Transcript Final Project Update: Investigation of Fastening of Wood Structural Panels for Opening Protection Forrest J.

Final Project Update:
Investigation of Fastening of Wood Structural
Panels for Opening Protection
Forrest J. Masters, PhD, PE, Associate Prof. of Civil Engineering
Kurt R. Gurley, PhD, Associate Prof. of Civil Engineering
Engineering School for Sustainable Infrastructure & Environment
SLIDE
1
Summary of Issue
• The International Hurricane Protection Association asked the Commission to
investigate the wind resistance requirements for wood panel shutters, citing
concerns about
– Limited availability in Florida to find fasteners that satisfy requirements for embedment
and permanent installation
– Guidance for large openings, such as sliding glass doors
– Inadequate resistance to catenary forces caused by out-of-plane deflection of the
structural wood panel
– Inadequate/missing edge distance requirements
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2
Relevant Sections of the Code
•
•
•
•
1209.1.2, Exception 1,
Florida Building Code
2010: Building
Table 1609.1.2, Florida
Building Code 2010:
Building
R301.2.1.2, Exception,
Florida Building Code
2010: Residential
Table R301.2.1.2,
Florida Building Code
2010: Residential
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3
Permanent
Anchorage
Takeaway #1
Calculating the wind loads for labeling and product approval of impact
resistant coverings is overcomplicated and results in a proof load that is
90% of the ASCE 7-10 C&C value
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4
ASD  LRFD
Vasd
LRFD= Vult 0.6
Vasd
Vult =
0.6
LRFD  ASD
Unfactored  Factored
ASD  LRFD
LRFD
LRFD  ASD
Unfactored  Factored
ASD  LRFD
LRFD
LRFD  ASD
Unfactored  Factored
ASD  LRFD
LRFD
LRFD  ASD
Unfactored  Factored
10% reduction. These values should be
the same to achieve consistency between
ASCE 7-10 and the standardized tests
LRFD
LRFD  ASD
BETTER APPROACH: Only use the equations you need
ASCE 7-10 C&C Part 2 is fine, too
BEST APPROACH: Provide a table lookup and explicitly
define the termonology in the standardized test methods
Takeaway #2
The wind-borne debris protection fastening schedule for wood
structural panels has some issues, such as allowing for an 8 ft
unsupported span of 7/16 OSB in extreme winds
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16
IHPA sponsored test at ATI in 2011
Failed at 25 psf
SLIDE
IHPA sponsored test at ATI in 2011
SLIDE
IHPA sponsored test at ATI in 2011
8 ft
No fastening on panel edge
Fastened
at ends
Fastened
at ends
No fastening on panel edge
SLIDE
1 in edge distance
1 in end distance
“Tear-Out”
SLIDE
Takeaway #3
Structural wood panels are a good choice for a low-cost storm
shutters outside of the HVHZ if the fastening schedule is adequate
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21
Technical Approach
•
Find a one-size-fits-all, simple-to-build, low-cost approach for for a ‘worst case’ building:
–
–
–
•
Mean roof height <= 45 ft
Located in Exposure D
Vult = 180 mph or less
Reinhold (2003) found that 7/16 OSB panel (more or less) meets impact resistance for
regions outside the high velocity hurricane zone
– Shutters can resist ASTM E1996 Missile C, i.e. a 4.5-pound 2x4 traveling at 27 mph
•
Thus impact resistance was not revisited
SLIDE
22
Technical Approach
•
Adapted prescriptive design in Table 1609.1.2. Key aspects of design
–
–
–
–
–
–
–
•
Kept minimum thickness requirement (7/16) for OSB panel
Moved fasteners from panel ends (short side) to panel edges (long sides); Effect = 8 ft  ~4 ft span
Chose a single fastener configuration (hanger bolts appear to be the best option)
Increased the fastener-to-edge distance from 1 in to 2 in to prevent panel tear out
Required slightly oversized holes to reduce the catenary force (and make it easy to hang the panel)
Required 3 in wall overlap to limit inward deflection
Use large (1 in) washers or washered wingnuts to prevent pull-through
Other fastening systems are allowed but the shutter system must be certified for use in FL
SLIDE
23
Many Fastener Options for Wood Substrates
Used in our tests
¼-20 Washered
Wingnut
1-1/8 in Flange
¼-20 Washered
Wingnut
7/8 in Flange
¼ X 1 in
Fender
Washer
¼-20
Hexnut
¼ X 5/8 in
Washer
¼-20
Hexnut
14 X 3-7/16
PanelMate
Plus 305SS
14 X 3-7/16
PanelMate
Plus 305SS
¼-20 X 4 in
Hanger Bolt
18-8 Stainless
1/4 X 3-7/16
PanelMate
Plus 305SS
1x3
TEST CASE 1
2.00 in embedment
0.00 in exterior finish
2x4
1x3
TEST CASE 2
1.25 in embedment
0.75 in exterior finish
2x4
Counterbore hole
A Low
Cost
Option
Technical Approach
