Transcript CEE 289: Random Vibrations Introduction

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Seismically Enhanced Non-Structural
Partition Walls for Unibody
Residential Construction
Gregory Deierlein (PI)
Eduardo Miranda (Co-PI)
Scott Swensen
Stanford University
Benjamin Fell (Co-PI)
Amy Hopkins
California State University, Sacramento
Quake Summit 2012
The George E. Brown Network for Earthquake Engineering Simulation
(NEES)
July 12th, 2012
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Introduction
Traditional light-weight framed structures:
• provide a high degree of life safety
• are vulnerable to costly earthquake damage
- About $20 billion in losses occurred to light-frame residential
structures during the Northridge Earthquake
• can lead to many displaced persons
when damaged
- The 1994 Northridge Earthquake
destroyed or heavily damaged
60,000 housing units
www.impactlab.net/wp-content/uplopads/2010/03/fiolmore-house.jpg
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Conventional Light-Frame Construction
Current design methodology:
1. Design structural walls (i.e. plywood or OSB) to resist entire design
lateral loads
2. Add architectural finishes such as gypsum partitions and stucco cladding,
neglecting or heavily discounting lateral resistance
R = 6.5
V
R=2
VDBE
R=2
VR = 2
R = 6.5
VR = 6.5
DBE, 2 DBE, 6.5
Created by E. Miranda
www.nhmodularhomes.com/house_cut_away.htm

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Conventional Light-Frame Construction
This design approach creates problems because in light framed
construction, the ultimate load is achieved at large and damaging drifts
peak lateral strength
≈ 2% drift
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onset of damage
≈ 0.2% drift
Racking Load (kN/m)
4
2
0
-2
-4
-6
-2.5
-1.5
-0.5
0.5
1.5
2.5
Drift (%)
www.flickr.com/photos/encouragement/3566839185
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Opportunities to Improve Light-Frame Construction
Alternate design methodology:
• Design structural and architectural building components to work together
in a ‘unibody’ manner to resist earthquake loads and deformations
www.imperialclub.com/Yr/1966/SpottersGuide/index.htm
majesticspeed.com/wp-content/uploads/2010/12/Car-Unibody.jpg
This method is economical because finishes wouldn’t have to be added, they
just must be better integrated into the structural system
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Opportunities to Improve Light-Frame Construction
This approach makes sense for light-framed buildings because:
• low-rise framed structures are light
• wall area is plentiful – increased strength
is inexpensive
• structural and architectural components are integral
• most components are drift sensitive
• for short period buildings, drifts are especially sensitive to lateral strength
and stiffness
Ruiz-Garcia and Miranda 2003
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Unibody Design Concept
• Design spectrum for Los Angeles, site class D, 5% damping
Conventional Framed Building
R = 6.5
Ω=3
CR ≈ 1.6 (FEMA 440)
Enhanced Framed Building
R=1
Ω=1
CR ≈ 1
1.6
1.4
R/Ω
1.2
CR
Sa (g)
1
0.8
0.6
0.4
0.2
0
0
0.1
0.2
Period (s)
0.3
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Research Objectives
1.
Develop improved limited ductility light-frame design concepts which
increase lateral structural strength and stiffness in an economical manner
2.
Create and verify computational models that evaluate the seismic
performance of enhanced ‘unibody’ systems
3.
Formulate design methods and tools that consider (1) life safety and (2)
life cycle costs and loss of building functionality during seismic events
4.
Develop cost-effective base isolation systems for low-rise light framed
structures in areas of high seismic hazard
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Components of Light-framed Walls
Sheathing-to-framing Fastener
Edge Panel Joint
Finished Wall
Flat Panel Joint
1.
2.
3.
Conventional mechanical
fasteners
Novel mechanical fasteners
(Maxiscrew by Ben Schmid)
Adhesive fastening systems
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Mechanical Fastener Tests – ⅝” Type X GWB
Monotonic Backbone
Δ = 1.3 mm
(0.05”)
Δ = 2.2 mm
(0.09”)
Load Per Fastener (kN)
1
Enhanced Screw
0.9
+16%
0.8
Δ = 5.2 mm
(0.20”)
Coarse Threaded
0.7
0.6
0.5
0.4
Δ = 10 mm
(0.40”)
0.3
0.2
0.1
0
0
Δ = 3.2 mm
(0.13”)
10
20
30
Displacement (mm)
40
50
Δ = 25 mm
(1.00”)
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Adhesive Gypsum-to-Wood Connections
Monotonic Backbone
Equiv. Load Per Fastener (kN)
4
Adhesive + Screws
3.5
Adhesive
3
2.5
Coarse Threaded
+4.9x
2
+5.5x
1.5
1
0.5
0
0
0.5
1
1.5
Displacement (mm)
2
2.5
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Adhesive Gypsum-to-Steel Connections
Equiv. Load Per Fastener (kN)
Monotonic Backbone
1.6
1.4
Adhesive + Screws
+2.9x
Adhesive
+4.7x
1.2
Fine Threaded
1
0.8
0.6
0.4
0.2
0
0
0.5
1
1.5
Displacement (mm)
2
2.5
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Components of Light-frame Residential Structures
Sheathing-to-framing Fastener
Edge Panel Joint
Finished Wall
Flat Panel Joint
1.
