期末考试试卷：抗震设计 - 土木工程 - 四川大学 Final Exam Paper: Seismic Design - Civil Engineering - Sichuan University

SeismicDesign

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Accordingtotheseismicdesignstrategy,thedesignobjectiveistonocollapse,noseverdamageunderrareearthquake.

Thesiteclassofabuildingisdeterminedaccordingtotheequivalentshearwavevelocityofsoilandthethicknessofoverlayinglayerofsite.

Thecharacteristicperiodofthesitedependsondesignearthquakegroupandsiteclass.

Inordertopreventbrittlefailureofframestructure,thedesignstrategyofstrongcolumnweakbeamandstrongshearweakbendingisproposed.

Therepresentativevalueofthegravityloadofabuildingisthecombinedloadvaluesfromdeadloadandvariableload.

Theseismiccapacityofabuildingmainlydependsontheperformanceofnodamageornorepair.

Oneofthedesignobjectivesinseismicdesignstrategyistonodamageornorepairunderfrequentrearearthquake.

Theinfluencingfactorsonthecharacteristicperiodofthesiteincludesiteclassanddesignearthquakegroup.

Sincebrittlefailureisstronglytobeavoidedforframestructureunderearthquake,thedesignstrategyofstrongcolumnweakbeamandstrongshearweakbendingisproposed.

Therepresentativevalueofthegravityloadofabuildingisthecombinedloadvaluesfromdeadloadandvariableload.

Theseismicloadingcarryingcapacityofabuildingmainlydependsontheperformanceofthemainlateral-force-resistingcomponents.

Abuildingwithdesignconditions:seismicprecautionaryintensity7anddesignbasicaccelerationofgroundmotion0.15g,themaximumvalueofhorizontalseismicinfluencecoefficientunderfrequentearthquakeis0.12.

Inordertopreventbrittlefailureofframestructure,thedesignstrategyofstrongcolumnweakbeamandstrongshearweakbendingisproposed.

Therepresentativevalueofthegravityloadofabuildingisthecombinedloadvaluesfromdeadloadandvariableload.

Theseismiccapacityofabuildingmainlydependsontheperformanceofthemainlateral-force-resistingcomponents.

Abuildingwithseismicdesigncondition:seismicprecautionaryintensity8anddesignbasicaccelerationofgroundmotion0.30g,themaximumvalueofhorizontalseismicinfluencecoefficientunderfrequentearthquakeis0.24.

Thesoiltypeofabuildingismedium-stiffsoilandthethicknessofoverlayinglayeris15m.Thesiteclassissiteclass2.

A125mtallreinforcedconcretebuildingwithintensity7,whichstructuralsystemshouldbechosen?Tubestructural.

AframestructureassignedtoseismicgradeIandintensity8,theenhancementcoefficientofthemomentofcolumnendtorealizetheconceptof“strong-columnweak-beam”is----1.7.

Theseismicloadingcarryingcapacityofabuildingmainlydependsontheperformanceofthemainlateral-force-resistingcomponents.

Abuildingwithdesignconditions:seismicprecautionaryintensity7anddesignbasicaccelerationofgroundmotion0.15g,themaximumvalueofhorizontalseismicinfluencecoefficientunderfrequentearthquakeis0.12.

Thesiteclassforabuildingsitewithmedium-softsoilandthethicknessofoverlayinglayer20misGroupII.

A70mtallreinforcedconcretebuildingwithprecautionaryintensity7,whichstructuralsystemshouldbechosen?Subcolumnseismicwallstructure.

AgeneralframestructureassignedtoseismicgradeIunderintensity8,theenhancementcoefficientofshearatbeamendtorealizetheconceptof"strong-shearweak-bending”is–1.7.

Ifthecenterofstiffnessandthecenterofmassforasinglestorybuildingdonotcoincide,thebuildingwillexhibittorsionalvibrationunderhorizontalseismicaction.

