Full-Scale Testing of Soft-Story Woodframe Buildings with Stiffness

Full-Scale Testing of Soft-Story Woodframe
Buildings with Stiffness-Based Retrofits
John W. van de Lindt, Pouria Bahmani,
Elaina N. Jennings
Colorado State University
Weichiang Pang and Ershad Ziaei
Clemson University
Gary Mochizuki and Steven Pryor
Simpson Strong Tie
Xiaoyun Shao
Western Michigan University
Mikhail Gershfeld
Cal-Poly Pomona
Michael D. Symans and Jingjing Tian
Rensselaer Polytechnic Institute
Douglas Rammer
USDA Forest Products Laboratory
Tenth U.S. National Conference on Earthquake Engineering
Frontiers of Earthquake Engineering
July 21-25, 2014
Anchorage, Alaska
The NEES-Soft Project Team & Practitioner
Advisory Committee
Project Team
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Colorado State University: Prof John W. van de Lindt; Pouria Bahmani, Ph.D. Student
Clemson University: Prof WeiChiang Pang; Ershad Ziaei, Ph.D. Student
Western Michigan University: Prof Xiaoyun Shao; Chelsea Griffith, M.S. Student
Rensselaer Polytechnic Institute: Prof Michael D. Symans, Prof David V. Rosowsky; Jingjing
Tian, Ph.D. Student
Cal Poly – Pomona: Prof Mikhail Gershfeld; Robert McDougal. M.S. Student; Nathan
Summerville, B.S. Student
SUNY at Buffalo: Prof Andre Filiatrault
Structural Solutions Inc.: Gary Mochizuki
U.S. Forest Products Lab.: Douglas Rammer
Tipping Mar: David Mar
South Dakota State University: Prof Shiling Pei
Cal Poly – SLO: Prof Charles Chadwell
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Practitioner Advisory Committee
Laurence Kornfield - City of San Francisco - CAPSS
Kelly Cobeen - WJE
Steve Pryor - Simpson Strong Tie
Tom Van Dorpe - VanDorpe Chou Associates, Inc.
Doug Thompson - STB Structural Engineers
Doug Taylor - Taylor Devices
Janiele Maffeti, California Earthquake Authority
Rose Grant, State Farm Insurance
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J.W. van de Lindt
Motivation for NEES-Soft
”Seismic Risk Reduction for Soft-Story Woodframe Buildings”
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Many buildings built prior to the 1970s are prone to
collapse during major earthquake event due to
insufficient lateral resistance of their first story.
EERI
Community Action Plan for Seismic Safety (CAPSS)
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43 to 80 percent of the multi-story wood-frame buildings will be
deemed unsafe after a magnitude 7.2 earthquake
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25% of these buildings would be expected to collapse
ATC 71.1 Project (FEMA P695)
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Develop seismic retrofit requirements for soft-story wood-frame
buildings in seismically active regions of the United States
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Focusing primarily on Northern and Southern California and the
Pacific Northwest
J.W. van de Lindt
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NEES-Soft: Seismic Risk Reduction for Soft-Story
Woodframe Buildings
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Five-university-industry NSF-funded collaboration
Develop better understanding of soft-story woodframe behavior
through numerical analyses and experimental testing
Experimental validation of FEMA P807
Performance-based retrofit methodology and techniques
Develop better models of woodframe collapse mechanisms
A. Buchanan
Existing Buildings
© Mikhail Gershfeld
© Steve Pryor
NEES-Soft Test Program Overview
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Assembly Testing
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CLT panels (University of Alabama)
Wall finish combinations (Colorado State University)
Reversed cyclic knee-brace testing (Cal-Poly SLO) (Gershfeld, this session)
Distributed knee brace shake table testing (Colorado State University)
Full-Scale Whole Building Testing
– Three-story slow hybrid test building at NEES@Buffalo
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Cross Laminated Timber (P807)
Distributed knee-brace (First story only) (Gershfeld, this session)
Cantilevered column (P807)
Viscous damper devices (First story only) (Symans, this session)
Shape memory alloy + wood structural panels (including ATS) (PBSR) (Jennings, Thursday)
Steel special moment frame + wood structural panels (including ATS) (PBSR)
– Four-story shake table test building at NEES@UCSD
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Cross Laminated Timber (P807) (van de Lindt, this session)
Steel SMF (P807)
Steel SMF + wood structural panels (including ATS) (PBSR) (van de Lindt, this session)
Viscous damper devices + wood structural panels (including ATS) (PBSR) (Symans, this session)
Un-retrofitted (van de Lindt, this session)
2 Types of Retrofits
FEMA P-807 Method Retrofit
Applied the P807 weak story
Tool (WST) using wall sheathing
Combination
General concept:
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Only first story is retrofitted
Keep ISD below (believed) onset of
collapse which is set at approx 4%
Limit the difference in CR between first
and next story to 5%.
