1. Development of a Diaphragm Seismic Design Methodology (DSDM) for Precast Concrete Structures
Robert Fleischman and Ge Wan, University of Arizona
Clay Naito, Richard Sause and Liling Cao, Lehigh University
José Restrepo and Matt Schoettler, UC-San Diego
S.K. Ghosh, S.K. Ghosh Associates, Inc.

2. Outline of Presentation
Background History
Background History
Rationale for NEES-type Research
Research Approach
Industry Interaction
Year 1 Activities

3. Problem Statement
The precast concrete industry has mounted a sustained effort to develop seismic-resistant lateral force resisting elements.
NSF PRESSS program

4. 1994 Northridge earthquake
Problem Statement
However, the poor performance of precast concrete diaphragms in recent earthquakes underscores the importance of examining the entire precast structural system.
1994 Northridge earthquake

5. PCI Solicitation and Award
In October 2002, PCI distributed an RFP for the development of a comprehensive seismic design methodology for floor diaphragms in precast concrete buildings.
A multi-university research team comprised of investigators from the University of Arizona (UA), University of California at San Diego (UCSD), and Lehigh University (LU) was selected.

6. * Participated in proposal stage only.
DSDM Consortium
PCI, IAP *
DSDM Task Group
* Participated in proposal stage only.

7. Producer Members Blakeslee Prestress, Inc. High Concrete Structures
Precast/Prestressed Concrete Manufacturers Association of California
Spancrete, Inc.
Tindall-Virginia
Ivy Steel & Wire
Metromont Prestress

8. NSF Funding
Proposal submitted to National Science Foundation (NSF) in 2003.
Precast Industry Contribution:
$200,000 in direct funding
$60,000 in travel and logistical support
$75,000 for consulting services
$91,000 in specimen donations
Requested budget: approximately $500,000
DSDM Consortium awarded NSF grant in 2004.

9. Project Objective and Scope
Develop a Seismic Design Methodology for Precast Concrete Diaphragms including:
Topped and Pretopped Diaphragms
Hollow Core and Double Tees Precast Units
Low to High Seismic Zones
Existing and Promising Reinforcement Details

10. Outline of Presentation
Background History
Rationale for NEES-type Research
Rationale for NEES-type Research
Research Approach
Industry Interaction
Year 1 Activities

11. Challenges in developing a DSDM Floor Inertial Loads
Equivalent lateral force (ELF) design procedures currently in use may significantly underestimate diaphragm inertial forces.
After Fleischman and Farrow, EQ Spectra 2001; also see Rodriguez and Restrepo EE & SD 2002, Eberhard and Sozen, Miranda, etc.

12. Discretely connected units
Challenges in Developing a DSDM
Jointed Diaphragms
Precast diaphragms possess several characteristics that make a DSDM challenging:
Complex Force Paths
Long floor spans
Fpx
-0.6
0.6
-25
Discretely connected units

13. Challenges in developing a DSDM
Inelastic deformations and diaphragm flexibility
Deformation patterns that may cause complex internal force combinations.
Large inter-story drifts away from primary LFRS elements.
High localized deformation. demand in joints between precast units due to twist.
After Fleischman and Farrow, EQ Spectra 2001; EE & SD 2000

14. Challenges in developing a DSDM
The diaphragm seismic response shown is a complex interaction of :
System behavior (the overall structure)
Component behavior (the floor diaphragms)
Section behavior (diaphragm panels and joints)
Detail behavior (individual hardware/reinforcement)
Previous research attempts have typically focused on only one of these particular “levels” at a time.

15. Previous “System-Level” Research
2D (in the plane of the floor) Finite Element (FE) models of the floor diaphragm are analyzed for capacity using nonlinear pushover techniques.
The diaphragm characteristics (stiffness, strength, ductility) obtained are used to create simple structural models to obtain demands (forces, drift, ductility) under seismic loading.
Diaphragm forces and force paths estimated entirely through analytical simulation
The analytical simulations in turn depend heavily on tests of individual joint reinforcing details under highly idealized loading conditions.