TrueandFalse

Accordingtotheseismicdesignstrategy,oneofthedesignobjectivesisnottoallowanystructuraldamageunderfrequentearthquake.[False]

ThecharacteristicperiodofthesiteTisindependentoftheseismicintensity.[True]

TheseismicmeasuresofseismicgradeIVcomponentaremorestrictthanthatofseismicgradeI.[False]

Whenthecenterofmassandthecenterofstiffnessdonotcoincide,thebuildingwillhavetorsionalvibrationunderhorizontalgroundmotion.[True]

Thehigherthelateralstiffnessofthestructureis,thehigheritsseismicductilityis.[False]

MultipleChoiceQuestion

ACategoryBbuildingwithdesigncondition:seismicprecautionaryintensity7anddesignbasicaccelerationofgroundmotion0.15g,thepeakvalueofhorizontalseismicinfluencecoefficientunderrareearthquakeis:

0.72

Thesoiltypeofabuildingismedium-softsoilandthethicknessofoverlayinglayeris20m.Thesiteclassis:

II

A105mreinforcedconcretebuildingwithintensity8(0.2g),whichstructuralsystemshouldbechosen?

Tubestructure

AframestructureassignedtoseismicgradeIandintensity9,theenhancementcoefficientofthemomentofcolumnendtorealizetheconceptof“strong-columnweak-beam”is:

1.7

Whichfactorisnotmainlyrelevanttoseismicconceptualdesign?

Precautionaryseismicintensity

Question-Answer

Pleasediscusshowthestructuralperformancesunderminor,moderate,andstrongearthquakesshouldbeforagoodseismicdesignedbuilding.Besides,howtorealizeitduringthedesignprocess?

Answer:Foragoodseismicdesign:

Minorearthquakes:Thestructureshouldremainelasticwithnodamage.

Moderateearthquakes:Itshouldexhibitelastictoelastic-plasticbehavior,withlimitedandrepairabledamage.

Strongearthquakes:Elastic-plasticbehaviorisacceptable,allowingforseverebutcontrolleddamagewhilepreventingcollapse.

Designprocessrealization:Thisisachievedusingatwo-stageseismicdesignprocess:

Elasticanalysistoensurenodamageduringminorandmoderateearthquakes.

Conceptualdesignanddetailingmeasurestohandlestrongearthquakes,suchasductilityreinforcementandenergydissipationmechanisms.

Whatarethehazardsofsoilliquefactiontobuildings?Pleasedescribetheprocessofsoilliquefactiondiscrimination.

Answer:Hazardsofsoilliquefaction:

Groundrupture,unevensettlement,andtiltingofbuildings.

Structuraldamagesuchascracksinwalls,beams,andjoints.

Sinkingorfloatingofequipment.

Discriminationprocess:

Preliminaryevaluation:Basedonsoiltype,groundwaterlevel,andgeologicalage.

Fineevaluation:UsingtheStandardPenetrationTest(SPT)toassesssoilpropertiesanddetermineliquefactionpotential.

Pleasedescribethemainprocedureswhenusingthemodalresponsespectrummethodtodeterminethehorizontalseismicactions.

Answer:Basedonthehorizontalseismicinfluencecoefficientα(T),theprocedurestocalculatetheseismiceffectsusingthemodalresponsespectrummethodare:

Performmodalanalysis,calculatethenaturalperiodsTj(Tj=2πωj)andmodeshapesXjofthefirstmodes.

DetermineαforthefirstmodesusingTjandζj.

Calculatethemodalparticipationfactorγj.

CalculatetheseismicactionFji=αjγjXjGi.

Fjiactingonthestructure,calculatetheseismiceffectsSjbystaticmethods.

Calculatetheoverallseismiceffectsusingthecombinationofmodes.

Pleasediscusshowtorealizetheductileabilityinseismicdesignofreinforcedconcretestructures.

Answer:

Useconfinementreinforcementincriticalregions,suchascolumnends.

Selecthigh-ductilitymaterialstopreventbrittlefailure.

Employstrong-columnweak-beamdesigntoensureenergydissipationoccursinbeams.

Includeproperdetailingtoenhanceinelasticdeformationcapacity.