First two phases
• Cross Laminated Timber rocking
walls
• Steel SMF
Performance-based seismic
retrofit (PBSR)
(Two approaches used)
Extension of Direct Displacement
Design (DDD) developed in
NEESWood project
General concept 1:
Remove torsion at first story with
transverse retrofit
Apply simplified DDD (Pang et al,
2010) to target 50% PNE at 2%
ISD
Steel SMF+ WSP
General concept 2:
Nonlinear time history analysis
with trial and error
Viscous fluid dampers
The NEES-Soft UCSD Team
John van de Lindt, PI
Colorado State Univ.
Michael Symans, Co-PI
RPI
Michael Gershfeld, Co-PI
Cal-Poly Pomona
Weichiang
Pang, Co-PI
Clemson Univ.
Xiaoyun Shao, Co-PI
W. Michigan Univ.
Steve Pryor, Collab.
Simpson Strong-Tie
Sandra, REU
Gabriel, REU
Gary Mochizuki, Collab.
Structural Solutions Inc.
Pouria Bahmani, Ph.D. Candidate
Colorado State Univ.
Connie, REU
Faith, REU
Rocky, REU
Jingjing Tian,
Ph.D. Candidate
RPI
The lifecycle of the test building
Construction
Recycling
and Disposal
Ready for testing
Collapse Testing
Cross laminated
timber rocking
walls
Viscous damping
devices + WSP (PBSR)
Steel SMF (FEMA P807)
Steel SMF + WSP (PBSR)
Phase I: Cross Laminated
Timber Rocking Walls
Applying the FEMA P807 Methodology
CLT Retrofit Location
1-CLT Panels
2-CLT Panels
Ø 16mm (85 in.)
Threaded Rods
Ø 16 mm (85 in.)
Threaded Rods
2-CLT Panels
2-CLT Panels
CLT Retrofit Location
CLT Test - Takeaways
Peak response of approximately 1.5 inches
Response isolated at 1st story
P807 methodology seems appropriate for soft-story retrofit
NEES-Soft test report forthcoming on wall sheathing
combinations
Using 50% MCE for P807 target level not unreasonable
In 50% MCE, mostly non-structural damage
In MCE, predict substantial structural damage but no
collapse
Phase III: Steel SMF + WSP
Performance-Based Seismic Design/Retrofit
Procedure With Torsion – Simplified Method
Check For Torsional Stiffness
PBSR - First Story
ATS
ATS
WSW - A
1
2
3
4
5
60
ATS
250
50
200
40
150
30
100
20
Y
ATS
WSP-1
WSW
-1
3000
50
0
0
X
25
50
75
10
100
125
0
150
60
40
20
0
-20
-40
-60
2
1
0
-1
-2
6
4
2
0
-2
-4
-6
2
1
0
-1
-2
40
6
4
2
0
-2
-4
-6
-1.87 ʺ < 1.92 ʺ (or 2%)
1.29 ʺ
32.8
0
10
20
30
-2.3
1.0
0
Max. Displacement, (in.)
