HomeMy WebLinkAboutB04-0252 review of manufacturers snow bracket submittalLetter of Transmittal
Date: April 29, 2010
To: Martin Haeberle
Chief Building Official
Town of Vail
From: Tim Losa, Zehren and Associates, Inc.
C/o Mark Norris, Vail Plaza Hotel
Re: Vail Plaza Hotel- Certificate of Occupancy
Review of Manufacturer's Snow Bracket Submittal
Attachments:
JD�
You are receiving 3 copies of:
• Zehren letter "Review of Manufacturers Snow Bracket Submittal ", dated April
29, 2010
• CRK Engineers, Inc. correspondence, dated April 15, 2010
• Tra -Mage correspondence, dated June 12, 2007
• Tra -Mage Drawings SRP -01, SRP 01A and SRP -02, dated 3/03/2010
• Tra -Mage Bracket "A" and "H" Product Data Sheets
• Tra -Mage Bracket testing Reports
Z E H R E N
AND ASSOCIATES, INC.
April 29, 2010
Mr. Mark Norris
Director of Construction
Timbers Resorts
201 Main Street, Ste 202
Carbondale, CO 81623
Via: Electronic Mail mnorris(a),timbersresorts.com
Mr. Martin Haeberle
Town of Vail
Chief Building Official
75 South Frontage Road
Vail, CO 81657
Re: Vail Plaza Hotel — Certificate of Occupancy
Review of Manufacturer's Snow Bracket Submittal
Mark/Martin:
As specifically requested by the Town of Vail in our meeting yesterday, I have reviewed the
TRA -Mage submittal in connection with the requirements for construction for the Vail Plaza
Hotel Project as set forth in the Contract, (Building Permit), Documents and particularly with
regard to Specification Section 07322, "Concrete Roof Tiles ". The reviewed "Submittal"
included:
1. CRK Engineers, Inc. correspondence dated April 15, 2010;
2. TRA -MAGE correspondence dated 6/12/07;
3. TRA -Mage Drawings SRP -0 1, SRP -0IA, and SRP -02 dated 3/3/10 indicating minimum
bracket spacing;
4. TRA -MAGE- Bracket "A" and "H" Product Data Sheets; and
5. TRA -Mage Bracket Testing Reports.
I have reviewed the Submittal for the limited purpose of checking for conformance with
information given and the design concept expressed in the Contract Documents. In addition, the
Submittal further requested a review of certain stated snow loads from the Architect and /or
Engineer of Record.
My review confirms that Submittal complies with the design concept expressed in the Contract
Documents and the Town of Vail's adopted amendments to Section 1608.2 of the 2009
International Building Code as it relates to snow loads. In my opinion, the snow brackets, if
properly coordinated with other portions of the Work and installed in accordance with the
manufacturer's minimum requirements, should comply with the requirements for construction as
indicated in the Contract Documents.
Page 1 of 2
Z:\2004 \041590.19 \I. Project Administration \05. Owner Correspondence \Mark Norris ROOfiMN 100429 Bracket Review TL.doc
Z E H R E N
AND ASSOCIATES. INC.
Review of the submittal was not conducted for the purpose of determining the accuracy and
completeness of other details such as dimensions and quantities, for substantiating instructions,
means, methods, techniques, sequences and procedures of installation or for coordinating the
submittal with other portions of the Work under the Contract; all of which remain the
responsibility of the Contractor. Our review of the submittal does not relieve the Contractor of the
obligations to provide Work that conforms to the requirements of the Contract Documents. Work
not conforming to these requirements, including substitutions not properly approved and
authorized, may be considered defective. Our review shall not constitute approval of any safety
precautions. Our review of these specific items shall not indicate approval of an assembly of
which the item is a component.
It should be noted that the submittal, in the interest of expediting the construction processes, was
forwarded directly from the manufacturer to Zehren and Associates, Inc. without prior approval
from the Contractor. It is our understanding that the Owner will secure the necessary approvals
from the Contractor, as required by the Contract Documents, prior to installation of the brackets.
Sincerely,
Timothy R. Losa, A.I.A.
Principal — Architect of Record
Zehren & Associates, Inc.
