1、Nonlinear FE Analysis of RC Frames Infilled with RC Walls for Seismic Retrofitting in DIANA FEAElpida Georgiou-PhD CandidateSupervisor-Professor Christis Chrysostomou21 November 2017Department of Civil Engineering and GeomaticsCUT is a new state University in Cyprus Growing within the historical cit
2、y 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 StudyThe faculty of Engineering and Technology Department of Electrical Eng.Computer
3、Engineering and Informatics Department of Mechanical Eng.And Materials Science and Engineering Department of Civil Engineering and Geomatics CYPRUS UNIVERSITY OF TECHNOLOGYGeneral dataThe youngest among the leading Young Universities in EuropeCyprus University of Technologybetween 350-400 in the wor
4、ld202 in EuropeIn less than 10 yearsOverviewResearch purposeProcedureExperimental studyGeometry,design,tests,resultsModel in DIANA FEAGeometry definition,elements,mesh,material models,loads,analysisDIANA FEA results comparison with experimental resultsOutcomesFurther workDIANA FEA Webinar Research P
5、urposeStrengthening of existing structures with RC infills within existing frames Limitations in design and construction regardingthis method further investigation is requiredContribution of shear connectors(dowels)Important component of the overall shear resistance capacity of RC Not been yet analy
6、zed adequately Complicated mechanism Not clear how to design them A parametric study is necessarySimulation of a full-scale Ps-D test in DIANA FEA Numerical experiments Global&Local resultsDIANA FEA Webinar Original FrameRetrofitted FrameProcedurePrototype model-SERFIN project-Full-scale case study-
7、Model correctly reflects the real situation-Results&dataDIANA FEA for simulation-FEM of the frame to represent the experiment-Validation with experimental results-Nonlinear hysteretic behavior of materials at the local level-Capture and evaluate the behavior of RC infillsReliable study of any buildi
8、ng parameter-Numerical experiments and parametric studies DIANA FEA Webinar Experimental studySERIESSeismic Engineering Research Infrastructures of European Synergies European Commission,Framework Programme 7SERFIN projectSeismic Retrofitting of RC Frames with RC Infilling First time in the world a
9、full-size test of this type of specimen 18 months(December 2013 July 2015)European Laboratory of Structural Assessment(ELSA)of the Joint Research Centre in Ispra(Italy)Important Experimental results&DataStructural Engineering International Journal of IABSE,23(2),159-166,(2013)-http:/ Scientific and
10、Technical Research Reports,(2013)-https:/ec.europa.eu/jrc/en/publication/eur-scientific-and-technical-research-reports/seismic-retrofitting-rc-frames-rc-infilling-serfin-project-series-transnational-accessParticipants:Cyprus University of Technology CoordinatorUniversity of Nantes(France)University
11、of CyprusDENCO Design&Engineering Consultants(Greece)DIANA FEA Webinar The specimen-geometryRC infilling 2 end exterior frames only Spaced at 6m Linked by a 0.15m thick RC slab and 4 transverse beams 35x65 RC infill wall has the same thickness as the width of the frame members(0.25m)Central bay 2.5m
12、/Two exterior bays 3m(centre to centre)Columns 25x40,Beams 25x50Multi-storey 4-storeys Total specimen height 12m-excluding the foundation Storey height 3mMulti-bay 3-bays Centre-line length of the specimen was 8.5mDIANA FEA Webinar EASTWESTSOUTHWALLThe specimen-designDesign standard Typical building
13、 in the 70s-80s in CyprusNo specific design standardNo provisions for earthquakeCP110:1972,BS8110:1983LoadsGravity loads only(vertically loaded)Dead load:3kN/mLive load:1.5kN/mMaterialsConcrete C20/25 Unit weight 25kN/m E=30GPaReinforcement steel fyk:400MPa existing structure fyk:450MPa RC infill do
