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
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:18 of 34
DSDM Research Flow
Diaphragm Level (UA)
Capacity Design Factors.
Internal Force Paths
Structure Level (UCSD)
Diaphragm seismic force
Diaphragm flexibility limits
FpxFpxFpx
FE Pushover Analysis 3D FE Dynamic Analysis
MDOF Dynamic Analysis
Detail Level (LU)
Characteristics of diaphragm details
Connection classification
Full-Scale Detail Tests
Scaled Shake Table Test
Hybrid Testing of Joints
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:19 of 34
Precast Diaphragm Connector Testing
Classify connectors:
Low Defo (LDE)
Mod Defo (MDE)
High Defo (HDE)
Connection Details Evaluation
Previous Test Results Evaluation
Experimental
Analytical
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:20 of 34
-80
-40
0
40
-0.2 0 0.2 0.4 0.6 0.8
dt (in)
T (kips)
Test
Model
Modeling of Chord Connector
=0.7
T Td
t
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April 23 2012PCI/NSF/CPFPART 1:21 of 34
Modeling of JVI Connector
dv
V V
Cyclic response
-20
-10
0
10
20
-0.6 -0.4 -0.2 0 0.2 0.4 0.6
dv (in)
V(k
ips)
TEST
-20
-10
0
10
20
-0.6 -0.4 -0.2 0 0.2 0.4 0.6
Model
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April 23 2012PCI/NSF/CPFPART 1:22 of 34
Modeling of Ductile Mesh
V, dv
-50
-25
0
25
50
-1.5 -1 -0.5 0 0.5 1 1.5
dv(in)
V (
kips
)
Test
-50
-25
0
25
50
-1.5 -1 -0.5 0 0.5 1 1.5
Model
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:23 of 34
Discrete FE models
Diaphragm Analytical Modelling
Ramp Cavity
Transverse inertial load Precast units
Nonlinear coupled springs and contact elements
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:24 of 34
Prototype Structure #1: Parking Garage
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:25 of 34
PDH Test
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:26 of 34
PDH Test Results: Flexure
-3000
-2500
-2000
-1500
-1000
-500
0
500
1000
1500
2000
-0. 0002 -0. 0001 0 0. 0001 0. 0002
rot
M (k
-in)
TestPredi ct
-8000
-6000
-4000
-2000
0
2000
4000
6000
-0. 0002 0 0. 0002 0. 0004 0. 0006 0. 0008
rot
M (k
-in)
TestPredi ct
-8000
-6000
-4000
-2000
0
2000
4000
6000
8000
-0. 0015 -0. 001 -0. 0005 0 0. 0005
rot
M (k
-in)
TestPredi ct
-6000
-4000
-2000
0
2000
4000
6000
-0. 0005 0 0. 0005 0. 001 0. 0015
rot
M (k
-in)
TestPredi ct
-10000
-8000
-6000
-4000
-2000
0
2000
4000
6000
8000
-0. 004 -0. 003 -0. 002 -0. 001 0 0. 001
rot
M (k
-in)
Predi ctTest
CH Service CH DBE CH MCE
CH Bi-dir DBE BK MCEJoint Flexural
Response
M
M
Weld Fracture
Minor Cracking
Major Cracking/Crushing
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:27 of 34
Shaking Table Structure
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:28 of 34
Test Comparison: Knoxville
Knoxville DBEδ
- 0. 8
- 0. 6
- 0. 4
- 0. 2
0
0. 2
0. 4
0. 6
0. 8
4 5 6 7 8 9
Ti me (s)
D(in
)
TestPredi ct i on
Diaphragm midspan roof drift
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:29 of 34
Phase III: Design Methodology Development
NEES/EERI Webinar
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Modeling of Evaluation Structure
Precast units: Plane stress element
Chord connector: Nonlinear springs
Shear connector: Nonlinear springs
Symmetryboundary
Column: 3D beam element
Spandrel: 2D beam element
Connector Elements
Moment frame 3D beam element
Shear wall3D shell element
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:31 of 34
Suite of Ground Motions
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
0 10 20 30 40
Time (s)
A (
g)
BK1BK2BK3BK4BK5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0 10 20 30 40 50
Time (s)
A (
g)
KN1
KN2
KN3
KN4
KN5
0
0.2
0.4
0.6
0.8
1
0 0.4 0.8 1.2T (s)
Sa (g)
MeanDesignN-6N-4N-2
Tflx
Trig
SDC E
SDC C
0
0.5
1
1.5
2
2.5
3
0 0.4 0.8 1.2
T (s)
Sa (g)
DesignMeanN=6N=4N=2
Trig,SW
Trig,FR
Tflx,SW
Tflx,FR
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:32 of 34
-0.2 0 0.2 0.4 0.6-600
-400
-200
0
200
400
600
Opening (in)
T (
k)
Ψ = 1.0Ψ = 1.5Ψ = 2.0Ψ = 2.5
Trial Design Factors
Chord connector
SDC E AR=3
T, δ
T
δ
Diaphragm Force Amplification Factor
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:33 of 34
Design Methodology Verification: Prototype Structures
Lbeam=48' L'=204' 48'
L=300'
60'
d=60'
60'
a=180'
25'8'
Lite wall
Shear wall
b=12'
Ramp Span Transverse
Longitudinal
North
South
RampLanding
Joint #: 1 2 3 4 5 6 7 8 9 10 11 12
West South
North East
16'
10'-6"
10'-6"
10'-6"
47'-6"
204'
4-Story Parking Structure
NEES/EERI Webinar
April 23 2012PCI/NSF/CPFPART 1:34 of 34
230'
147'
170'
South
North
West East
24.5'
24.5'
20'30'Joint # 1 2 3 4 5 6 7 8 9 10 11
30' 20' 20' 20' 20' 30'30' 30' 30'
230'
15'
106'
13'
15'
13'
13'
13'
13'
13'
13'
Design Methodology Verification: Prototype Structures
8-Story Office Building
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