Page 2 of 2
ZA2004 \041590.191. Project Administration \05. Owner Correspondence \Mark Norris Roof\MN 100429 Bracket Review TL.doc
April 15, 2010
Mr. Ron Grover
TRA -Mage Roof Accessory Systems
1657 South 580 East
American Fork, UT 84003
Re: Vail Plaza Hotel — Roofing Plan 1
Vail Plaza Hotel — Roofing Plan 2
Snow Bracket Installation — Vail, Colorado
CKR Job No.: 10135
Dear Ron:
This letter addresses the application of two types of snow brackets for the roofs in the referenced
project. Attached to this letter are documents that you sent to us regarding the application of
your patented snow brackets to these roofs. You have sent the following items to us and we
present the following bracket design assumptions.
1. - TRA -Mage disclaimer regarding the fact that the snow brackets are designed with the
strength to retain the snow, but that the snow itself may pass around or over the bracket
system. Thus, some snow may penetrate the brackets without damaging the brackets
themselves.
2. Layout drawings you produced labeled SRP -01, SRP -OIA and SRP -02 showing the
different areas of bracket placement and spacing. You have stated that you produced
these drawings using the information received from the contractor. You have stated on
the drawing a uniform ground snow load of 100 psf (pounds per square foot.)
3. - "BRA -Mage schematic bracket drawing A.
4. TRA -Mage schematic bracket drawing H.
5. TRA -Mage schematic H bracket installation drawing.
6. PSI report of testing values for the H bracket.
7. TRA -Mage testing data for the A bracket.
1295 N. State Street, Orem, Utah 84057
SLC 801- 984 -1301, Orem 801- 222 -0922, fax 801- 222 -0902
TRA -Mage
April 15, 2010
Page 2
Notes:
We have not received any information directly from the engineer of record regarding the
stated ground snow load or the roof snow load, including any balanced, unbalanced or
drifted snow loading. We have calculated allowable snow loads based on your supplied
bracket spacings, coinciding with TRA drawings.
We advise TRA -Mage to request that the engineer of record review these snow loadings
for compliance with his design. The engineer of record should approve these loadings or
should supply a complete roof snow load diagram with all loads clearly shown. Bracket
spacings may then be adjusted as necessary based on those received loads.
CKR Engineers accepts no liability for the roof snow loadings and presents these
estimated snow loads for review by the engineer of record and his final approval.
TILE APPLICATION BRACKETS — A
You have sent to us TRA -Mage layout drawings for the attachment of the A bracket on the two
building roofs. We have included calculations for the maximum snow loads retained by the
snow brackets. Please refer to the drawings SRP -01 through SRP -02 for correlation of bracket
spacings and roof slopes. The summary of this information follows.
Spacing Width
Spacing Height
Pitch/12
Allowable Snow Load:
Inches
Feet
PSF
12
3.5
7
100
.5
3.5
7
200
12
3.5
16
75
.5
3.5
16
150
In accordance with these criteria, the following design notes should be noted and followed.
BRACKET NOTES
Bracket Testing
1. CKR Engineers has not designed the actual snow bracket but has evaluated the testing
data for the designated bracket for shear capacities and failure modes. These tests were
performed for TRA. CKR did not design or perform the tests.
2. The testing appears to have been completed in accordance with generally accepted
materials engineering and testing principles and practices. No other warranty, either
expressed or implied, is made. CKR Engineers is evaluating the information supplied by
TRA. TRA takes responsibility for the testing data.
TRA -Mage
April 15, 2010
Page 3
3. The bracket testing specimens were fastened to the substrate as detailed in the attached
documents.
4. The test data supplied by TRA indicates the failure modes of the brackets. The engineer
of record and others are responsible for the strength and resistance values for the
structural elements supporting the brackets.
5. The test data indicates the failure mode for these brackets was an eventual yielding of the
resisting end piece attached to the roof. It has been our experience that the value of this
failure is below the strength of the triangular portion of the bracket.
