1、Nonlinear FEAnalysis of RC Frames Infilled with RCWalls for Seismic Retrofitting in DIANAFEAElpida Georgiou-PhD CandidateSupervisor-Professor Christis Chrysostomou21 November 2017DepartmentDepartment of of CivilCivil EngineeringEngineering andand GeomaticsGeomaticsCUT is a a newnew statestate Univer
2、sityUniversity in Cyprus Growing within the historical city center of LimassolCUT was founded in 2004 and welcomed its first students in 2007 Offers academic degree programs at all levels(Undergraduate,Masters,PhD)17 Undergraduate Programs of Study 32 Graduate Programs of StudyTheThe facultyfaculty
3、of of EngineeringEngineering andand TechnologyTechnology Department of Electrical Eng.Computer Engineering and Informatics Department of Mechanical Eng.And Materials Science and Engineering Department of Civil Engineering and GeomaticsCYPRUS UNIVERSITY OF TECHNOLOGYGeneral dataThe youngest among the
4、 leadingYoung Universities in EuropeCyprus University of Technologybetween 350-400 in the world202 in EuropeIn less than 10 yearsOverviewResearch purposeProcedureExperimental studyGeometry,design,tests,resultsModel in DIANAFEAGeometry definition,elements,mesh,material models,loads,analysisDIANAFEAre
5、sults comparison with experimental resultsOutcomesFurther workDIANA FEA WebinarResearchPurposeStrengtheningStrengthening ofof existingexisting structuresstructures withwith RCRC infillsinfills withinwithin existingexisting framesframes Limitations in design and construction regardingthis method furt
6、her investigation is required Aparametric study is necessarySimulationSimulation ofof a a full-scalefull-scale Ps-DPs-D testtest in inDIANADIANA FEAFEA Numerical experiments Global&Local resultsContributionContribution ofof shearshear connectorsconnectors(dowels(dowels)Important component of the ove
7、rall shearresistance capacity of RC Not been yet analyzed adequately Complicated mechanism Not clear how to design themDIANA FEA WebinarOriginal FrameRetrofitted FramePrototypePrototype modelmodel-SERFIN project-Full-scale case study-Model correctly reflectsthe real situation-Results&dataDIANAFEAfor
8、DIANAFEAforsimulationsimulation-FEM of the frame torepresent the experiment-Validation with experimentalresults-Nonlinear hystereticbehavior of materials at thelocal level-Capture and evaluate thebehavior of RC infillsProcedureReliableReliable studystudy ofof anyanybuildingbuilding parameterparamete
9、r-Numerical experiments andparametric studiesDIANA FEA WebinarExperimentalstudySERIESSERIESS Seismic E Engineering R Research I Infrastructures of E European S Synergies European Commission,Framework Programme 7SERFINSERFIN projectSeSeismic R Retrofitting of RC F Frames with RC InInfilling First tim
10、e in the world a full-size test of this type of specimen 18 months(December 2013 July 2015)European Laboratory of StructuralAssessment(ELSA)of the Joint Research Centre inIspra(Italy)Important Experimental results&DataStructuralStructural EngineeringEngineering InternationalInternational JournalJour
11、nal ofof IABSE,IABSE,23(2),23(2),159-166,159-166,(2013)(2013)-http:/ ScientificScientific andand TechnicalTechnical ResearchResearch Reports,Reports,(2013)(2013)-https:/ec.europa.eu/jrc/en/publication/eur-scientific-https:/ec.europa.eu/jrc/en/publication/eur-scientific-and-technical-research-reports
12、/seismic-retrofitting-rc-frames-rc-infilling-serfin-project-series-transnational-accessand-technical-research-reports/seismic-retrofitting-rc-frames-rc-infilling-serfin-project-series-transnational-accessParticipants:Participants:Cyprus University of Technology CoordinatorUniversity of Nantes(France
13、)University of CyprusDENCO Design&EngineeringConsultants(Greece)DIANA FEA WebinarThespecimen-geometryMulti-storeyMulti-storey 4-storeys Total specimen height 12m-excluding the foundation Storey height 3mMulti-bayMulti-bay 3-bays Centre-line length of thespecimen was 8.5mRCRC infillinginfilling 2 end
