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Seismic Design Methodology for Precast Concrete Floor Diaphragms

Seismic Design Methodology for Precast Concrete Floor Diaphragms. Research to Practice Webinar April 23, 2012. Dr. Ned M. Cleland, P.E Dr. Robert B. Fleischman Dr. S.K. Ghosh, P.E. Blue Ridge Design, Inc University of Arizona SKG Associates.

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Seismic Design Methodology for Precast Concrete Floor Diaphragms

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  1. Seismic Design Methodology for Precast Concrete Floor Diaphragms Research to Practice Webinar April 23, 2012 Dr. Ned M. Cleland, P.E Dr. Robert B. Fleischman Dr. S.K. Ghosh, P.E. Blue Ridge Design, Inc University of Arizona SKG Associates Sponsored by the Earthquake Engineering Research Institute (EERI) and the Network for Earthquake Engineering Simulation (NEES)

  2. Outline NEES/EERI Webinar April 23 2012 Introduce PCI/NSF/CPF DSDM Research Effort Review Key Behaviors of Precast Diaphragms and Design Philosophy Adopted Summarize DSDM Research Project Findings Present Precast Diaphragm Design Procedure Cover Precast Diaphragm Design Example Discuss Codification Efforts

  3. Outline NEES/EERI Webinar April 23 2012 Introduce PCI/NSF/CPF DSDM Research Effort Review Key Behaviors of Precast Diaphragms and Design Philosophy Adopted Summarize DSDM Research Project Findings Present Precast Diaphragm Design Procedure Cover Precast Diaphragm Design Example Discuss Codification Efforts

  4. Diaphragm Action Diaphragm action is intended to carry seismic forces horizontally in the floor slab to walls and frames… NEES/EERI Webinar April 23 2012

  5. Precast Diaphragm Details Precast floors can be vulnerable due to the need to transfer forces at discrete locations across floor joints between precast panels NEES/EERI Webinar April 23 2012

  6. Precast Diaphragm Past Performance NEES/EERI Webinar April 23 2012

  7. DSDM Project Project Co-funders: CPF, PCI and NSF Objective: Develop an industry endorsed seismic design methodology for precast concrete diaphragms. Scope: Untopped and topped composite precast floor diaphragms. NEES/EERI Webinar April 23 2012

  8. University of Arizona Robert Fleischman Consortium Leader University of California Lehigh University Industry Liaison San Diego Clay Naito, PI S. K. Ghosh, Co-PI DSDM Task Group Jose’ Restrepo, PI Richard Sause, Co-PI Producer Members Producer Members Industry Advisory Panel DSDM Consortium NEES/EERI Webinar April 23 2012

  9. DSDM Task Group Graduate Researchers Dichuan Zhang, Ge Wan, Michael Mielke, Alicia Mullenbach, Univ. of Arizona Liling Cao, Rui Ren, Wesley Peter, Lehigh Univ. Matt Schoettler and Andrea Belleri, UCSD Industry Task Group S.K.Ghosh DSDM Task Group Chair President, S. K. Ghosh Associates R. Becker Vice President Spancrete Industries, Inc. N. Cleland President Blue Ridge Design, Inc. Tom D’Arcy President Consulting Engineers Group N. Hawkins Professor Emeritus Univ. of Illinois Doug Sutton Professor Purdue University Harry Gleich Vice President Metromont Prestress Paul Johal Research Director PCI Joe Maffei Engineering Consultant Rutherford & Chekene Engineers Susie Nakaki President The Nakaki Bashaw Group, Inc. Dave Dieter Vice-President MidState Precasters Chuck Magnesio Vice-President JVI, Inc NEES/EERI Webinar April 23 2012

  10. Outline NEES/EERI Webinar April 23 2012 Introduce PCI/NSF/CPF DSDM Research Effort Review Key Behaviors of Precast Diaphragms and Design Philosophy Adopted Summarize DSDM Research Project Findings Present Precast Diaphragm Design Procedure Cover Precast Diaphragm Design Example Discuss Codification Efforts

  11. Diaphragm Forces An aspect of diaphragm behavior not elucidated in the codes is the relationship of the design forces used in equivalent lateral force (ELF) procedures to the inertial forces that may actually develop in floors during a seismic event. Fleischman and Farrow, Eq. Eng & Struc. Dyn, 2001 Diaphragm peak inertial forces may significantly exceed current design values NEES/EERI Webinar April 23 2012