2.
3.
Conventional wall with coarse threaded screws
Wall with enhanced mechanical fasters
Wall with adhesive fastening and enhanced
screws
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Gypsum Sheathed Wall Tests – Wood Framing
• Cyclic loading of 1.22 m (4 ft) square walls
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4
Racking Load (kN/m)
Coarse
Threaded
Screws
8
0
-4
-8
-12
Enhanced
Fasteners
8
4
0
-4
-8
-12
-2
-1
0
1
2
-2
-1
0
Drift Ratio (%)
Drift Ratio (%)
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Racking Load (kN/m)
Racking Load (kN/m)
12
Adhesive +
Screws
8
4
0
-4
-8
-12
-2
-1
0
Drift Ratio (%)
1
2
1
2
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Gypsum Sheathed Wall Tests – Wood Framing
Cyclic Skeleton
+4.2x
12
SDR = 0.21%
SDR = 0.42%
Racking Load (kN/m)
+90%
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SDR = 0.94%
4
IBC/SDPWS Value (LRFD)
0
Adhesive + Screws
-4
+
Enhanced Screw
SDR = 2.0%
-8
Coarse Threaded
-12
-2
-1
0
Drift Ratio (%)
SDR = 0.63%
1
2
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Gypsum Sheathed Wall Tests – Steel Framing
Cyclic Skeleton
Racking Load (kN/m)
12
8
4
0
Adhesive + Screws
-4
+
Fine Threaded
-8
-12
-2
-1
0
Drift Ratio (%)
1
2
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Ongoing Testing of Gypsum and Stucco Clad Walls
Cyclic loading of 2.44 m (8 ft) tall walls is currently being carried out.
Testing variables include:
• sheathing (gypsum & stucco) and framing (wood and steel) material
• use of adhesives
• wall perforations and geometry
• presence and configuration of end returns
• configuration of holdowns and anchorages
Racking Load (kN/m)
12
8
4
0
Conventional
Adhesive
Adhesive with Blocking
-4
-8
-12
-2
-1
0
Drift (%)
1
2
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Finite Element Wall Analysis
0.9
Pinching4 Backbone
0.6
0.5
0.4
0.3
0.2
0.1
Load Per Fastener (kN)
Test Results (3 Repetitions)
0.7
Load Per Fastener (kN)
Fit hysteretic model
to component
behavior for fasteners,
adhesive, panel joints,
and holdowns
0.8
0.8
0.4
0.2
0
-0.2
Test Data
-0.4
Pinching4 Model
-0.6
-0.8
0
0
10
20
30
40
Displacement (mm)
Individual
fasteners
Build framing and
sheathing. Use
modeled components
to connect elements
0.6
Panel joint
Holdowns and
anchorages
-60
-40
-20
0
20
Displacement (mm)
40
60
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Finite Element Wall Analysis
4’ x 4’ wall, Adhesive + screws
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Unit Racking Load (kN/m)
10
5
0
-5
Experiment
-10
10
5
0
F.E. Model
(Monotonic)
F.E. Model (Cyclic)
-5
-10
-15
-15
-5
-3
-1
1
3
-5
5
-3
-1
1
Drift (%)
Drift (%)
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Unit Racking Load (kN/m)
Unit Racking Load (kN/m)
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Cyclic
Skeleton
Curves
10
5
0
-5
Experiment
F.E. Analysis
-10
-15
-5
-3
-1
1
Drift (%)
3
5
3
5
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Current and Future Work
Larger wall and room assembly tests to
investigate the effect of:
•
wall-diaphragm interfaces
• intersecting wall joints
• window and door openings
• anchorages and holdown variations
• bi-directional loading
The results from these tests will inform a fullscale building shake table test performed at the
University of California, San Diego
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Current and Future Work
Computational simulations of:
• sheathing-to-framing fasteners, hold
downs, and panel joints
• wall and wall assemblies
• full building systems
SDR > 0.2%
Create a new design methodology that
considers limit states of (a) collapse safety
and (b) damage control. Consider:
• life cycle costs, including savings from
earthquake insurance
• potential deterioration caused by
moisture, temperature fluctuation, aging,
etc.
Porter., K. et al. (2011). “The ShakeOut Scenario: A hypothetical Mw7.8 earthquake on the southern
San Andreas Fault.” Earthquake Spectra, Vol. 27, No. 2, pp. 239-261.
T = 0.2 s.
R/ Ω = 2.17
T = 0.15 s.
R/ Ω = 1
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Acknowledgements
• This research is funded by the National Science Foundation under a grant
from the Network for Earthquake Engineering Simulation (CMMI –
1135029).
• Additional support for testing was provided by the John A. Blume
Earthquake Engineering Center at Stanford University.
• Input and guidance from an advisory committee (Greg Luth, David Mar,
Kelly Cobeen, Reynaud Serrette, John Osteraas, Rene Vignos, Geoff
Bomba, and Ali Roufegarinejad) has been critical in the development of
testing plans.
• Support and encouragement from Ben Schmid, developer of the MAXISYSTEM and the enhanced fasteners tested is thankfully acknowledged.