6. The shear load on the bracket can be correlated back to a roof snow load by the formula:
Shear Load = (FL * (W/12) * L * Sin (Theta)) * SF
Where: FL = snow load
W = panel width in inches
L = panel length in feet
Theta = Roof pitch = arctan (X/12)
X = vertical rise in roof surface over 12 inches
SF = appropriate factor of safety
7. In evaluating the test data presented by TRA -Mage, it is our opinion that a factor of
safety of 2 is appropriate for these bracket loads. The resulting design value used in the
calculations is 213 lb. for an individual bracket. Note that the snow loading is a projected
loading that may be reduced by the ratio of that projected length divided by the actual
length between the brackets.
Tile Roof
The engineer of record is responsible for the properly engineered and attached supporting
structural elements. Care should be taken to attach the battens to the underlying structure to
support the tiles and resist the applied bracket loadings.
SNOW BRACKET "H" — SOLDERED BRACKET TO METAL ROOF
Attached to this letter are the layout drawings from TRA -Mage regarding the placement of the
"H" connectors. At your request, we have reviewed the capacity of the soldered "H" bracket
manufactured by TRA Mage as reported by PSI on October 18, 2006. We were presented with
these test results and they are attached. CKR Engineers has not designed the actual snow bracket
but has evaluated the testing data for the designated bracket for shear capacities and failure
modes.
These tests were performed by TRA. CKR did not design or perform the tests. According to
TRA -Mage, the testing was completed in accordance with generally accepted materials
engineering and testing principles and practices. No other warranty, either expressed or implied,
is made. CKR Engineers is evaluating the information supplied by TRA. TRA takes
responsibility for the testing data.
TRA -Mage
April 15, 2010
Page 4
We have reviewed these testing results as they relate to the application of the bracket for this
project. You have stated an average failure load on the bracket of 680 lb. A factor of safety of
1.7 results in a bracket strength of 400 lb. The maximum allowable snow load resisted by each
bracket is as follows.
Spacing Width
Spacing Height
Pitch/12
Allowable Snow Load:
Inches
Feet
PSF
24
4
7
100
12
4
7
200
29
3
16
71
14.5
3
16
142
29.75
6
3
100
15
6
3
200
The engineer of record should review these loadings on these brackets for compliance to the
project specifications and his calculations.
CKR accepts no liability for the design loads, which should be approved by the engineer of
record through TRA, nor do we accept liability for the application of the bracket to the roof.
The shear load on the bracket can be correlated back to a roof snow load by the formula:
Shear Load = (FL * (W /12) * L * Sin (Theta)) * SF
Where: FL = snow load
W = panel width in inches
L = panel length in feet
Theta = Roof pitch = arctan (X/12)
X = vertical rise in roof surface over 12 inches
SF = appropriate factor of safety (We suggest 1.7)
Please call if you have further questions. We appreciate the opportunity to be of service to you.
Sincerely,
A��
Steve 0i Cosper, P.E.
Enclosures
MAIGE
657 South 580 East
%mehcan Fork, UT 84003
-800- 606 -8980
801) 756 -8666 Phone
801) 756 -7891 Fax
Tuesday, June 12, 2007
To Whom It May Concern:
The snow retention system TRA Snow Brackets is designing is not guaranteed to hold
all the snow on the roof. In my opinion, no snow retention system can hold all the snow;
small pieces of snow can always come through because of wind, sun, and other various
conditions. TRA Snow Brackets designs systems to meet certain conditions, based on
information provided by the structural plans, architect, and structural engineer, etc. We are
not responsible for any damages resulting in faulty information provided by the purchaser or
the purchaser's agents. TRA's snow brackets are designed to keep large sheets of snow from
sliding off the roof and damaging people, property, gutters, etc. We warranty the snow
brackets themselves from damage and send replacements if necessary along with a free
design for a new snow retention system, but we do not take upon ourselves any liability for
damage to people or property due to falling or sliding snow. Also, the snow retention system
does not eliminate the potential problems of ice dams and icicles, these potential problems
are resolved through proper insulation and in some cases heated gutters, downspouts, eaves,
valleys, etc. All this said, we do feel the likelihood of having a sliding or falling snow
related accident is very much reduced by using a snow retention system.
We have put as much thought and engineering as we feel to be reasonably possible to
ensure a good system. We hope that you will be pleased with the designed snow retention
system, and that you would be happy to do business with us again.