14、welsDIANA FEA Webinar The specimen design detailsColumns reinforcement 4Y20 longitudinal Spliced right above each slab with 550mm length Y8/200 stirrupsColumn cross-sectionTransversal Beams reinforcement 2Y20 top 5Y20 bottom Y10/150 stirrupsReinforcement detailfor beamsLongitudinal beamcross-section
15、Transversal beamcross-sectionReinforcement detailfor columnsLongitudinal Beams reinforcement 4Y12 top+bottom Y8/200 stirrupsDIANA FEA Webinar The specimen design detailsRC Infills&DowelsDifferent amounts of reinforcement for the infills With the north one being the stronger of the twoTwo distinct co
16、nnection detailsWall reinforcement and connection details between the walls and the bounding frameDIANA FEA Webinar The specimen design detailsDowels and starter barsDowels,starter bars and web reinforcementDIANA FEA Webinar Short dowelsDowels and starter barsRC Infills&DowelsFirst detail Starter ba
17、rs Web bars connected with the surrounding frame through lap splicing Same diameter starter bars Epoxy grouted into the frame members Short dowels Transfer the shear at the interface between the wall and the frame memberThe specimen design detailsRC Infills&DowelsSecond detail Longer dowels Act both
18、 as dowels and as starter bars of the web reinforcement These dowels are considered as lap-spliced The clear distance between the dowel and the nearest web bar,violated the maximum clear distance of 50mm or 4between lapped bars(Specified in Eurocode 2(CEN,2004)DowelsDowels and web reinforcementDIANA
19、 FEA Webinar DowelsThe specimen design detailsDowels first detail was used to connect the wall:Bottom beam 2ndfloor bottom beam Left(west)column of the ground floor Right(east)column of the 1stfloorDowels second detail was used to connect the wall:Top beam of the all floors Bottom beam of the 3rdand
20、 4thfloors Left(west)of the 2nd,3rd,and 4thfloors Right(east)of the 1st,3rdand 4thfloorsDIANA FEA Webinar The specimen design details3-sided CFRP reinforcement jacket to reinforce the edges of the wall at the ground floorThis additional retrofit on the lap length is crucial and constitutes part of t
21、he proposed retrofit strategy to avoid premature tensile lap-splice failureDIANA FEA Webinar The specimen-transducers 108 Displacement transducers 22 Inclinometers 8 Heidenhain linear encoders Elongation/Shortening Rotations Beam supports(Opening/Closing)Beam-middle(Slip)Column(Slip)Shear Deformatio
22、nDIANA FEA Webinar The specimen-testsHorizontal loadingUni-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)Actuator attachment beamsHerzeg Novi(M
23、ontenegro 1979)accelerogram scaled to 0.25gDIANA FEA Webinar The specimen Global Results0.25g acceleration test Higher level of damage for the south frame A crack at the ground floor beam of the foundation at the base of the wall A tensile lap-splice failure appeared in the outer column at the east
24、side of the south frameCrack opens at the bottom of the column-wallTensile lap-splice failure of the column at the bottomCrack opens at the bottom of the column-wallFailure of the lap splice jointS frame N frameHairline cracks develop in the wallDIANA FEA Webinar The specimen Global Results0.25g acc
25、eleration testDisplacement&Forces1074kN1036kN-1011kN-843kN-1200-1000-800-600-400-200020040060080010001200-125-100-75-50-250255075100125Base Shear(kN)Top Storey Displacement(mm)South WallNorth WallDIANA FEA Webinar-93mm109mm-120-100-80-60-40-20020406080100120024681012141618Storey Displacement(mm)Time