Whatistheseismicresponsespectrum?Whatparametersaffecttheseismicaccelerationresponsespectrum?Pleasedrawtheschematicdiagramofthedesignseismicspectrum.

Answer:Theseismicresponsespectrumrepresentsthepeakresponse(displacement,velocity,oracceleration)ofastructureasafunctionofitsnaturalperiodunderaspecificgroundmotion.

Influencingparameters:

Sitecondition.

Dampingratio.

Earthquakemagnitudeandintensity.

Schematicdiagram:(Refertoastandardaccelerationvs.periodgraphwithpeaksfordifferentdampingratios.)

Foragoodseismicperformanceofabuilding,howthestructureisexpectedtobehaveunderminor,moderate,andstrongearthquakes?Besides,howtorealizeitduringtheseismicdesignprocess?

Answer:

Minorearthquakes:Elasticbehavior,nodamage.

Moderateearthquakes:Elastictoelastic-plasticbehavior,minorrepairabledamage.

Strongearthquakes:Elastic-plasticbehavior,severedamagewithoutcollapse.

Useatwo-stagedesigncombiningelasticanalysisandrobustdetailing.

Stage1:Theloadingcarrycapacityanddeformationdemandsaredeterminedfromelasticanalysisaccordingtofrequentearthquake,whichnormallysatisfieslevels1and2.Thelevel3requirementismetthroughconceptualdesignanddetailingmeasures.Formoststructures,designwithstage1isproper.

Stage2:Forthespecialstructureunderrareearthquakes,stage2conductstheelastic-plasticanalysis,sothattomeetthethirdleveloffortificationrequirements.

Pleasediscusswhyseismicconceptualdesignisalsoimportantinseismicdesign.Alsolistsomeaspectsreflectingseismicconceptualdesign.

Answer:Seismicconceptualdesignensuresbetterperformanceduringearthquakesbyfocusingonsimplicity,symmetry,andproperloaddistribution.Itreducesrisksofvulnerabilitiesthatarehardtoaddresslater.

KeyAspectsofSeismicConceptualDesign:

Clearanddirectloadpathsensureseismicforcesareefficientlytransferredtothefoundation.

Simplicityandsymmetryindesignminimizetorsionanddistributeforcesevenly.

Avoidirregularitiesinstiffness,mass,orgeometrytoeliminatediscontinuities.

Incorporateductilitytoallowdeformationwithoutfailure,dissipatingseismicenergy.

Useproperframingsystems,suchasshearwallsorbracing,tomanagelateralforceseffectively.

Strongcolumn-weakbeam,strongbeam-weakcolumn.Whichtypeofbuildingstructuresyouprefertodesignandconstruct?Explainbriefly.

Answer:Ipreferdesigningandconstructingstructureswithastrong-columnweak-beamconfiguration.Thisapproachenhancesseismicsafetybyensuringthatplastichingesforminthebeamsratherthanthecolumnsduringstrongearthquakes.Beamscandissipateseismicenergythroughcontrolleddeformation,whilethecolumnsmaintaintheverticalload-bearingcapacity,preventingoverallstructuralcollapse.

Conversely,astrong-beamweak-columndesignismorevulnerablebecausecolumnfailurecanleadtoprogressivecollapse,posingagreatersafetyrisk.Therefore,thestrong-columnweak-beamconceptprovidesbetterductility,energydissipation,andstructuralresilienceunderseismicforces.

Whatisthestrongcolumn-weakbeamprinciple?Pleaseexplain.

Answer:TheStrongColumn-WeakBeamprincipleinstructuralengineeringdictatesthatcolumnsshouldbestrongerandstifferthanbeams.Thisensuresthatinseismicevents,thebeamswillabsorbanddeflectstresseswhilethecolumnsremainintact,maintainingthestructure'sstability.Theprinciplehelpscontrollateralloaddistribution,preventingthecolumnsfromfailingunderextremestress.Bydesigningcolumnstobestronger,thisapproachmitigatestheriskofcatastrophiccollapseduringanearthquake.

Explaintheresponsespectrummethodforseismic