14、 exterior frames only Spaced at 6m Linked by a 0.15m thick RC slaband 4 transverse beams 35x65 RC infill wall has the samethickness as the width of theframe members(0.25m)Central bay 2.5m/Two exteriorbays 3m(centre to centre)Columns 25x40,Beams 25x50DIANA FEA WebinarEASTEASTWESTWESTSOUTHSOUTHWALLWAL
15、LDesignDesign standardstandardTypical building inthe 70s-80s inCyprusNo specific design standardNo provisions forearthquakeCP110:1972,BS8110:1983LoadsLoadsGravity loads only(vertically loaded)Dead load:3kN/mLive load:1.5kN/mThespecimen-designMaterialsMaterialsConcrete C20/25 Unit weight 25kN/m E=30G
16、PaReinforcement steel fyk:400MPa existingstructure fyk:450MPa RC infilldowelsDIANA FEA WebinarThespecimendesigndetailsColumnsColumns reinforcementreinforcement 4Y20 longitudinal Spliced right above each slabwith 550mm length Y8/200 stirrupsColumn cross-sectionTransversalTransversal BeamsBeamsreinfor
17、cementreinforcement 2Y20 top 5Y20 bottom Y10/150 stirrupsReinforcement detailfor beamsLongitudinal beamcross-sectionTransversal beamcross-sectionReinforcement detailfor columnsLongitudinalLongitudinal BeamsBeamsreinforcementreinforcement 4Y12 top+bottom Y8/200 stirrupsDIANA FEA WebinarThespecimendes
18、igndetailsRCRC InfillsInfills&DowelsDowelsDifferent amounts of reinforcement for the infills With the north one being the stronger of the twoTwo distinct connection detailsWall reinforcement and connection detailsbetween the walls and the bounding frameDIANA FEA WebinarThespecimendesigndetailsDowels
19、 and starter barsDowels,starter bars andweb reinforcementDIANA FEA WebinarShort dowelsDowels and starter barsRCRC InfillsInfills&DowelsDowelsFirstFirst detaildetail StarterStarter barsbars Web bars connected with the surrounding framethrough lap splicing Same diameter starter bars Epoxy grouted into
20、 the frame members ShortShort dowelsdowels Transfer the shear at the interface between thewall and the frame memberThespecimendesigndetailsRCRC InfillsInfills&DowelsDowelsSecondSecond detaildetail LongerLonger dowelsdowels Act both as dowels and asstarter bars of the webreinforcement These dowels ar
21、e consideredas lap-spliced The clear distance between thedowel and the nearest web bar,violated the maximum cleardistance of 50mm or 4between lapped bars(Specifiedin Eurocode 2(CEN,2004)DowelsDowels and webreinforcementDIANA FEA WebinarDowelsThespecimendesigndetailsDowelsDowels firstfirst detaildeta
22、il waswas usedused toto connectconnect thethe wall:wall:Bottom beam 2nd floor bottom beam Left(west)column of the ground floor Right(east)column of the 1st floorDowelsDowels secondsecond detaildetail waswas usedused toto connectconnect thethe wall:wall:Top beam of the all floors Bottom beam of the 3
23、rd and 4th floors Left(west)of the 2nd,3rd,and 4th floors Right(east)of the 1st,3rd and 4th floorsDIANA FEA WebinarThespecimendesigndetails3-sided CFRP reinforcement jacket to reinforce theedges of the wall at the ground floorThis additional retrofit on the lap length is crucialand constitutes part
24、of the proposed retrofitstrategy to avoid premature tensile lap-splicefailureDIANA FEA WebinarThespecimen-transducers 108 Displacementtransducers 22 Inclinometers 8 Heidenhain linearencoders Elongation/Shortening Rotations Beam supports(Opening/Closing)Beam-middle(Slip)Column(Slip)Shear DeformationD
25、IANA FEA WebinarActuator attachment beamsThespecimen-testsHorizontalHorizontal loadingloadingUni-directional pseudo-dynamic(Ps-D)testing 0.1g acceleration 0.25g accelerationCyclic Displacement history was imposed at the top storey Triangular distribution of forces was imposed 92,-92,89,-125,37,0(mm)
