1. July 21-23, 2006 NEES Annual Meeting 1 NEESR-SG Seismic Performance Assessment and Retrofit of Non-Ductile RC Frames with Infill Walls P. Benson Shing, Jose Restrepo, and Andreas Stavridis University of California, San Diego Kaspar Willam, Sivaselvan Mettupalayam, and Ben Blackard University of Colorado, Boulder Sarah Billington and Marios Kyriakides Stanford University George E. Brown, Jr. Network for Earthquake Engineering Simulation

2. July 21-23, 2006NEES Annual Meeting2 2000 Kocaeli, Turkey Earthquake (EERI) Performance Issues Non-uniform infill – Non-uniform infill – open bottom story open bottom story Asymmetric stiffening Asymmetric stiffening introducing torsion introducing torsion

3. July 21-23, 2006NEES Annual Meeting3 Beneficial Influence of Infill Negro et al. (1996) Bare Frame Infilled Frame

4. July 21-23, 2006NEES Annual Meeting4 Main Issue Brittle shear failure of columns Brittle shear failure of columns Strength degradation of infill and columns leading to soft story mechanism Strength degradation of infill and columns leading to soft story mechanism Soft Story

5. July 21-23, 2006NEES Annual Meeting5 Questions to be Answered What is the threshold ground motion level beyond which an infilled frame will have undesirable performance? What is the threshold ground motion level beyond which an infilled frame will have undesirable performance? How can we raise this threshold with cost- effective strengthening? How can we raise this threshold with cost- effective strengthening?

6. July 21-23, 2006NEES Annual Meeting6 State of the Practice Lack of reliable analysis tools for sound engineering decisions Lack of reliable analysis tools for sound engineering decisions Contribution of infill walls to seismic resistance difficult to assess Contribution of infill walls to seismic resistance difficult to assess Lack of proven cost-effective strengthening methods for infill walls Lack of proven cost-effective strengthening methods for infill walls

7. July 21-23, 2006NEES Annual Meeting7 Complicated Failure Mechanisms

8. July 21-23, 2006NEES Annual Meeting8 Frame-Panel Interaction Weak Infill Strong Infill Frames Tested by Mehrabi et al. (1994)

9. July 21-23, 2006NEES Annual Meeting9 Project Deliverables Improved analysis methods for performance assessment Improved analysis methods for performance assessment Rational assessment procedure considering contribution of infill walls Rational assessment procedure considering contribution of infill walls Validated cost-effective strengthening methods to enhance system-level performance Validated cost-effective strengthening methods to enhance system-level performance

10. July 21-23, 2006NEES Annual Meeting10 Research 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

11. July 21-23, 2006NEES Annual Meeting11 Rational Assessment Procedure 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 Done No Yes NoYes Performance Assessment

12. July 21-23, 2006NEES Annual Meeting12 Retrofit Methods Engineered Cementitious Composites (ECC) for infill strengthening Engineered Cementitious Composites (ECC) for infill strengthening FRP overlay or spray FRP overlay or spray Infill wall-to-beam connection Infill wall-to-beam connection Column strengthening Column strengthening

13. July 21-23, 2006NEES Annual Meeting13 ECC Overlay (Stanford U.) A A A-A ECC Shear connector

14. July 21-23, 2006NEES Annual Meeting14 Small-Scale Tests at Stanford Prism Tests Flexural Tests In-plane Wall Tests

15. July 21-23, 2006NEES Annual Meeting15 2/3-Scale Single-Story Frame Tests (Colorado NEES Site)

16. July 21-23, 2006NEES Annual Meeting16 Tentative Test Matrix for Single- Story Specimens SpecimenInfill Wall Openings Column Retrofit Wall Retrofit 1YNNN 2YNNECC/Connectors 3YYNN 4YYNECC 5YYNFRP or Spray FRP 6YNYHPFRCC, FRP or Spray FRP

17. July 21-23, 2006NEES Annual Meeting17 Full-Scale Shake Table Tests (UCSD NEES Site) Frame with solid infill. Frame with solid infill and retrofit. Frame with infill openings and retrofit.

18. July 21-23, 2006NEES Annual Meeting18 Analysis Methods Advanced computational models for detailed analysis (CU-Boulder) Advanced computational models for detailed analysis (CU-Boulder) Limit analysis methods accounting for multiple failure scenarios Limit analysis methods accounting for multiple failure scenarios Simplified strut models for time histories analysis Simplified strut models for time histories analysis

19. July 21-23, 2006NEES Annual Meeting19 Evaluation of Existing Models Tests by Mehrabi et al. (1994)

20. July 21-23, 2006NEES Annual Meeting20 Comparison of Programs FEAP DIANA Stanford: DIANA Colorado: ABAQUS UCSD: FEAP Principal Tensile Strain Crack and Crushing

21. July 21-23, 2006NEES Annual Meeting21 Infill Joint Modeling with FEAP Element Shear Axial Compression Failure Surface

22. July 21-23, 2006NEES Annual Meeting22 Infilled Frame Analysis (FEAP)

23. July 21-23, 2006NEES Annual Meeting23 Additional Modeling Work Parametric studies to examine influence of model parameters Parametric studies to examine influence of model parameters Calibration of simplified analytical models Calibration of simplified analytical models Predictive analysis and assessment with new experimental results Predictive analysis and assessment with new experimental results Model improvement Model improvement

24. July 21-23, 2006NEES Annual Meeting24 Project Team Benson Shing Jose Restrepo Andreas Stavridis Kaspar Willam Sivaselvan Mettupalayam Ben Blackard Sarah Billington Marios Kyriakides Rutherford & Chekene Joe Maffei Bill Holmes Bret Lizundia

25. July 21-23, 2006NEES Annual Meeting25 Professional Advisory Panel Joe Maffei, R&C (Chair) Joe Maffei, R&C (Chair) Dave Brieholz, BQE Dave Brieholz, BQE John Kariotis, K&A John Kariotis, K&A Ron Mayes, SGH Ron Mayes, SGH Paul Murray, PSDG Paul Murray, PSDG Mike Valley, MKA Mike Valley, MKA Greg Kingsley, KLA Greg Kingsley, KLA Ron Hamburger, SGH

26. July 21-23, 2006NEES Annual Meeting26 Thank You