2
3
4
5
400
3
2
Test
Test
Test
Test
Test
1
0
0
25
0.2
0.1
0
-0.1
-0.2
40
0.04 ʺ
10
20
30
Roof Displacement, (in.)
50
75
100
125
Max. Displacement, (mm)
9
10
11
12
13
150
Base Shear, (kN)
Story Number
1
-0.09 ʺ
Perpendicular to shake
Parallel to shake
40
0.2
0.1
0
-0.1
-0.2
Inter-Story Drift, (inch)
60
40
20
0
-20
-40 -47.4
-60
-4
-2
0
2
4
(4.49,63.6) (114,283)
75
200
25
0
Base Shear, (kip)
Inter-Story Drift, (mm)
Global Response to Loma Prieta Ground Motion @ MCE Level
-25
-200
-400
(-83,-211) (-3.27,-47.4)
-100
0
100
Roof Displacement, (mm)
-75
PBSR Test - Takeaways
Peak response of approximately 2 inches (not
only shear deformation)
Significantly larger response moved up to 3rd
story
Models did predict this effect
Survived MCE with NO structural damage
GWB damage easily repairable
Would survive much more intense MCE
Phase V: Collapse Testing
The Collapse Motion
Scaled to Sa = 0.4 g
100
Cape Mendocino
75
2
25
1
0.2 0.4 0.6 0.8
1
1.2 1.4 1.6 1.8
300
0
2
100
4
50
2
0
0
0.2 0.4 0.6 0.8
1
1.2 1.4 1.6 1.8
12
100
4
800
6
16
8
1000
Cape Mendocino
150
Cape Mendocino
Superstition Hills
200
0
0
Scaled to DBE Level , Sa = 1.2 g
200
100
50
0
-50
-100
100
50
0
-50
-100
300
200
100
0
-100
-200
-300
400
3
50
0
0
Scaled to Sa = 0.9 g
500
600
400
0.2 0.4 0.6 0.8
1
1.2 1.4 1.6 1.8
Scaled to MCE Level , Sa = 1.8 g
Cape Mendocino
Loma Prieta
Superstition Hills
32
24
16
200
0
2
0
0
0
2
8
1.2 1.4 1.6 1.8
0
2
Loma Prieta @ MCE Level
2
0.2 0.4 0.6 0.8
72.1
1
0
-2
Cape Mendocino @ MCE Level
2
0
-2
-58.8
276.6
Superstition Hills @ MCE Level
6
0
-6
0
5
10
15
20
Time, (sec.)
25
30
35
40
1.0
0.5
0
-0.5
-1.0
1000
500
0
-500
-1000
300
200
100
0
-100
-200
-300
1000
500
0
-500
-1000
0.2
0.1
0
-0.1
-0.2
0.206
0
40
0
40
-12.7
0
0
313.7
-29.3
40
0
80
-58.9
120
120
-489.5
72
160
160
-817.2
277
200
280
138.9
280
-441.5
240
0.05
200
-422.3
240
-470.3
0.01
280
240
200
-102
-0.419
240
200
160
-0.01
-0.86
200
160
95.9
0.01
80
459.3
120
61.8
0.01
40
-39.1
-0.974
160
120
80
47.8
0.901
120
80
40
21.7
0.557
80
238.6
107.1
0
0.441
280
0.05
240
-0.856
320
-821.6
320
276
320
635.9
320
-0.19
280
320
Response of First Story to Superstition Hills @ MCE Level
1000
750
500
250
0
-250
-500
-750
-1000
0
1000
750
500
250
0
-250
-500
-750
-1000
0
(a)
Superstition Hills – Test No. 6
350
-470.3
10
(b)
20
635.9
30
Superstition Hills – Test No. 8
String pot. destroyed,
Building collapsed
other direction
400
10
20
Time (sec)
30
30
20
10
0
-10
-20
-30
40
30
20
10
0
-10
-20
-30
40
Concluding Remarks
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The FEMA P-807 retrofit guidelines provide a good alternative to fully code compliant
retrofits when constraints, either financial or logistical, prevent a more comprehensive
(e.g. code compliant or performance-based) approach.
