1. Development of Self-Centering Steel Plate Shear Walls (SC-SPSW)
Jeff Berman
Assistant Professor
University of Washington

2. NEESR-SG: Steel Plate Shear Wall Research
Jeff Berman and Laura Lowes
Larry Fahnestock
Michel Bruneau
Graduate Students:
UW: Patricia Clayton, David Webster UIUC: Dan Borello, Alvaro Quinonez UB: Dan Dowden
K.C. Tsai
Rafael Sabelli
Sponsored by NSF through the George E. Brown NEESR Program
Material Donations from AISC

3. Project Overview a ~43° Resilient SPSW
Analysis and Verification of Performance
Subassemblage Testing
Shake Table
Testing
Full-Scale Testing
Fill Critical Knowledge Gaps a
~43°
Cyclic Inelastic Tension Field Action
SPSW Damage States and Fragilities
Coupled SPSW
Testing (MUST-SIM)

4. US Northridge Earthquake (1994)
Motivation
Current U.S. seismic design codes
Life Safety and Collapse Prevention
Maximum Considered Earthquake (MCE)
U.S. Earthquakes since 19701:
Only 2 people per year die due to structural collapse
$2 billion per year in economic loss
US Northridge Earthquake (1994)
Haiti Earthquake (2010)
1 ATC-69 (2008)

5. Resilient SPSWs: Motivation
Steel Plate Shear Walls (SPSWs):
Thin web plates: tension field action
High initial stiffness
Ductile
Distributed yielding
Replaceable “fuses” (web plates)
However,
Damage in HBEs and VBEs
not as easy to repair/replace
How can we limit damage to HBEs and VBEs to provide a quicker return to occupancy following an earthquake?
(Vian and Bruneau 2005)

6. Resilient SPSW: SPSW+ PT Frame
VSPSW
VPT D D
VR-SPSW
Unloading
Plate yields
Connection
Decompression
Plates Unloaded
1st Cycle
2nd Cycle D
Connection
Recompression
Previous PT Connection Work: Garlcok et al. 2002, Christopoulos et al., 2002

7. SC-SPSW Research Overview
Analytical Research
Performance-Based Design Procedure
Analysis and Verification of Performance
System Behavior
Subassembly Testing
(U. of Washington)
Experimental Research
Shake Table Testing
(U. at Buffalo)
Full-scale Testing
(NCREE, Taiwan)

8. R-SPSW Mechanics Distributed loads on frame from web plates
Compression of HBE from three components: PT
Web plate loads on VBE
Web plate loads on HBE

9. Performance-Based Design
V2/50
D2/50
First occurrence of:
PT rupture
Excessive PT yielding
Excessive frame yielding
Excessive story drifts
Collapse
Prevention
V10/50
D10/50
First occurrence of:
PT yielding
Frame yielding
Residual drift > 0.2%
Repair of Plates Only V
D50/50
V50/50
Plate yielding
No Repair
Vwind
Connection decompression D

10. Analytical Model Nonlinear model in OpenSees
SPSW modeled using strip method:
Tension-only strips with pinched hysteresis
Strips oriented in direction of tension field

11. Analytical Model (cont.)
PT connection model:
Compression-only springs at HBE flanges
Rocking about HBE flanges
Shear transfer
Diagonal springs
PT tendons
Truss elements with initial stress (Steel02)
HBE
VBE
Rigid offsets
Physical Model
Analytical Model
Compression-only springs at HBE flanges
Diagonal springs to transfer shear

12. Dynamic Analyses
3 and 9 story prototypes based on SAC buildings: 4-6 SPSW bays
Each model subjected to 60 LA SAC ground motions representing 3 seismic hazard levels
50% in 50 year
10% in 50 year
2% in 50 year
Used OpenSeesMP to run ground motions in parallel on TeraGrid machines
Processor = 0
Processor = 1
Ranger
R-SPSW model
Processor = n-1

13. Analytical Summary All performance objectives met !!!
Results for typical 9-story SC-SPSW
designed WITHOUT optional 50% in 50 year “No repair” performance obj. V D
V10/50
D10/50
V2/50
D2/50
D50/50
V50/50
Vwind
Performance Objectives:
No plate repair (Story drift < 0.5%) in 50/50
Recentering (Residual Drift < 0.2%) in 10/50
Story drift < 2.0% in 10/50 (represents DBE)
Limited PT, HBE, and VBE yielding in 2/50
No Repair
Collapse
Prevention
Repair of Plates Only
All performance objectives met !!!

14. UW Component Tests Reaction Blocks Pin to Allow VBE Rotation
Roller to Allow Gap Opening
Pin to Allow VBE Rotation
Target Deformation of Specimen
Laboratory Configuration
Subassemblage

15. R-SPSW Testing Connection decompression Development of tension field
Flag-shaped hysteresis
Residual web plate deformation after test

16. Comparison of Parameters
Change in number of PT strands
Change in web plate thickness Kr
Affects recompression stiffness, Kr, due to change in PT stiffness
Affects decompression moment
Affects system strength and energy dissipation
Affects post-decompression stiffness

17. Comparison with Idealized Response
1st Cycle
2nd Cycle
VSC-SPSW D
Plate yields
Unloading
Connection
Decompression
Recompression
Plates Unloaded
More energy dissipation than assumed
Some “compressive” resistance due to geometric stiffening

18. Web Plate Behavior Study
FE modeling
Residual Load
Experimental testing
Pins
~25% of yield strength
(Webster 2011)

19. Comparison with Models
OpenSees model
With and without compressive resistance in strips
Future improvements to strip model:
Modify strain hardening rules to account for cyclic yielding
Quantify compression in SPSW strip model

20. Kim and Christopoulos (2008)
Frame Expansion
As PT connection decompresses, VBEs spread apart
Garlock (2002)
Kim and Christopoulos (2008)
Can cause floor damage or increase frame demands if beam growth is restrained, especially at 1st floor beam

21. Accommodation of Frame Expansion
Garlock (2007)
Flexible collector beams connecting PT frame and composite slab
Applies additional point loads along beam
Damage to collector beams
Kim and Christopoulos (2008)
Sliding interface between slab and beams
Eliminates slab restraint

22. Elimination of Frame Expansion
Rocking about HBE centerline (Pin)
NewZ-BREAKSS
Rocking about top flange only

23. Testing at NEES@Buffalo
Quasi-Static tests
1/3 scale, 3-story
Various PT connection details
Full plate and Strips

24. Comparison of Behavior
Flange rocking provides better re-centering because of decompression moment
NewZ-BREAKSS prevents floor damage due to frame expansion.

25. UB Shake Table Tests 6 degree-of-freedom shake table
Same specimens as quasi-static tests
Scheduled for completion in fall 2012

26. System-level Testing
National Center for Earthquake Engineering (NCREE) in Taiwan
2-story, full scale SC-SPSW
Single actuator
Quasi-static loading
Summer 2012

27. NCREE Specimens
PT column base
Column can rock about its flanges

28. NCREE Specimens PT column base 2 specimens
Column can rock about its flanges
2 specimens
Flange rocking HBEs
NewZ-BREAKSS Connection
(Top flange rocking HBEs)

29. Conclusions Performance-based design procedure developed for SC- SPSW:
Elastic behavior during frequent events
Web plate yielding and recentering during DBE events
Collapse prevention during MCE events
Analytical studies show SC-SPSWs are capable of meeting proposed performance objectives
Experimental subassembly tests show ‘simple’ models are conservative and have room for improvement
Future testing will verify performance on system level

30. Thank You
To provide insight into my background, here are some projects I’ve worked on
Questions?