•
Later we will discuss the importance of catenary loading caused by panel deflection
•
Lateral forces + withdrawal forces cause combined loading on the fastener
•
However, we’re skeptical that the closed-form solutions produce a reasonable upper bound
•
Thus we stuck to physical testing of the design to evaluate if it works
•
Tested light-frame wood constructions, CBS tests to come
SLIDE
30
Dwyer
Pressure
Gauge
Stud to prevent panel
making contact with laser
system
Interior
Panel
Face
Data Acquisition System
Laser Displacement
Measurement System
FULL PANEL TESTING CONFIGURATION
Pressure
Chamber
Control
System
Blower
Valve
Air
Pressure
Loading
Actuator
FULL PANEL TESTING CONFIGURATION
How a pressure loading actuator works
This half makes
an air circuit with
the fan
Port
Connects
to
Pressure
Chamber
The motor spins a
slotted round disk
between the halves
This half drives
has three ports
that connect to
the pressure
chamber, exhaust
and intake
Designed by Cambridge Consultants and the University of Western Ontario
ASTM E330 Proc. A was
applied for evaluating
resistance to uniform
static pressure
60 s
10 s
(+) Proof Load
(+) Test Load
It is similar to TAS 20294 but applies
• 2/3 of the “proof”
load first, i.e. the
“test” laod
• loads in sequence
(positive then
negative)
(-) Test Load
(-) Proof Load
ASTM E330 Proc. A was
applied for evaluating
resistance to uniform
static pressure
Positive pressure: polyethylene
plastic sheeting installed on the
panel side in the chamber
Maximum rest
= 5 minutes
Not enough time to
reconfigure setup
Negative pressure: polyethylene
plastic sheeting installed on the
panel side in the free atmosphere
TAS 202-94…
Does anybody
actually follow the
instructions?
We think not…?
50% of the test load, then
50% of the reverse test load
100% of the test load, then
100% of the reverse test load
FOR THE TEST LABS AND PRODUCT MANUFATURERS OUT THERE…
NOW YOU CAN RUN +/- WITHOUT CHANGING THE CONFIGURATION.
DOUBLE BAG AND FACE THE VALVES AWAY FROM THE PANEL
FOR THE TEST LABS AND PRODUCT MANUFATURERS OUT THERE…
NOW YOU CAN RUN +/- WITHOUT CHANGING THE CONFIGURATION.
DOUBLE BAG AND FACE THE VALVES AWAY FROM THE PANEL
ASTM E330
Case 1
Positive Test
Polyethylene
plastic sheeting
installed on the
panel side in
the chamber
~75 mm in pos. load
ASTM E330
Case 1
Negative Test
Polyethylene
plastic sheeting
installed on the
panel side in
the free
atmosphere
~65-70 mm in neg. load
ASTM E330
Case 1
Both Loads
Polyethylene
plastic sheeting
+ check valves
installed on
both sides of
panel
~75 mm (identical)
60-65 mm (within 10%)
Results for Case 2
(which look pretty much the same as Case 1)
SLIDE
42
ASTM E330
Case 2
Both Loads
Polyethylene
plastic sheeting
installed on
both sides of
panel
~75 mm
60-65 mm (within 10%)
For the cyclic tests, the better option was to install the
polyethylene plastic sheeting on one side
(or use a larger blower)
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44
ASTM E1996
Case 1
Positive
Cycles
ASTM E1996
Case 1
Negative
Cycles
ASTM E1996
Case 2
Positive
Cycles
ASTM E1996
Case 2
Negative
Cycles
Takeaway #4
Predicting the catenary forces is not trivial
given the current knowledge base
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49
Catenary Forces
• Many theories for how OSB panels behave, little supporting data
• Some opinions
– One extreme: design for the worst case (which blows up the numbers)
– The other: pressure equalization limits the midspan deflection and thus the catenary force
• Our take is that the lateral stiffness at the supports has a large influence on the
panel deflection and the catenary force
• Lateral stiffness is dependent of a combination of factors, including:
– Flexural bending of the fasteners or other yield modes (crushing, rotating, hinging),
– Slippage caused by oversized holes (3/8 hole = ¼ diameter = 1/8 inch of unrestrained movement)
• However no reference values for 7/16 OSB
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50
Specimen
Pressure
Chamber
Laser Displacement
Measurement System
Air
Polyethylene
Plastic Sheeting
•
•
Gasket for
pressure
chamber
Installed on
exterior for (+)
pressure tests
Installed on
interior for (-)
pressure tests
Service
Port to
Pressure
Loading
Actuator
STRIP PANEL TESTING CONFIGURATION
Polyethylene
Plastic Sheeting
•
•
Installed on
exterior for (+)
pressure tests
Installed on
interior for (-)
pressure tests
A
B
A = 51 mm (2 in)
B = 25 mm (1 in)
Rough
Opening
7/16 OSB
Strip Dimensions
• 406 mm (16 in) width
• 1219 mm (48 in) length
• 1092 mm (43) in unsupported
distance between R.O.
