土木工程--毕业设计外文翻译(原文+翻译)

毕业设计（论文）外文翻译题目西北物流中心2号楼设计专业土木工程班级土木074学生指导教师二零一零年Low-coherencedeformationsensorsforthemonitoringofcivil-engineeringstructuresD.Inaudia,A.Elamarib,L.Pfluga,N.Gisinb,J.Breguetb,S.Vurpillota“IMAC,LaboratoryofStressAnalysis,SwissFederalInstituteofTechnology,CH-1015Lausanne,Switzerland‘GAP,GroupofAppliedPhysics-OpticalSeciion,GenevaUniversityCH-1205Geneva,SwitzerlandRcccivcd25January1993;inrevisedform8March1994;accepted25March1994AbstractAnoptical-fiberdeformationsensorwitharesolutionof10pmandanoperationalrangeof60mmhasbeenrealized.Thesystemisbasedonlow-coherenceinterferometryinstandardsingle-modetelecommunicationfibers.Itallowsthemonitoringoflargestructuresoverseveralmonthswithoutnoticeabledrift.Nocontinuousmeasurementisneededandthesystemisinsensitivetovariationsofthefiberlosses.Thistechniquehasbeenappliedtothemonitoringofa20mX5mX0.5m,120tonconcreteslaboversixmonths.Itispossibletomeasuretheshrinkageofconcreteanditselasticcoefficientduringpre-straining,givingreproducibleresultsingoodagreementwiththeoreticalcalculationsandmeasurementsperformedonsmallconcretesamples.Thispaperdescribestheopticalarrangementandtheproceduresusedtoinstallopticalfibersinconcrete.Keywor&:Ikformationsensors;Civil-engineeringstructures1.IntroductionBoththesecurityofcivil-engineeringworksandthelawrequireaperiodicmonitoringofstructures.Themethodsusedforthispurpose,suchastriangulation,waterlevelsorvibratingstrings,areoftenoftediousapplicationandrequireoneormanyspecializedoperators.Thiscomplexityandtheresultingcostslimitthefrequencyofthemeasurements.Furthermore,thespatialresolutionisoftenpoorandtheobservationisusuallyrestrictedtothesurfaceoftheobject.Thereisthusarealdemandforatoolallowinganinternal,automaticandpermanentmonitoringofstructureswithhighaccuracyandstabilityoverperiodstypicallyoftheorderof100yearsforbridges.Inthisframework,fiber-opticsmartstructures(i.e.,structureswithself-testingcapabilities)aregaininginimportanceinmanyfieldsincludingaeronauticsandcompositematerialmonitoring.Thistechnologycanbeappliedincivilengineeringandinparticularfortheshort-andlong-timeobservationoflargestructuressuchasbridges,tallbuildingframes,dams,tunnels,roads,airportrunways,domes,pre-stressingandanchoragecables.Themonitoringofsuchstructuresrequiresthedevelopmentofameasuringtechniquewithhighaccuracy,stabilityandreliabilityoverlongperiods.Ithastobeindependentofvariationsinthefiberlossesandadaptedtotheadverseenvironmentofabuildingsite.Toreducethecostoftheinstrumentation,itisfurthermoredesirabletousethesameportablereadingunitforthemonitoringofmultiplestructures.Wedescribehereasystembasedonlow-coherenceinterferometryrespondingtoalltheserequirements.2.ExperimentalarrangementThemeasuringtechniquereliesonanarrayofstandardtelecommunicationopticalfibersinmechanicalcontactwithconcrete.Anydeformationofthehoststructureresultsjnachangeintheopticallengthofhefibers.Eachsensorlineconsistsoftwosingle-modeibers:onemeasurementfiberinmechanicalcontactwiththestructure(gluedorcemented)andareferenceiberplacedloosenearthefirstone(inapipe)inordertobeatthesametemperature.Sincethemeasurementtechniquemonitorsthelengthdifferencebeweenthesetwofibers,onlythemechanicaldeformationwillhaveaneffectontheresultswhileallotherperurbations,suchasthermallyinducedchangesintherefractiveindexofthefibers,willaffectthetwoinanidenticalwayandcanceleachanotherout.Tomeasuretheopticalpathdifferencebetweenthetwofibers,alow-coherencedoubleinterferometerintandemconfigurationhasbeenused(Fig.1)[l].ThesourceisanLED(light-emittingdiode)workingaround1.3pmwithacoherencelengthL,of30pmandaratedpowerof200pW.Theradiationislaunchedintoasingle-modefiberandthendirectedtowardthemeasurementandthereferencefibersbymeansofa50:50single-modedirectionalcoupler.Attheendsofthefiberstwomirrorsreflectthelightbacktothecoupler,wherethebeamsarcrecombinedwitharelativedelayduetothelengthdifferenceAL,betweenthefibers,andthendirectedtowardsthesecond(reference)interferometer.ThereferenceinterferometerisofMichelsontypewithoneofthearmsendedbyamobilemirrormountedonamicromctricdisplacementtablewitharesolutionof0.1pmandanoperatingrangeof50mm.ItallowstheintroductionofanexactlyknownpathdifFcrenceAL,betweenitstwoarms.Thisfiberinterferometerisportableandneedsnoopticaladjustmentaftertransportation.IthasbeendevelopedbytheGAPwiththesupportoftheSwissPTTforopticalcabletesting[2].Theintensityattheoutputofthereferenceinter-ferometerismeasuredwithapig-tailphotodiodeandisthengivenby[3]wherezz,,ristheeffectiverefractiveindexofthefiber,zzgthegrouprefractiveindex(about1%higherthannefrinsilica),A,thecentralvacuumwavelengthofthelight,zi,,theautocorrelationfunctiontakingthespectralcharacteristicsoftheemissionintoaccountandALthephysicalpathdifferencebetweenthetwointerferingpaths.FurthersimilarinterferencetermsappearinEq.(1)inthespecialcaseswhenAL,L,orAL,L,.Whentheopticalpathdifferencebetweenthearmsinthereferenceinterferometercorrespondstotheoneinducedbythetwofibersinstalledinthestructure(withinthecoherencelengthofthesource),interferencefringesappear.ScanningAL,with