  12. Current Design Code The presence of large inertial forces can be critical in precast floor systems: • In combination with complex load paths in floor systems, can lead to inelastic diaphragm action. • Inelastic deformation demands in precast diaphragms will tend to concentrate in the joints between precast units, and only at certain joints. • These demands can exceed the deformation capacity of reinforcing details developed without this consideration, leading to a nonductile diaphragm failure. • High diaphragm flexibility due to the inherently less stiff jointed system, in long floor spans where precast is used effectively, could lead to excessive drift of gravity system columns NEES/EERI Webinar April 23 2012

  13. Elastic Design Option (EDO) YeFpx Maximum Force Demand Amplified design force Fpx Current design force Diaphragm Design Approach Diaphragm force (MCE) Possible Nonductile Response Diaphragm lateral displacement NEES/EERI Webinar April 23 2012

  14. Shear Failure WvYDFpx DBE force demand Chord Failure YDFpx Capacity Design Amplified design force Fpx Current design MCE ductility demand DSDM Design Philosophy Basic Design Option (BDO) Diaphragm force Elastic design option force Diaphragm lateral displacement NEES/EERI Webinar April 23 2012

  15. Within allowable deformation limits in MCE YrFpx Yields in DBE Fpx Current design force DSDM Design Philosophy Reduced Design Option (RDO) Diaphragm force Elastic design option Diaphragm lateral displacement NEES/EERI Webinar April 23 2012

  16. Fpx Current design force MDE LDE HDE Connector Classification DSDM Design Philosophy Diaphragm force EDO BDO RDO Diaphragm lateral displacement NEES/EERI Webinar April 23 2012

  17. Outline NEES/EERI Webinar April 23 2012 Introduce PCI/NSF/CPF DSDM Research Effort Review Key Behaviors of Precast Diaphragms and Design Philosophy Adopted Summarize DSDM Research Project Findings Present Precast Diaphragm Design Procedure Cover Precast Diaphragm Design Example Discuss Codification Efforts

  18. DSDM Research Flow • Diaphragm seismic force • Diaphragm flexibility limits MDOF Dynamic Analysis Scaled Shake Table Test • Capacity Design Factors. • Internal Force Paths Structure Level (UCSD)  Diaphragm Level (UA) FE Pushover Analysis 3D FE Dynamic Analysis Detail Level (LU) • Characteristics of diaphragm details • Connection classification Full-Scale Detail Tests Hybrid Testing of Joints NEES/EERI Webinar April 23 2012

  19. Precast Diaphragm Connector Testing Connection Details Evaluation Experimental Classify connectors: • Low Defo (LDE) • Mod Defo (MDE) • High Defo (HDE) Previous Test Results Evaluation Analytical NEES/EERI Webinar April 23 2012

  20. Modeling of Chord Connector a=0.7 NEES/EERI Webinar April 23 2012

  21. Cyclic response Modeling of JVI Connector NEES/EERI Webinar April 23 2012

  22. Modeling of Ductile Mesh NEES/EERI Webinar April 23 2012

  23. Nonlinear coupled springs and contact elements Diaphragm Analytical Modelling Discrete FE models NEES/EERI Webinar April 23 2012

  24. Prototype Structure #1: Parking Garage Model NEES/EERI Webinar April 23 2012

  25. PDH Test NEES/EERI Webinar April 23 2012

  26. PDH Test Results: Flexure q M M Minor Cracking CH MCE CH Service CH DBE Major Cracking/Crushing Weld Fracture Joint Flexural Response CH Bi-dir DBE BK MCE NEES/EERI Webinar April 23 2012

  27. Shaking Table Structure NEES/EERI Webinar April 23 2012

  28. δ Test Comparison: Knoxville Knoxville DBE Diaphragm midspan roof drift NEES/EERI Webinar April 23 2012

  29. Phase III: Design Methodology Development NEES/EERI Webinar April 23 2012

  30. Connector Elements Chord connector: Nonlinear springs • Symmetry • boundary Precast units: Plane stress element Moment frame 3D beam element Shear connector: Nonlinear springs Spandrel: 2D beam element Column: 3D beam element Shear wall 3D shell element Modeling of Evaluation Structure NEES/EERI Webinar April 23 2012

  31. Suite of Ground Motions SDC E SDC C NEES/EERI Webinar April 23 2012

  32. Trial Design Factors Diaphragm Force Amplification Factor Y T T, δ Chord connector δ SDC E AR=3 NEES/EERI Webinar April 23 2012

  33. Design Methodology Verification: Prototype Structures 4-Story Parking Structure NEES/EERI Webinar April 23 2012

  34. Design Methodology Verification: Prototype Structures 8-Story Office Building NEES/EERI Webinar April 23 2012

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