26、Herzeg Novi(Montenegro 1979)accelerogram scaled to 0.25gDIANA FEA WebinarThespecimenGlobalResults0.25g0.25g accelerationacceleration testtest Higher level of damage for the south frame Acrack at the ground floor beam of the foundation at the base of the wall Atensile lap-splice failure appeared in t
27、he outer column at the east side ofthe south frameTensile lap-splicefailure of the columnat the bottomCrack opens at the bottom ofthe column-wallCrack opens at the bottom ofthe column-wallFailure of the lap splicejointS frame N frameHairline cracks develop in thewallDIANA FEA WebinarStorey Displacem
28、ent(mm)Base Shear(kN)ThespecimenGlobalResults0.25g0.25g accelerationacceleration testtestDisplacementDisplacement&ForcesForces1074kN1036kN-1011kN-843kN-600-800-1000-12008006004002000-200-40012001000-125-100-75-50-250255075100125Top Storey Displacement(mm)South WallNorth WallDIANA FEA Webinar-93mm109
29、mm-60-80-100-120806040200-20-40120100024681012141618Time(sec)1st Storey2nd Storey3rd Storey4th StoeryModel in DIANAFEA10.1 releaseAssumptions:Assumptions:Rigid foundationModeling of the south frameCFRPs were not considered2D continuum FEM representation of thesouth frame Rayleigh damping(=0.25%)Ps-D
30、Units:Units:N,m,kgGeometryGeometry definition:definition:same withSERFIN specimen in a 2D model Half of the slab and transversebeams weight was added to thejointsBoundaryBoundary ConstraintsConstraints X,Y Translational-BaseDIANA FEA WebinarDIANAFEAelements&meshConcretePlane stress elementsCQ16MQuad
31、rilateral 8nodesThickness 250mm(5480 elements,size 100*100mm)ReinforcementsteelEmbedded barreinforcement inplane stresselementsCross section-areaof bars(Y8,Y10,Y12,Y20)DowelsBond-slipreinforcement withBeam elements(BAR LINE,INTERF BEAM)Diameter of circle(Y16,Y18,Y20)Interfaces2D line interfaceelemen
32、tsCL12IThickness(width)250mmMassPoint mass elementsPT3TTranslation,pointmass/damping,1nodeHalf weight ofbuilding frames(275 260kg/16points)DIANA FEA WebinarDIANAFEAelements&meshDIANA FEA WebinarDIANAFEAconcretematerialmodelConcreteConcrete Class:Concrete and masonry Material model:Total strain based
33、 crackedmodel(smeared cracking model)Validated parametersLinear material properties Youngs modulus(1.5e10N/m(15GPa),reduced)Poissons ratio(0.2)Mass density(2500kg/m)Total strain based cracked model Rotating crack orientation Crack bandwidth specification(Rots)Tensile behavior Tensile curve(fib Model
34、 Code for Concrete Structures 2010)Tensile strength(2.6e6N/m(2.6MPa)Mode-I tensile fracture energyCompressive behavior Compressive curve(Maekawa cracked concrete curves)Compressive strength(3.3e7N/m(33MPa)Stress confinement(No increase)02.6MP2.6MPa a-0.0025-0.002-0.0015-0.001-0.000500.0005-5-10-15-2
35、0-25-0.014-0.012-0.01-0.008-0.006-0.004-0.0020-5-10-15-20-25-30SYY(MPa)SYY(MPa)Hysteresis for Maekawa model-350Maekawacrackedconcretecurves-0.016EYY-30-33MPa-33MPa5-0.0030.001EYYMaterial model descriptionDIANAFEAresultsDIANA FEA WebinarDIANAFEAReinforcementsmaterialmodelsReinforcementReinforcement s
36、teelsteel Menegotto-Pinto modelLinear elasticity Youngs modulus(2e11N/m(200GPa)Menegotto-Pinto Yield stress(4.5e8N/m(450MPa)for walls,4e8N/m(400MPa)for frame members)ParametersDowelsDowels Von Mises plasticity modelReinforcement bar Youngs modulus(2e11N/m(200GPa)Mass density(7800kg/m)Plasticity mode
37、l(von Mises plasticity)Von Mises parameters Hardening function(no hardening)Yield stress(4.5e8N/m(450MPa)Bond-slip interface Normal stiffness modulus Shear stiffness modulus Bond-slip interface failure model(Shima bondslip function)Compression strength(3.3e7N/m(33MPa)Diameter per barDIANA FEA Webina
38、r600550M550MPaPa4002000-0.015-0.01-0.00500.0050.010.015-200550M550MPaPa-400-600Sxx(MPa)Menegotto-PintomodelMaterial model description-800800-0.020.02ExxHysteresis for Menegotto-Pinto modelDIANAFEAresultsDIANA FEA WebinarDIANAFEA Interface material modelInterfaceInterface 2D2D lineline interfaceinter