16. Outline of Presentation
Background History
Rationale for NEES-type Research
Research Approach
Research Approach
Industry Interaction
Year 1 Activities

17. Integrated Analysis and Experimentation
Research Approach:
Integrated Analysis and Experimentation
(EQ) Demand
Verified By
Capacity
UA Analyses link UCSD structure test with LU detail tests.
Load Input
Model Input

18. Outline of Presentation
Background History
Rationale for NEES-type Research
Research Approach
Industry Interaction
Industry Interaction
Year 1 Activities

19. DSDM Task Group Set the physical scope
Selection of prototype structures and representative details
Transformation of research results into an appropriate design methodology
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
Paul Johal
Research Director
PCI
Joe Maffei
Engineering Consultant
Rutherford & Chekene
Engineers
Susie Nakaki
President
The Nakaki
Bashaw Group, Inc.
Harry Gleich
Vice President
Metromont Prestress

20. Prototype Structures PS#1: 4-story side-by-side parking garage
PS#2: 4-story helical parking garage
Distributed shear walls
PS#1: 4-story side-by-side parking garage
Ramp
Perimeter shear walls
PS#5: two-way moment frame parking deck
PS#3: 5-story L-wing office building
Distributed cores
PS#4: 4-story office building/school
Central core

21. Seismic Design Sites Candidates sites selected by DSDM TG Moderate
High
Near Field
Soft Soil

22. Prototype Structure Design
PS#1: Moderate Seismic Zone (Knoxville)
Vertical distribution
Design Code IBC 2003
Ss 0.58 S
Soil Site Class C
Fa 1.17
Fv 1.65
Sms= Fa Ss 0.68
Sm1= Fv S
SDS= 2/3 Sms 0.45
SD1= 2/3 Sm1 0.16
EW Shear Walls R=5, W0=2.5, Cd=4.5
NS Light Framed Walls R=4.5, W0=2.5, Cd=4
Seismic Design Category C
Cs 0.09
Cs,min
Cs,max
Base shear kips
Diaphragm design
Collectors
Chord Steel
Shear Reinf

23. Representative Diaphragm Details
Primary diaphragm details (web, chord, collector, wall anchorage)
DT/Spandrel (PS#3)
DT/IT (PS#1)
IT/Wall (PS#1)
Spandrel/Col. (PS#1)
Secondary details (spandrels, floor beams, columns)
DT chord (PS#1)
DT web (PS#2)
DT/Wall (PS#2)
DT along Wall (PS#2)

24. Outline of Presentation
Background History
Rationale for NEES-type Research
Research Approach
Industry Interaction
Year 1 Activities
Year 1 Activities

25. Integration and Flow of Activities1 2 1 4 2a 2
Diaphragm Characteristic 3a 3

26. Nonlinear spring and contact elements in ANSYS
Analytical Program: Diaphragm FE Model
Nonlinear spring and contact elements in ANSYS
2D FE model: PS#1
Properties based on test data of details
Year 1: existing tests
Year 2: LU test

27. JVI, Concrete Technology Co., Dayton; Venuti, Oliva, et.al.
Lehigh Database
Monotonic Shear Response
cover plate
JVI, Concrete Technology Co., Dayton; Venuti, Oliva, et.al.

28. Combined Forces on Connectors
Ratio of shear to tension in the web reinforcement.

29. Combined Force Tests
Effect of Tension and Cycling on Shear Response: (Oliva 98)
Monotonic Shear with Tension
Cyclic vs. Monotonic Shear

30. Project Year 1: Lehigh University (LU) Tests
The three actuator load frame built at LU possesses the ability to provide proportional and non-proportional loading under mixed mode (displacement or force) control.
Test setup
Loading protocol

31. Representative Detail
Building the Diaphragm Model
Representative Detail
LU test “A”
Test
Model
Plastic link elements to match monotonic tension.
Contact Element
Nonlinear shear spring to supplement shear strength T V
Hairpin

32. Connector Element Calibration
Comparison w/ M. Oliva’s test results U-Wisc Mad (1998)
Angled bars T V

33. Cyclic Shear Comparison
Plate w/rebar (Oliva 1998)
µ=1
µ=1.5
µ=2 T V

34. Project Year 1: UCSD Shaking Table Test
Structural level examination:
Table Outrigger
Platen
1:2 to 1:3 scale model
3-story specimen to include 3 floor systems:
Untopped double tee
Topped double tee
Hollow core

35. Overall Project Objective
An effective seismic design methodology for precast concrete diaphragms:
Accurate Design Forces
Method for Estimating Internal Forces
Stiffness Calculations
Limits on Diaphragm Flexibility
Knowledge of Detail Capacities
Structural Integrity Detailing

36. Thank you!