Hardware
•
1/4 X 3-7/16 PanelMate
Plus 305SS
•
¼ X 1 in fender washer
•
¼-20 hexnut
•
1.25 in embedment
NEGATIVE
LOAD
> 126 psf
✔ OK
5
Experimental test
FE results (laterally rigid)
FE results (high lateral stiffness)
FE results (medium lateral stiffness)
FE results (low lateral stiffness)
4.5
4
Deflection (in)
3.5
3
2.5
2
1.5
1
0.5
0
0
10
20
30
40
50
60
70
80
Pressure (psf)
90
100
110
120
130
140
2400
FE Results (laterally rigid)
FE Results (high lateral stiffness)
FE Results (medium lateral stiffness)
FE Results (low lateral stiffness)
2100
Lateral force (lbf)
1800
1500
1200
900
600
300
0
0
10
20
30
40
50
60
70
80
Pressure (psf)
90
100
110
120
130
140
A
B
A = 51 mm (2 in)
B = 25 mm (1 in)
Rough
Opening
7/16 OSB
Strip Dimensions
• 406 mm (16 in) width
• 1219 mm (48 in) length
• 1092 mm (43) in unsupported
distance between R.O.
Hardware
•
14 X 3-7/16 PanelMate
Plus 305SS
•
¼ X 1 in fender washer
•
¼-20 hexnut
•
1.25 in embedment
POSITIVE
LOAD
> 94 psf
✔ OK
4
Experimental test
FE results (laterally rigid)
FE results (high lateral stiffness)
FE results (medium lateral stiffness)
FE results (low lateral stiffness)
3.6
3.2
Deflection (in)
2.8
2.4
2
1.6
1.2
0.8
0.4
0
0
5
10
15 20
25
30
35
40 45 50 55
Pressure (psf)
60
65
70
75
80
85
90
2400
FE Results (laterally rigid)
FE Results (high lateral stiffness)
FE Results (medium lateral stiffness)
FE Results (low lateral stiffness)
2100
Lateral force (lbf)
1800
1500
1200
900
600
300
0
0
10
20
30
40
50
60
70
80
Pressure (psf)
90
100
110
120
130
140
Takeaway #5
Designers need closed-form solutions to calculate catenary loads
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58
Applied Force
7/16 OSB
¼ Anchor Bolt
•
As the lateral stiffness approaches infinity, the closed-form solutions
predict ‘proof’ load forces of
•
•
Universal Testing Machine
•
2000+ lbs for a double cantilevered beam exhibiting elastic,
geometrically non-linear behavior
2800+ lbs for a cable
We believe the actual deflection is on the order of a few hundred
pounds (not verified experimentally)
Takeaways #6 and #7
We need to study other combinations of hardware and wall types to
see if the one-size-fits-all approach works
We need to develop recommendations for larger openings
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60
Where the One-Size-Fits-All Approach May Not Work
• Study (so far) evaluated options for light-frame wood construction
• CMU wall system tests planned during remainder of contract
• Did not consider brick veneer (need 7 3/8 in bolts)
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SLIDE
Solid
PLANNED TESTING: Tomorrow -> June 30
SLIDE
¼-inch Anchor Bolts
for Masonry Substrate
¼-20
Machine
Screw
¼-x1 in
Fender
Washer
¼-20 Hexnut
¼-20
Washered
Wingnut
7/8 in Flange
¼-x1 in
Fender
Washer
¼-20 X 1 in
Sidewalk Bolt
¼-20 Machine
Screw Anchor
¼ x 1-3/4 in
Female
PanelMate
14 X 2-1/4
PanelMate Pro
¼ X 2-1/4
Tapcon SG
Where the One-Size-Fits-All Approach May Not Work
• No options for large openings (e.g., 60-68 sliders, field mulled windows)
• Propose to continue project to develop recommendations for these cases and
possibly revisit impact resistance
• Starting point = APA T460 Hurricane Shutter Design Considerations for Florida
– Incorporates stiffeners and provides good examples of connection details
– Addresses how to construct shutters for spans > 8 ft
SLIDE
65
Summary of Takeaway Points
1.
Calculating the wind loads for labeling and product approval of impact resistant
coverings is overcomplicated and results in a proof load that is 90% of the ASCE 710 C&C value
1.
The wind-borne debris protection fastening schedule for wood structural panels
has some issues, such as allowing for an 8 ft unsupported span of 7/16 OSB in
extreme winds  Refer to Appendix B in Final Report for recommended code
changes
2.
Structural wood panels are a good choice for a low-cost storm
shutters outside of the HVHZ if the fastening schedule is adequate
SLIDE
67
Summary of Takeaway Points
4.
Predicting the catenary forces is not trivial given the current knowledge base
5.
Designers need closed-form solutions to calculate catenary loads
6.
We need to study other combinations of hardware and wall types to see if the
one-size-fits-all approach works
7.
We need to develop recommendations for larger openings
SLIDE
68
Thank you to the
stakeholder oversight team!
All Points Screw, Bolt & Specialty Co.
American Wood Council (AWC)
APA – The Engineered Wood Association
JBD Code Services
International Hurricane Protection Association (IHPA)
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