39、face typetype Coulomb friction with Brittle Gapping modelLinear material properties Normal stiffness modulus-y Shear stiffness modulus-xCoulomb friction Cohesion(1e15N/m)Friction angle(0.5 rad)Dilatancy angle(0 rad)Interface opening model Gapping model Tensile strength(1e-6N/m)Mode-II shear(Brittle)
40、DIANA FEA WebinarDowelsmodelinDIANAFEABending moment diagram for a dowel bar(left)and shear force diagramfor a dowel(right)according to Keeton&Bishop(1957)Bending moment diagram from DIANAFEAtest for Bond-SlipReinforcement with Beam ElementsDIANA FEA WebinarDowel action according to Pauley et al.(19
41、74)Shear force diagram for DIANAFEAtest for Bond-SlipReinforcement with Beam ElementsDIANAFEAloadsBase excitation with earthquake time history function(0.25g)Gravity vertically loadsDIANA FEA WebinarDIANAFEAanalysisStructural nonlinearNonlinear effectsPhysicallynonlinearTransienteffectsExecutivestep
42、s-timesteps0.005(3000)0.002(7500)Equilibriumiteration IterativemethodSecant(Quasi-Newton)LinesearchConvergence normForce(0.01)(0.005)Displacement(0.01)(0.005)Energy(0.0001)DIANA FEA WebinarEmbedded reinforcement barsRC Infills(monolithic)Model 1DIANAFEAmodel11 1st st casecase modelmodel Dowels model
43、ed as embedded reinforcement bars(cant take shear forces or moments)No interface line elements between the bounding frame and the infill wall(monolithic)DIANA FEA Webinar2D line interface elementsDowel special elementsDIANAFEAmodel22 2ndnd casecase modelmodel Dowels modeled as circular beam bondslip
44、 reinforcement(can take shear forces and moments)With interface line elements between the bounding frame and the infill wall(with gap criterion and Coulomb friction model)Model 2DIANA FEA WebinarDTXDTX(mm)(mm)BaseBase ShearShear(N)(N)BaseBase ShearShear(N)(N)DIANAFEAglobalresultsComparison-91mm-91mm
45、-93mm-93mm109mm109mm108mm108mm-100-1500-5015010050024681012141618Time(sec)Time(sec)DIANAFEADIANAFEA(blue)(blue)VsVs ExperimentExperiment(red)(red)-843kN-843kN-896kN-896kN-5.00E+05-1.00E+061.50E+061.00E+065.00E+050.00E+00024681012141618Time(sec)Time(sec)5.00E+051.50E+061.00E+06-150-1000.00E+00-50-5.0
46、0E+05050100150DIANAFEADIANAFEA(blue)(blue)VsVs ExperimentExperiment(red)(red)4th floor displacementsDIANAFEADIANAFEA(blue)(blue)VsVs ExperimentExperiment(red)(red)1036kN1036kN1034kN1034kN-1.00E+06TopTop StoreyStorey DisplacementDisplacement(mm)(mm)Stiffness degradationModelModel 1 1Base shear forceD
47、IANA FEA WebinarBase Shear(N)DTX(mm)BaseBase ShearShear(N)(N)floor displacementsDIANAFEAglobalresultsComparisonModelModel 2 24thStiffness degradationBase shear force109mm91mm-150-50-1001501005000123456 7-80mm-93mm8910111213141516Time(sec)DIANAFEA(blue)DIANAFEA(blue)VsVs ExperimentExperiment(red)(red
48、)-843kN-843kN-873kN-873kN-5.00E+05-1.00E+061.50E+061.00E+065.00E+050.00E+0002468101214161820TimeTime(sec)(sec)DIANAFEADIANAFEA(blue)(blue)-ExperimentExperiment(red)(red)1127kN1127kN1036kN1036kN1.50E+061.00E+065.00E+05-150-1000.00E+00-50-5.00E+05050100150-1.00E+06Top Storey Displacement(mm)DIANA(blue
49、)DIANA(blue)VsVs ExperimentExperiment(red)(red)DIANA FEA WebinarModelModel 2 2DIANAFEAglobalresultsDIANAFEAlocalresultsDowel cross the interfaceModelModel 2 2Gap criterion at the interfaceDIANA FEA WebinarInterface contribution in the modelDowel action Shear forces4th floor of the modelDIANAFEAlocal
50、resultsModelModel 2 2Cracks-Tensile strength-2.6MPaCrushing-Compressive strength-33MPaDIANA FEA WebinarDIANAFEAlocalresultsModelModel 2 2Reinforcement SYY distributionDIANA FEA WebinarFrame reinforcements yield stress-4e8N/mWeb and dowels reinforcements yield stress 4.5e8N/mDIANAFEAlocalresultsDIANA
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