july 21-23, 2006 nees annual meeting 1 neesr-sg seismic performance assessment and retrofit of...
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July 21-23, 2006July 21-23, 2006 NEES Annual MeetingNEES Annual Meeting 11
NEESR-SGNEESR-SGSeismic Performance Seismic Performance Assessment and Retrofit of Non-Assessment and Retrofit of Non-Ductile RC Frames with Infill Ductile RC Frames with Infill WallsWalls
P. Benson Shing, Jose Restrepo, and Andreas StavridisUniversity of California, San Diego
Kaspar Willam, Sivaselvan Mettupalayam, and Ben BlackardUniversity of Colorado, Boulder
Sarah Billington and Marios KyriakidesStanford University
George E. Brown, Jr. Network for Earthquake Engineering Simulation
July 21-23, 2006July 21-23, 2006 NEES Annual MeetingNEES Annual Meeting 22
2000 Kocaeli, Turkey Earthquake (EERI)
Performance IssuesPerformance Issues
• Non-uniform infill –Non-uniform infill – open bottom storyopen bottom story
• Asymmetric Asymmetric stiffeningstiffening introducing torsionintroducing torsion
July 21-23, 2006July 21-23, 2006 NEES Annual MeetingNEES Annual Meeting 33
Beneficial Influence of InfillBeneficial Influence of InfillNegro et al. (1996)
Bare Frame
Infilled Frame
July 21-23, 2006July 21-23, 2006 NEES Annual MeetingNEES Annual Meeting 44
Main IssueMain Issue
Brittle shear failure of columnsBrittle shear failure of columns Strength degradation of infill Strength degradation of infill
and columns leading to soft and columns leading to soft story mechanismstory mechanism
Soft Story
July 21-23, 2006July 21-23, 2006 NEES Annual MeetingNEES Annual Meeting 55
Questions to be AnsweredQuestions to be Answered
What is the threshold ground motion What is the threshold ground motion level beyond which an infilled frame level beyond which an infilled frame will have undesirable performance?will have undesirable performance?
How can we raise this threshold with How can we raise this threshold with cost-effective strengthening?cost-effective strengthening?
July 21-23, 2006July 21-23, 2006 NEES Annual MeetingNEES Annual Meeting 66
State of the PracticeState of the Practice
Lack of reliable analysis tools for Lack of reliable analysis tools for sound engineering decisions sound engineering decisions
Contribution of infill walls to seismic Contribution of infill walls to seismic resistance difficult to assessresistance difficult to assess
Lack of proven cost-effective Lack of proven cost-effective strengthening methods for infill wallsstrengthening methods for infill walls
July 21-23, 2006July 21-23, 2006 NEES Annual MeetingNEES Annual Meeting 77
Complicated Failure Complicated Failure MechanismsMechanisms
July 21-23, 2006July 21-23, 2006 NEES Annual MeetingNEES Annual Meeting 88
Frame-Panel InteractionFrame-Panel Interaction
Weak Infill
Strong Infill
Frames Tested byMehrabi et al. (1994)
July 21-23, 2006July 21-23, 2006 NEES Annual MeetingNEES Annual Meeting 99
Project DeliverablesProject Deliverables
Improved analysis methods for Improved analysis methods for performance assessmentperformance assessment
Rational assessment procedure Rational assessment procedure considering contribution of infill wallsconsidering contribution of infill walls
Validated cost-effective Validated cost-effective strengthening methods to enhance strengthening methods to enhance system-level performancesystem-level performance
July 21-23, 2006July 21-23, 2006 NEES Annual MeetingNEES Annual Meeting 1010
Research ApproachResearch Approach
Assessment of Existing Modeling Methods
Improved Analysis Methods
Small-Scale Tests on Strengthening Methods
Medium-Scale Tests on Single-Story Frames
Large-Scale Tests on Multi-Story Frames
Component Performance System Performance
Retrofit Methods
July 21-23, 2006July 21-23, 2006 NEES Annual MeetingNEES Annual Meeting 1111
Rational Assessment Rational Assessment ProcedureProcedure
Does the building need strengthening considering the
contribution of infill walls?
Can it be economically and adequately strengthened without additional load resisting systems?
Addition of new loading resisting systems
Infill and/or column strengthening
DoneNo
Yes
NoYesPe
rfo
rman
ce A
sse
ssm
en
t
July 21-23, 2006July 21-23, 2006 NEES Annual MeetingNEES Annual Meeting 1212
Retrofit MethodsRetrofit Methods
Engineered Cementitious Engineered Cementitious Composites (ECC) for infill Composites (ECC) for infill strengtheningstrengthening
FRP overlay or sprayFRP overlay or spray
Infill wall-to-beam connectionInfill wall-to-beam connection
Column strengtheningColumn strengthening
July 21-23, 2006July 21-23, 2006 NEES Annual MeetingNEES Annual Meeting 1313
ECC Overlay (Stanford U.)ECC Overlay (Stanford U.)