26、(sec)1st Storey2nd Storey3rd Storey4th StoeryModel in DIANA FEA 10.1 releaseAssumptions:Rigid foundation Modeling of the south frame CFRPs were not considered 2D continuum FEM representation of the south frame Rayleigh damping(=0.25%)Ps-DUnits:N,m,kgGeometry definition:same with SERFIN specimen in a
27、 2D model Half of the slab and transverse beams weight was added to the jointsBoundary Constraints X,Y Translational-BaseDIANA FEA Webinar DIANA FEA elements&meshConcretePlane stress elementsCQ16MQuadrilateral 8nodesThickness 250mm(5480 elements,size 100*100mm)Reinforcement steelEmbedded bar reinfor
28、cement in plane stress elementsCross section-area of bars(Y8,Y10,Y12,Y20)DowelsBond-slip reinforcement with Beam elements(BAR LINE,INTERF BEAM)Diameter of circle(Y16,Y18,Y20)Interfaces2D line interface elementsCL12IThickness(width)250mmMassPoint mass elementsPT3TTranslation,point mass/damping,1nodeH
29、alf weight of building frames(275 260kg/16points)DIANA FEA Webinar DIANA FEA elements&meshDIANA FEA Webinar DIANA FEA concrete material modelConcrete Class:Concrete and masonry Material model:Total strain based cracked model(smeared cracking model)Validated parameters Youngs modulus(1.5e10N/m(15GPa)
30、,reduced)Poissons ratio(0.2)Mass density(2500kg/m)Linear material properties Rotating crack orientation Crack bandwidth specification(Rots)Total strain based cracked model Tensile curve(fib Model Code for Concrete Structures 2010)Tensile strength(2.6e6N/m(2.6MPa)Mode-I tensile fracture energyTensile
31、 behavior Compressive curve(Maekawa cracked concrete curves)Compressive strength(3.3e7N/m(33MPa)Stress confinement(No increase)Compressive behaviorMaekawa cracked concrete curvesHysteresis for Maekawa model-33MPa-35-30-25-20-15-10-50-0.016-0.014-0.012-0.01-0.008-0.006-0.004-0.0020SYY(MPa)EYY2.6MPa-3
32、0-25-20-15-10-505-0.003-0.0025-0.002-0.0015-0.001-0.000500.00050.001SYY(MPa)EYYMaterial model descriptionDIANA FEA resultsDIANA FEA Webinar DIANA FEA Reinforcements material modelsReinforcement steel Menegotto-Pinto modelDowels Von Mises plasticity model Youngs modulus(2e11N/m(200GPa)Linear elastici
33、ty Yield stress(4.5e8N/m(450MPa)for walls,4e8N/m(400MPa)for frame members)ParametersMenegotto-Pinto Youngs modulus(2e11N/m(200GPa)Mass density(7800kg/m)Plasticity model(von Mises plasticity)Reinforcement bar Hardening function(no hardening)Yield stress(4.5e8N/m(450MPa)Von Mises parameters Normal sti
34、ffness modulus Shear stiffness modulus Bond-slip interface failure model(Shima bondslip function)Compression strength(3.3e7N/m(33MPa)Diameter per barBond-slip interfaceDIANA FEA Webinar Menegotto-Pinto modelMaterial model description550MPa550MPa-800-600-400-2000200400600800-0.02-0.015-0.01-0.00500.0
35、050.010.0150.02Sxx(MPa)ExxHysteresis for Menegotto-Pinto modelDIANA FEA resultsDIANA FEA Webinar DIANA FEA Interface material modelInterface 2D line interface type Coulomb friction with Brittle Gapping model Normal stiffness modulus-y Shear stiffness modulus-xLinear material properties Cohesion(1e15
36、N/m)Friction angle(0.5 rad)Dilatancy angle(0 rad)Coulomb friction Gapping model Tensile strength(1e-6N/m)Mode-II shear(Brittle)Interface opening modelDIANA FEA Webinar Dowels model in DIANA FEABending moment diagram for a dowel bar(left)and shear force diagram for a dowel(right)according to Keeton&B
37、ishop(1957)Bending moment diagram from DIANA FEA test for Bond-Slip Reinforcement with Beam ElementsDIANA FEA Webinar Dowel action according to Pauley et al.(1974)Shear force diagram for DIANA FEA test for Bond-Slip Reinforcement with Beam ElementsDIANA FEA loadsBase excitation with earthquake time
