Presentation on theme: "Development of Self-Centering Steel Plate Shear Walls (SC-SPSW)"— Presentation transcript:
1 Development of Self-Centering Steel Plate Shear Walls (SC-SPSW) Jeff BermanAssistant ProfessorUniversity of Washington
2 NEESR-SG: Steel Plate Shear Wall Research Jeff Berman and Laura LowesLarry FahnestockMichel BruneauGraduate Students:UW: Patricia Clayton, David Webster UIUC: Dan Borello, Alvaro Quinonez UB: Dan DowdenK.C. TsaiRafael SabelliSponsored by NSF through the George E. Brown NEESR ProgramMaterial Donations from AISC
3 Project Overview a ~43° Resilient SPSW Analysis and Verification of PerformanceSubassemblage TestingShake TableTestingFull-Scale TestingFill Critical Knowledge Gapsa~43°Cyclic Inelastic Tension Field ActionSPSW Damage States and FragilitiesCoupled SPSWTesting (MUST-SIM)
4 US Northridge Earthquake (1994) MotivationCurrent U.S. seismic design codesLife Safety and Collapse PreventionMaximum Considered Earthquake (MCE)U.S. Earthquakes since 19701:Only 2 people per year die due to structural collapse$2 billion per year in economic lossUS Northridge Earthquake (1994)Haiti Earthquake (2010)1 ATC-69 (2008)
5 Resilient SPSWs: Motivation Steel Plate Shear Walls (SPSWs):Thin web plates: tension field actionHigh initial stiffnessDuctileDistributed yieldingReplaceable “fuses” (web plates)However,Damage in HBEs and VBEsnot as easy to repair/replaceHow can we limit damage to HBEs and VBEs to provide a quicker return to occupancy following an earthquake?(Vian and Bruneau 2005)
7 SC-SPSW Research Overview Analytical ResearchPerformance-Based Design ProcedureAnalysis and Verification of PerformanceSystem BehaviorSubassembly Testing(U. of Washington)Experimental ResearchShake Table Testing(U. at Buffalo)Full-scale Testing(NCREE, Taiwan)
8 R-SPSW Mechanics Distributed loads on frame from web plates Compression of HBE from three components:PTWeb plate loads on VBEWeb plate loads on HBE
10 Analytical Model Nonlinear model in OpenSees SPSW modeled using strip method:Tension-only strips with pinched hysteresisStrips oriented in direction of tension field
11 Analytical Model (cont.) PT connection model:Compression-only springs at HBE flangesRocking about HBE flangesShear transferDiagonal springsPT tendonsTruss elements with initial stress (Steel02)HBEVBERigid offsetsPhysical ModelAnalytical ModelCompression-only springs at HBE flangesDiagonal springs to transfer shear
12 Dynamic Analyses3 and 9 story prototypes based on SAC buildings: 4-6 SPSW baysEach model subjected to 60 LA SAC ground motions representing 3 seismic hazard levels50% in 50 year10% in 50 year2% in 50 yearUsed OpenSeesMP to run ground motions in parallel on TeraGrid machinesProcessor = 0Processor = 1RangerR-SPSW modelProcessor = n-1
13 Analytical Summary All performance objectives met !!! Results for typical 9-story SC-SPSWdesigned WITHOUT optional 50% in 50 year “No repair” performance obj.VDV10/50D10/50V2/50D2/50D50/50V50/50VwindPerformance Objectives:No plate repair (Story drift < 0.5%) in 50/50Recentering (Residual Drift < 0.2%) in 10/50Story drift < 2.0% in 10/50 (represents DBE)Limited PT, HBE, and VBE yielding in 2/50No RepairCollapsePreventionRepair of Plates OnlyAll performance objectives met !!!
14 UW Component Tests Reaction Blocks Pin to Allow VBE Rotation Roller to Allow Gap OpeningPin to Allow VBE RotationTarget Deformation of SpecimenLaboratory ConfigurationSubassemblage
15 R-SPSW Testing Connection decompression Development of tension field Flag-shaped hysteresisResidual web plate deformation after test
16 Comparison of Parameters Change in number of PT strandsChange in web plate thicknessKrAffects recompression stiffness, Kr, due to change in PT stiffnessAffects decompression momentAffects system strength and energy dissipationAffects post-decompression stiffness
17 Comparison with Idealized Response 1st Cycle2nd CycleVSC-SPSWDPlate yieldsUnloadingConnectionDecompressionRecompressionPlates UnloadedMore energy dissipation than assumedSome “compressive” resistance due to geometric stiffening
18 Web Plate Behavior Study FE modelingResidual LoadExperimental testingPins~25% of yield strength(Webster 2011)
19 Comparison with Models OpenSees modelWith and without compressive resistance in stripsFuture improvements to strip model:Modify strain hardening rules to account for cyclic yieldingQuantify compression in SPSW strip model
20 Kim and Christopoulos (2008) Frame ExpansionAs PT connection decompresses, VBEs spread apartGarlock (2002)Kim and Christopoulos (2008)Can cause floor damage or increase frame demands if beam growth is restrained, especially at 1st floor beam
21 Accommodation of Frame Expansion Garlock (2007)Flexible collector beams connecting PT frame and composite slabApplies additional point loads along beamDamage to collector beamsKim and Christopoulos (2008)Sliding interface between slab and beamsEliminates slab restraint
22 Elimination of Frame Expansion Rocking about HBE centerline (Pin)NewZ-BREAKSSRocking about top flange only
23 Testing at NEES@Buffalo Quasi-Static tests1/3 scale, 3-storyVarious PT connection detailsFull plate and Strips
24 Comparison of Behavior Flange rocking provides better re-centering because of decompression momentNewZ-BREAKSS prevents floor damage due to frame expansion.
25 UB Shake Table Tests 6 degree-of-freedom shake table Same specimens as quasi-static testsScheduled for completion in fall 2012
26 System-level TestingNational Center for Earthquake Engineering (NCREE) in Taiwan2-story, full scale SC-SPSWSingle actuatorQuasi-static loadingSummer 2012
27 NCREE SpecimensPT column baseColumn can rock about its flanges
28 NCREE Specimens PT column base 2 specimens Column can rock about its flanges2 specimensFlange rocking HBEsNewZ-BREAKSS Connection(Top flange rocking HBEs)
29 Conclusions Performance-based design procedure developed for SC- SPSW: Elastic behavior during frequent eventsWeb plate yielding and recentering during DBE eventsCollapse prevention during MCE eventsAnalytical studies show SC-SPSWs are capable of meeting proposed performance objectivesExperimental subassembly tests show ‘simple’ models are conservative and have room for improvementFuture testing will verify performance on system level
30 Thank YouTo provide insight into my background, here are some projects I’ve worked onQuestions?
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