Sincerely,
Jacob Anderson
TRA -Mage Roof Accessory Systems
Utah/Idaho Sales Manager
PH: (801)756 -8666 FAX: (801)756 -7891
CELL: (801)380 -4150 E- Mail:Jacob @tra- mage.com
rww.tra- mage.com
ifo@tra- mage.com
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VAIL PLAZA HOTEL
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VAIL PLAZA HOTEL
COLORADO
SNOW RETENTION PART SCHEDULE
PARTIDESC OTY
HSOLDER ON (COPPER) 142
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SRP -01A
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UNDERSIDE VEw
INSTALLATION:
COPPER SURFACL MUST SE CLEANED TO
REMOVE ALL ORGANICS AND OXIDATION.
SN BRACKET IS SOLDERED TO
ROOFING SURFACE WITH FLUX AS
SNOW SRACKET.WSOLDERED NEEDED BRACKET CAN BE ORDERED
WITH SOLDER PRE^APPLIED TO BOTTOM
COPPER STANDING SEAM SURFACE.
H BRACKET DETAIL
I NO SCALE
SNOW BRACKET IS INSTALLED ON THE
TOP 61RtfACE OF THE TILE WfTH TFE
TRIANGULAR END OF THE BRACKET OVER
SNOW SRACKET'A' THE HEADIAP OF RTE TILE AND THE
SPIKE NSTALLEO Nf0 1 X 2 BATTEN.
S TILE ROOF
A BRACKET DETAIL
2 NO SCALE
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1657 South 680 EW
AmencaR Fork UT 84003
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VAIL PLAZA HOTEL
COLORADO
NO SCALE
SRP -02
6N04T RETE MA DETAI
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ROO ACCESSORY SYSTEMS
PRODUCT DATA SHEET
SNOW BRACKET A
DESCRIPTION
• Designed for use with concrete tiles which are installed using
horizontal battens.
• No fasteners required.
Powder coated to match roofing material color
• Overall dimensions: 18 -1/2 "L X 1- 3/16 "W X 4 -5/8" H
MATERIALS
• 16 ga. Electrogalvanized Steel
• 48 oz. Copper
• Aluminum (.063" thick)
• Stainless Steel
• Cor -Ten®
COLORSIFINISHES
• Electroga Ivan ized Steel
Mill finish Copper
Mill finish Aluminum
• Mill finish Stainless Steel
• Powder coating available in RAL Standard colors
• Visit www.tra - mage.com to see color chart
NOTE: Due to specific job conditions. TRA -Mage will only warranty a snow
retention system/layout that has been deisgned by TRA -Mage.
Is
c
FOR NEW CONSTRUCTION
USED ON: COLUMBIA, EAGLE, HANSON,
MONIER, LIFETILE, UNICRETE WESTILE
& OTHER SIMILAR TILES
Bracket is installed with triangular end of bracket at eave end of
roofing material and upper end under course above.
BRACKET INSTALLATION
DO NOT SCALE
BRACKET DIMENSIONS
00 NOT SCALE
TRA -MAGE, Inc.
1657 South 580 East
American Fork, UT 84003
FOR MORE INFORMATION CALL: (800) 606 -8980
VISIT US ON THE WEB: www.tra - mage.com
Jw -D4 -2010
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2 SNOW BRACKET 'H' DETAILS
NO SCALE
UNDERSIDE VIEW
SNOW BRACKET'H' SOLDERED
COPPER STANDING SEAM
INSTALLATION:
COPPER SURFACE MUST BE CLEANED TO
REMOVE ALL ORGANICS AND OXIDATION.
SNOW BRACKET IS SOLDERED TO
ROOFING SURFACE WITH FLUX AS
NEEDED. BRACKET CAN BE ORDERED
WITH SOLDER PRE - APPLIED TO BOTTOM
SURFACE,
3 SNOW BRACKET 'H' ROOF DETAILS
NO SCALE
;.To bf ulld On
Engineering d Consulting o Testing
REPORT OF LABORATORY TESTING
CLIENT: ANDERSON & ASSOCIATES PROJECT: laboratory 1'esting of
P.O. BOX 261 Proprietary Snow Brackets
PLEASANT GROVE UT 84062
DATE: October 18, 2006 OUR REPORT NO.: 706- 40005 -018
SUBJECT; SNOW BRACKET PANEL TESTING
BACKGROUND:
PSI performed laboratory testing under the direct supervision of Kevin Ellers of TRA -Mage. Six (6) "H- Brackets"
were tested to ultimate load (lbs-f), as determined by TRA. The copper H- bracket had been previously attached to
a lead- coated copper roofing panel by soldering and the entire assembly was secured to a wooden board with
four (4) screws. A continuous load was applied by PSI to the H- bracket assembly until TRA determined that failure
had occurred. The following is a summary of the testing.
