Seismic Design Methodology for Precast Concrete Floor Diaphragms Research to Practice Webinar April 23, 2012 Sponsored by the Earthquake Engineering Research Institute (EERI) and the Network for Earthquake Engineering Simulation (NEES) 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 Research to Practice Webinar April 23, 2012 Sponsored by the Earthquake Engineering Research.
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Seismic Design Methodology for Precast Concrete Floor
Diaphragms
Research to Practice WebinarApril 23, 2012
Sponsored by the Earthquake Engineering Research Institute (EERI) and the Network for Earthquake Engineering
Simulation (NEES)
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
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:2 of 34
OutlineOutline
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
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:3 of 34
OutlineOutline
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
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:4 of 34
Diaphragm Action
Diaphragm action is intended to carry seismic forces horizontally in the floor slab to walls and frames…
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:5 of 34
Precast floors can be vulnerable due to the need to transfer forces at discrete locations across floor joints between precast panels
Dry Chord Connection
Dry Chord Connection
Web Connection
Slug
Faceplate
Anchorage Bars
Panel-To-Panel Web Connection
Field Topped Pre-Topped
Web Connection
Precast Diaphragm Details
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:6 of 34
Precast Diaphragm Past Performance
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:7 of 34
DSDM Project
Objective: Develop an industry endorsed seismic design methodology for precast concrete diaphragms.
Scope: Untopped and topped composite precast floor diaphragms.
Project Co-funders: CPF, PCI and NSF
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:8 of 34
DSDM Consortium
Producer Members
University of CaliforniaSan Diego
Jose’ Restrepo, PI
Producer Members
Lehigh UniversityClay Naito, PI
Richard Sause, Co-PI
Industry Advisory Panel
Industry LiaisonS. K. Ghosh, Co-PI
University of ArizonaRobert FleischmanConsortium Leader
DSDM Task Group
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:9 of 34
DSDM Task Group
S.K.GhoshDSDM Task Group Chair
President, S. K. Ghosh Associates
R. BeckerVice President
Spancrete Industries, Inc.
N. ClelandPresident
Blue Ridge Design, Inc.
Tom D’ArcyPresident
Consulting Engineers Group
N. HawkinsProfessor Emeritus
Univ. of Illinois
Paul JohalResearch Director
PCI
Joe MaffeiEngineering ConsultantRutherford & Chekene
Engineers
Susie NakakiPresident
The Nakaki Bashaw Group, Inc.
Doug SuttonProfessor
Purdue University
Harry GleichVice President
Metromont Prestress
Dave DieterVice-President
MidState Precasters
Industry Task Group
Chuck MagnesioVice-President
JVI, IncDichuan Zhang, Ge Wan, Michael Mielke, Alicia
Mullenbach, Univ. of Arizona
Liling Cao, Rui Ren, Wesley Peter, Lehigh Univ.
Matt Schoettler and Andrea Belleri, UCSD
Graduate Researchers
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:10 of 34
OutlineOutline
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
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:11 of 34
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.
Diaphragm Forces
Fleischman and Farrow, Eq. Eng & Struc. Dyn, 2001
Diaphragm peak inertial forces may significantly exceed current design values
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:12 of 34
The presence of large inertial forces can be critical in precast floor systems:
Current Design Code
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 2012PCI/NSF/CPFPART 1:13 of 34
eFpx
Elastic Design Option (EDO)
Maximum Force Demand
Diaphragm force
Diaphragm lateral displacement
forceforce
L
d
L
d
VV
MMCurrent design force Fpx
Possible Nonductile Response
(MCE)Amplified
design force
Diaphragm Design Approach
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:14 of 34
DBE force demand
DFpx
Elastic design optionDiaphragm force
Diaphragm lateral displacement
Current designFpx
MCE ductility demand
DSDM Design Philosophy
Basic Design Option (BDO)
Amplified design force
force
Capacity Design
Shear Failure
Chord Failure
vDFpx
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:15 of 34
Elastic design optionDiaphragm force
Diaphragm lateral displacement
Current design force Fpx
rFpx
DSDM Design Philosophy
Reduced Design Option (RDO)
Yields in DBEWithin allowable deformation limits in MCE
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:16 of 34
EDODiaphragm force
Diaphragm lateral displacement
Current design force Fpx
RDO
LDE MDEHDE
Connector Classification
BDO
DSDM Design Philosophy
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:17 of 34
OutlineOutline
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