38、history function(0.25g)Gravity vertically loadsDIANA FEA Webinar DIANA FEA analysisStructural nonlinearNonlinear effectsPhysically nonlinearTransient effectsExecutive steps-time steps0.005(3000)0.002(7500)Equilibrium iteration Iterative methodSecant(Quasi-Newton)Line searchConvergence normForce(0.01
39、)(0.005)Displacement(0.01)(0.005)Energy(0.0001)DIANA FEA Webinar DIANA FEA model 1Embedded reinforcement barsRC Infills(monolithic)Model 11stcase model Dowels modeled as embedded reinforcement bars(cant take shear forces or moments)No interface line elements between the bounding frame and the infill
40、 wall(monolithic)DIANA FEA Webinar DIANA FEA model 22D line interface elementsDowel special elements2ndcase model Dowels modeled as circular beam bondslip reinforcement(can take shear forces and moments)With interface line elements between the bounding frame and the infill wall(with gap criterion an
41、d Coulomb friction model)Model 2DIANA FEA Webinar DIANA FEA global results Comparison-93mm-91mm109mm108mm-150-100-50050100150024681012141618DTX(mm)Time(sec)DIANA FEA(blue)Vs Experiment(red)-896kN-843kN1036kN1034kN-1.00E+06-5.00E+050.00E+005.00E+051.00E+061.50E+06024681012141618Base Shear(N)Time(sec)
42、DIANA FEA(blue)Vs Experiment(red)-1.00E+06-5.00E+050.00E+005.00E+051.00E+061.50E+06-150-100-50050100150Base Shear(N)Top Storey Displacement(mm)DIANA FEA(blue)Vs Experiment(red)4thfloor displacementsStiffness degradationModel 1Base shear forceDIANA FEA Webinar DIANA FEA global results ComparisonModel
43、 24thfloor displacementsStiffness degradationBase shear force-93mm-80mm109mm91mm-150-100-50050100150012345678910111213141516DTX(mm)Time(sec)DIANA FEA(blue)Vs Experiment(red)-843kN-873kN1127kN1036kN-1.00E+06-5.00E+050.00E+005.00E+051.00E+061.50E+0602468101214161820Base Shear(N)Time(sec)DIANA FEA(blue
44、)-Experiment(red)-1.00E+06-5.00E+050.00E+005.00E+051.00E+061.50E+06-150-100-50050100150Base Shear(N)Top Storey Displacement(mm)DIANA(blue)Vs Experiment(red)DIANA FEA Webinar Model 2DIANA FEA global resultsDIANA FEA local resultsDowel cross the interfaceModel 2Gap criterion at the interfaceDIANA FEA
45、Webinar Interface contribution in the modelDowel action Shear forces4th floor of the modelDIANA FEA local resultsModel 2Cracks-Tensile strength-2.6MPaCrushing-Compressive strength-33MPaDIANA FEA Webinar DIANA FEA local resultsModel 2Reinforcement SYY distribution DIANA FEA Webinar Frame reinforcemen
46、ts yield stress-4e8N/mWeb and dowels reinforcements yield stress 4.5e8N/mDIANA FEA local resultsDIANA FEA Webinar Model 2Reinforcement SXX distribution Frame reinforcements yield stress-4e8N/mWeb and dowels reinforcements yield stress 4.5e8N/mDIANA FEA Vs Experiment resultsDIANA FEA Webinar Failure
47、of the column at the bottomCrack opens at the bottom of the column-wall-0.4-0.200.20.40123456789101112131415Acceleration(m/s)Time(sec)DIANA FEA Vs Experiment resultsHairline cracks developed in the wallDIANA FEA Webinar-0.4-0.200.20.40123456789101112131415Acceleration(m/s)Time(sec)OutcomesDIANA FEA
48、Webinar Good agreement between real case study and DIANA resultsType of elements,Mesh,Material models capacity,Nonlinear time history analysis,Iteration methods,Convergence criteriaThe transient analysis took 7 hours for Model 2(0.002-time step)for 7500 stepsWe have calibrated model which can be use
49、d for parametric studiesFuture workDIANA FEA Webinar The calibrated model of RC infills will be used toStudy configurations with reduced number of dowels to complement the experimental resultsStudy the interaction between RC infills and bounding frame both in the local and global levelThank you for your attention!es.georgiouedu.cut.ac.cy
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