LABORATORY TEST RESULTS:
Bracket #1
700 lbs
Horizontal brace begins to bend
800 lbs
Diagonal brace begins to deform
845 lbs
Diagonal brace fails
Bracket 42
380 lbs
Horizontal brace begins to bend
640 lbs
Diagonal brace begins to deform
753 lbs
Diagonal brace fails
Bracket #3
430 lbs
Horizontal brace begins to bend
640 lbs
Diagonal brace begins to deform
661 lbs
Diagonal brace fails
Bracket #4
340 lbs
Horizontal brace begins to bend
680 lbs
Diagonal brace begins to deform
711 lbs
Diagonal brace fails
Bracket #5
280 lbs
Horizontal brace begins to bend
510 lbs
Diagonal brace begins to deform
578 lbs
Diagonal brace fails
Bracket #6
270 lbs
Horizontal brace begins to bend
520 lbs
Diagonal brace begins to deform
555 lbs
Diagonal brace fails
LAB TECHNICIAN:
Kellie Queen
IMESE RESUL)SAFPI'YL)M Y TO 11IFSPECIFICSAMPLES IESIEL REIKJi1 IS hVV1 VC)f 6L
RF.F`ROrXXFn FXCFPI'IN FUII Wi(HOUI'MZI I - !EN PERIAISSNNJ BY PROFFSSIONk S[RVu
INDUSTRIES, INC
Respectf Ily submitted; -,
PRO, E SIONAL SERVICE INDUSTRIES, INC.
jL
.1
Grogory N. AQdersZx
Construction 15*vicps 7epartment Manager
Prore'sinrTal ervice industries, Inc. 2779.tiouth 600 West Sall I -ake Cilr. 1 fair 811 IS Phone 801 -48 -1 88 17 Fax 510[ 587•x.512
CONCRETE TILE
BRACKET
TESTING
Snow and Ice slide prevention devices
for all types of roofs
P.O. Box 682, American Fork, UT 84003
(801) 756 -8666, fax (801) 756 -7891
STATIC FIELD TESTING OF TRA SNOW BRACKETS
conducted for
Tile Roof Accessories, Inc.
P.O. Box 682
American Fork, UT 84003
(801)756 -8666 Tel.
(801)756 -7891 Fax.
X41k- zlz a-46&��
illardson, E 'neering Assistant
David Jens roject Engineer
David Sorensen, Director RPRC
Rapid Product Realization Center
Brigham Young University
Provo, Utah 84602
April 14, 1995
INTRODUCTION
A strength verification test of the Tile Roof Accessories (TRA) Snow Bracket was
performed in the field according to specifications independently recommended by Brigham Young
University. In addition, Brigham Young University supervised and assisted in the performance of
this test. A field test was necessary to resolve questions about how accurately initial laboratory
tests had simulated the actual response of an installed bracket.
The objective of this test was to determine the TRA Bracket's maximum capacity when
subject to a uniform snow load on a file roof. Towards this end, an existing the roof was chosen
for the test. The test roof was a black shake Monier concrete tile, simple pitched roof on a small
one story structure which was easily accessible from all four sides. Each half of the roof was 8' by
6', yielding a total of 48 square feet of roof area per side. The roof had a 12/12 pitch (45' slope).
A sketch of the test roof is shown below in Figure 1 (also see photographs in Appendix).