A
A A-A
ECC
Shear connector
July 21-23, 2006July 21-23, 2006 NEES Annual MeetingNEES Annual Meeting 1414
Small-Scale Tests at Small-Scale Tests at StanfordStanford
Prism Tests
Flexural Tests
In-plane Wall Tests
July 21-23, 2006July 21-23, 2006 NEES Annual MeetingNEES Annual Meeting 1515
2/3-Scale Single-Story Frame 2/3-Scale Single-Story Frame TestsTests(Colorado NEES Site)(Colorado NEES Site)
July 21-23, 2006July 21-23, 2006 NEES Annual MeetingNEES Annual Meeting 1616
Tentative Test Matrix for Tentative Test Matrix for Single-Story SpecimensSingle-Story Specimens
Specimen InfillWall
WallOpenings
ColumnRetrofit
Wall Retrofit
1 Y N N N
2 Y N N ECC/Connectors
3 Y Y N N
4 Y Y N ECC
5 Y Y N FRP or Spray FRP
6 Y N Y HPFRCC, FRP or Spray FRP
July 21-23, 2006July 21-23, 2006 NEES Annual MeetingNEES Annual Meeting 1717
Full-Scale Shake Table Full-Scale Shake Table TestsTests(UCSD NEES Site)(UCSD NEES Site)
• Frame with solid infill.
• Frame with solid infill and retrofit.
• Frame with infill openings and retrofit.
July 21-23, 2006July 21-23, 2006 NEES Annual MeetingNEES Annual Meeting 1818
Analysis MethodsAnalysis Methods
Advanced computational models for Advanced computational models for detailed analysis (CU-Boulder)detailed analysis (CU-Boulder)
Limit analysis methods accounting for Limit analysis methods accounting for multiple failure scenariosmultiple failure scenarios
Simplified strut models for time Simplified strut models for time histories analysishistories analysis
July 21-23, 2006July 21-23, 2006 NEES Annual MeetingNEES Annual Meeting 1919
Evaluation of Existing Evaluation of Existing ModelsModels
Effect of Infill
0
10
20
30
40
50
60
70
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Displacement, in
Load, ki
ps
Bareframe
Frame w/ Infill
Tests by Mehrabi et al. (1994)
July 21-23, 2006July 21-23, 2006 NEES Annual MeetingNEES Annual Meeting 2020
Comparison of ProgramsComparison of Programs
0 20 40 60 80 100 120
0
20
40
60
80
100
FEAP
DIANA
0
5
10
15
20
25
30
0 0.5 1 1.5 2 2.5 3
Lateral Displacement (in)
Late
ral L
oad
(kip
s)
STANFORDCOLORADOUCSDExperimental
Stanford: DIANAColorado: ABAQUSUCSD: FEAP
PrincipalTensile Strain
Crack and Crushing
July 21-23, 2006July 21-23, 2006 NEES Annual MeetingNEES Annual Meeting 2121
Infill Joint Modeling with Infill Joint Modeling with FEAP ElementFEAP Element
Shear
Axial Compression
Failure Surface
July 21-23, 2006July 21-23, 2006 NEES Annual MeetingNEES Annual Meeting 2222
Infilled Frame Analysis Infilled Frame Analysis (FEAP)(FEAP)
-1.5 -1 -0.5 0 0.5 1 1.5
-60
-40
-20
0
20
40
60
Displacement, in
Forc
e, Kip
s
Single Story Single Bay Concrete Frame with I nfi ll
Finite Element Model
Experiment
July 21-23, 2006July 21-23, 2006 NEES Annual MeetingNEES Annual Meeting 2323
Additional Modeling WorkAdditional Modeling Work
Parametric studies to examine influence Parametric studies to examine influence of model parametersof model parameters
Calibration of simplified analytical modelsCalibration of simplified analytical models
Predictive analysis and assessment with Predictive analysis and assessment with new experimental resultsnew experimental results
Model improvementModel improvement
July 21-23, 2006July 21-23, 2006 NEES Annual MeetingNEES Annual Meeting 2424
Project TeamProject Team
Benson ShingBenson ShingJose RestrepoJose RestrepoAndreas StavridisAndreas Stavridis
Kaspar WillamKaspar WillamSivaselvan MettupalayamSivaselvan MettupalayamBen BlackardBen Blackard
Sarah BillingtonSarah BillingtonMarios Marios
KyriakidesKyriakides
Rutherford & ChekeneRutherford & Chekene
Joe MaffeiJoe MaffeiBill HolmesBill HolmesBret LizundiaBret Lizundia
July 21-23, 2006July 21-23, 2006 NEES Annual MeetingNEES Annual Meeting 2525
Professional Advisory PanelProfessional Advisory Panel
Joe Maffei, R&C (Chair)Joe Maffei, R&C (Chair) Dave Brieholz, BQEDave Brieholz, BQE John Kariotis, K&AJohn Kariotis, K&A Ron Mayes, SGHRon Mayes, SGH Paul Murray, PSDGPaul Murray, PSDG Mike Valley, MKAMike Valley, MKA Greg Kingsley, KLAGreg Kingsley, KLA
Ron Hamburger, SGH
July 21-23, 2006July 21-23, 2006 NEES Annual MeetingNEES Annual Meeting 2626
Thank You