷載對其力學(xué)性能有一定的影響.鉛芯橡膠支座的力學(xué)性能在往復(fù)加,卸載循環(huán)過程中具有較好的穩(wěn)定性.對試驗所得大量數(shù)據(jù)進(jìn)行數(shù)學(xué)統(tǒng)計分析,建立鉛芯橡膠支座各力學(xué)參數(shù)與其構(gòu)造及外加荷載特性之間的一系列回歸關(guān)系式.2鉛芯橡膠支座隔震橋梁動力響應(yīng)特性研究運(yùn)用大型通用結(jié)構(gòu)分析軟件ANSYS,利用單收稿日期:20040309作者簡介:吳彬(1965一),女,黑龍江齊齊哈爾人,副研究員.基金項目:鐵道部科技研究開發(fā)計劃項目(2000G029)墩模型,系統(tǒng)研究地震波,鉛芯橡膠支座,橋梁下部結(jié)構(gòu)及場地土特性對鉛芯橡膠支座隔震橋梁地震響應(yīng)的影響,得出以下結(jié)論.(1)鉛芯橡膠支座對橋梁下部結(jié)構(gòu)的減震效果主要取決于鉛芯橡膠支座的屈服后剛度,且隨屈服后剛度的減小而增大.鉛芯橡膠支座對橋梁上部結(jié)構(gòu)梁體的減震效果,隨支座阻尼的增大而增大,上部結(jié)構(gòu)梁體位移隨支座剛度的減小而增大.在給定初始剛度及屈服后剛度時,墩,臺處鉛芯橡膠支座屈服力的總和與梁體重量的比值QW在一定范圍內(nèi),支座對橋梁的減震效果最佳,建議Qw的取值范圍應(yīng)在4%10%之間.合理選擇鉛芯橡膠支座,可保證既降低墩頂位移,又不增大梁體位移,從而減小了橋梁下部結(jié)構(gòu)的地震力,又滿足了上部結(jié)構(gòu)梁體之間抗震縫的要求.(2)鉛芯橡膠支座對地震波頻率較敏感.當(dāng)?shù)鼗^軟或橋墩過柔時,鉛芯橡膠支座的減震效果降低,甚至?xí)哟蠼Y(jié)構(gòu)的地震響應(yīng).建議將鉛芯橡膠支座使用在橋梁下部結(jié)構(gòu)剛度較大及剛性,一類和二類場地土上.(3)在地震作用下,鉛芯橡膠支座雙線性模型的剛度在彈性與屈服之間轉(zhuǎn)換,阻尼也隨屈服變形不斷改變;而等效線性化模型的剛度與阻尼是定值.雙線性模型更接近鉛芯橡膠支座實際的滯回曲線.建議進(jìn)行地震響應(yīng)分析時,鉛芯橡膠支座的分析模型采用雙線性模型.(4)鉛芯橡膠支座的減震效果明顯優(yōu)于板式橡第4期博士學(xué)位論文摘要139膠支座,特別是在大地震作用下,對梁體位移的控制,優(yōu)勢更明顯.3全橋地震響應(yīng)研究運(yùn)用上述結(jié)論和本文回歸公式設(shè)計鉛芯橡膠支座,分別進(jìn)行二類場地土上424m鐵路簡支梁隔震橋和330m城市輕軌連續(xù)梁隔震橋的順橋向,橫橋向地震響應(yīng)分析.分析結(jié)果表明:設(shè)計的鉛芯橡膠支座具有明顯的減震效果,大幅度減小了各墩墩頂位移,墩底剪力及墩底彎矩,各墩所受地震力重新合理分配,各墩受力趨于均衡;在連續(xù)梁橋中,制動墩的減震率達(dá)80%以上;在簡支梁橋中,各墩減震率達(dá)50%以上,各梁體的位移趨于協(xié)調(diào),減小了臺縫,梁縫寬度,避免了梁體間及梁體與墩臺的碰撞.另外,不論簡支梁橋還是連續(xù)梁橋,雙向同時輸入地震波,順橋向和橫橋向的地震響應(yīng)基本沒有相互影響.以上算例表明:試驗所得經(jīng)驗公式可為鉛芯橡膠支座的動力分析參數(shù)提供參考計算方法,也可為鉛芯橡膠支座的構(gòu)造設(shè)計提供依據(jù).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中國鐵道科學(xué)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