A testing scenario was devised to simulate one of the potentially worst cases of snow
loading on the brackets: packed snow or ice which is free to slide down the roof on a thin layer
of water, with little or no frictional resistance. The testing scenario to simulate this loading
Figure 1: Test Roof Sketch
involved covering the test section of roof with a sheet of plastic, placing blocks of ice on the
plastic, and finally adding additional weight on top of the ice via bags of gravel (the ice on the
plastic representing the frictionless surface). A wood beam was used to support the ice and
gravel mass between two snow brackets. Figure 2 below shows a sketch of the testing setup. It
is assumed that this setup resulted in near zero friction between the mass and the roof; allowing
the down -roof component of the weight vector to be interpreted as direct load on the beam and
the snow bracket. The weight was increased slowly to the desired load of 1200 lb. This 1200 -1b.
static load was pre - determined to be large enough to simulate very heavy snow loads including a
factor of safety. Also, this load was limited by what was reasonable and safe for the performance
of the test.
Aets
Figure 2: Test Setup
,. .
The test was performed on Tuesday, March 28, 1995 between 12:30 p.m. and 3:30 p.m.
The weather conditions were overcast with high temperatures between 40'F and 45 ° F and there
was a slight breeze from the north. The six-step procedure followed to field test the brackets is
described in the following paragraph.
1. The brackets were mounted according to manufacturer's specifications on the last row of
tiles at the bottom of the roof separated by a distance of 3 feet.
2. A sheet of plastic (006 in. thick) was then draped over the brackets and up over the ridge
of the roof.
3. A four foot wooden beam (2" by 4 ") was placed on top of the plastic spanning the
distance between the two brackets. The beam was not allowed to contact the roof
directly.
4. Twenty blocks of ice were stacked against the wooden beam and on top of the plastic in
four columns, Each block of ice measured approximately 6" x 6" x 9" and weighted about
11 lb.
5. Another wooden beam (2" by 10 ") was placed between the second and third rows of ice to
provide a bearing area on the ice for the additional gravel load, Again, this beam was not
allowed to come in direct contact with the roof.
6. Additional load was applied by stacking 25 -1b. bags of gravel on top of the ice blocks,
When the supply of gravel bags ran out, other items were weighed and added to the stack
until the desired load of 1200 lb. was reached. The full 1200 lb. load was left on the roof
for about half an hour prior to concluding the test.
The load was increased to a total of 600 lb. before any notable deformation of the snow
bracket took place. At this load, the upper end of the bracket (the attachment mechanism) began
to yield and the end of the bracket moved down the roof about 3/8 in. As the load increased from
600 lb. to 1000 lb., the load path redistributed to other parts of the bracket and the down -roof
displacement stabilized at about 3/4 in. The load was increased until it reached the pre - specified
limit of 12001b. At this final load, the down -roof displacement had become about 1 -1/2 in., but
the brackets were able to sustain the full load without catastrophic failure. The mode of
deformation was a progressive straightening of the bracket's attachment mechanism. No
deformation was observed in the triangular frame on the lower end of the bracket. Additionally, it
should be noted that the load did not cause any observable damage to the concrete roofing tiles.
DISCUSSION OF RESULTS
Assuming that the friction of the melting ice on the plastic is negligible, the distributed
load of 12001b. has a down -roof component of 849 lb. This 849 lb. distributed load is applied to
the simply- supported wood beam. The snow brackets provide the support reactions for the wood
beam which are 425 lb. on each bracket. Thus, each snow bracket sustained a load of 425 lb.
without failing. Therefore the maximum capacity of an TRA Snow Bracket is 425 lb. without any
factor of safety. Alternatively, the maximum capacity of the bracket is 213 lb. with a factor of
safety equal to 2.0. Naturally, the choice of an appropriate factor of safety is up to the designer.
It should be noted that these preliminary values are somewhat limited in their general
application, since only one test was performed with only two snow brackets. Testing additional
samples would be necessary to quantify the reliability of this test data.
Assuming an allowable capacity of 213 lb. for. each snow bracket (based on a factor of
safety equal to 2), 25 brackets should be able to support a 75 lb. /ft. snow load on 100 square feet
of roof (a standard roofing square) with a 12/12 pitch. The graph in Figure 3 below extrapolates
this data to other snow loads and different roof slopes.
�40
ar
V
Z 35
0
W30
4.