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The un-retrofitted building was subjected to earthquakes which resulted in just slightly
more than 4% inter-story drift. Thus, for these earthquake motions (Cape Mendocino
and Loma Prieta) the P-807 retrofitted building would likely have about 2.5% to 3%
drift and be very unlikely to collapse and repairable.
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The PBSR retrofits enabled distributed seismic demand over the height of the
structure and resulted in very good performance; and would likely allow the structure
to survive a much more intense earthquake.
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All tested retrofits were able to provide the desired performance and were deemed
viable candidates for retrofit of soft-story buildings; they did, however, offer a
substantial range of cost and perofrmance.
Thank you.
This material is based upon work supported by the National Science Foundation
under Grant No. CMMI-1314957 (NEES Research) and NEES Operations. Any
opinions, findings, and conclusions or recommendations expressed in this material
are those of the investigators and do not necessarily reflect the views of the
National Science Foundation. In kind and cash contributions toward this research
were also provided by Simpson Strong-Tie, the USDA Forest Products Laboratory,
Taylor Devices, and SEAOSC.
The presenter sincerely acknowledges senior personnel David V. Rosowsky at University of Vermont, Andre Filiatrault at
University of Buffalo, Shiling Pei at South Dakota State University, and Charles Chadwell at Cal Poly – SLO. A special thank
you to Asif Iqbal (BRANZ) for his collaboration.
A special thank you to all of the REU students Sandra Gutierrez, Faith Silva, Karly Rager, Gabriel Banuelos, Rocky Chen,
Philip Thompson, and Connie Tsui. Others that have helped include Asif Iqbal, Vaishak Gopi, Steve Yang, Ed Santos, Tim
Ellis, Omar Amini, and Russell Ek. Finally, our sincere thank you to NEES and all site staff and site PI’s at NEES@UCSD
and NEES@UB for their help getting the tests ready.
Professor John W. van de Lindt
[email protected]
Acknowledgements
This material is based upon work supported by the National Science Foundation under Grant No. CMMI-1041631 (NEES
Research) and NEES Operations. Any opinions, findings, and conclusions or recommendations expressed in this material
are those of the investigators and do not necessarily reflect the views of the National Science Foundation.
The presenter kindly acknowledges the Co-Principal Investigators of the NEES-Soft project: Michael D. Symans at
Rensselaer Polytechnic Institute, WeiChiang Pang at Clemson University, Xiaoyun Shao at Western Michigan University,
Mikhail Gershfeld at Cal Poly – Pomona, and senior personnel David V. Rosowsky at Rensselaer Polytechnic Institute, Andre
Filiatrault at University of Buffalo, Gary Mochizuki at Structural Solutions Inc., Shiling Pei at South Dakota State University,
Douglas Rammer at U.S. Forest Products Lab., David Mar at Tipping Mar, and Charles Chadwell at Cal Poly – SLO, and the
graduate students working on the project, Pouria Bahmani, Jingjing Tian, and Ershad Ziaei. A special thank you to Asif Iqbal
(BRANZ) for his collaboration and Steve Pryor for his collaboration through Simpson Strong-Tie on the SSMF design,
installation, and testing.
Thank you to Simpson Strong-Tie, SEAOSC, U.S. Forest Products Lab, NEES@UCSD, NEES@UB and all respective
personnel.
A special thank you to all of the REU students Sandra Gutierrez, Faith Silva, Karly Rager, Gabriel Banuelos, Rocky Chen,
Philip Thompson, and Connie Tsui. Others that have helped include Asif Iqbal, Vaishak Gopi, Steve Yang, Ed Santos, Tim
Ellis, Omar Amini, and Russell Ek. Finally, our sincere thank you to NEES and all site staff and site PI’s at NEES@UCSD
and NEES@UB for their help getting the tests ready.

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