0 25
m
0 20
15
=111
5
Snow LcedW
15 20 Z W 35 40 45 T 55 W 65 70 75
- -* -15ps
- -® --Mps
- --A--25ps
- *-30ps
-*-35p9
-4- 40 p9
+45 pd
50pS1
55ps1
- 0 --60psf
- -0 -66psf
- -t-70PS1
-X-75psf
0 5 10 15 20 25 30
9"a* ft per RiX&V S*M
Figure 3: Contours of Snow Load vs. Roof Slope and Number of Brackets Required
NOTE: The information on the graph in Figure 3 includes a safety factor of 2 as described in the
Discussion of Results above. It should be noted that yielding occurs at the above design load with
no safety factor as described in the Observations and Results above. Also, the test results are
based on zero friction between the snow or ice load and the concrete the roof.
It should also be noted that because the test was not able to completely fail the brackets, and the
actual ultimate capacity of the bracket could be greater than 425 lb. It is impossible to predict the
actual ultimate capacity of the brackets from the results of this test.
10 WtIMA-9 14.1e
Based on the preliminary results and discussion described above, the tentative maximum
capacity of the TRA Snow Bracket is 425 lb, (with no safety factor) when subjected to a uniform
loading on a concrete tile roof. This conclusion is based on the limited amount of available data.
Further testing on a laboratory scale is recommended to determine a more reliable
capacity. These laboratory tests should attempt to simulate actual field conditions. The tests
should be performed to failure to provide more accurate information that could be utilized in the
design process. Also, a simple modification of the snow bracket design is recommended to
prevent the tile attachment mechanism from straightening under load. This modification would
increase the load capacity of the bracket; and the additional test data would result in improved
reliability in the data and possibly a reduction in the safety factor used by the designer.
Snow Load (psf)
55
50
? ) r` 4 5
l
i J
- Yl
40
6
w
6
di
c
0
m
35
30
15 45 75 105 135 165 195 225 255 285
30 Gf 90 120 150 180 210 240 270 300
7 11
-
- -a
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- - - _ `� x: __ .l !(: :ice. ][, aCf iJ. � }.( P � ..,_. _._39[1:, -�,•. [t::_C /irG .::' � ♦tt[
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'1. „• - - - :: - ]•l t: Jt" ::]'.:C. __ _ 1- i:=::, �(::_ 5 -.- Tr - : - r)C
.. •if: Y: r:f,: lc+=.:•.1 _.: .T.: :-i Via: }:
— e-- IS psf
t — a--- 30 psf I
—& -43 psf
—x 60 psf
—)K 75 psf
— a 90 psf
---k -- 105 psf
120 psi
135 psf
--0 -150 psf
— �— 165 psf
�— 180 osf
—- 195 os f
-N 210 ps f
'_' 22
.- 5 p
20
�> : -t -240 psf
2SS psf
(. :L1: t 270 psf
:(. :�•: J' `•,+ , �; . I _-o- 285 p>f
330 PSI
tw
v 20 40 60 80 100 123
Brackets per P•oofi::q Square
TRA Snow Brackets
Width of Panel (inches)
12
Length of Panel (feet)
3.5
Roof Pitch (x/12)
7
Snow Load (Lbs per ft
100
Screw Strength (Lbs)
0
Snow Fence Strength (Lbs)
213
Number of screws needed
6
(per panel)
0
Number of fences needed
&8
(per panel)
200
A Tile Bracket - 1' -0 "H x 3' -6 "V Spacing
TRA Snow Brackets
Width of Panel (inches)
6
Length of Panel (feet)
3.5
Roof Pitch (x/12)
7
Snow Load (Lbs per ft)
200
Screw Strength (Lbs)
0
Snow Fence Strength (Lbs)
213
Number of screws needed
0
(per panel)
Number of ences needed
(per panel)
0.8
A Tile Bracket - 0' -6 "H x 3'-6 "V Spacing
TRA Snow Brackets
Width of Panel (inches)
12
Length of Panel (feet)
3.5
Roof Pitch (x/12)
16
Snow Load (Lbs per ft)
75
Screw Strength (Lbs)
0
Snow Fence Strength (Lbs)
213
Number of screws needed
6
(per panel)
0
Number of fences needed
1.0
(per panel)
150
A Tile Bracket - 1' -0 "H x 3'-6 "V Spacing
TRA Snow Brackets
Width of Panel (inches)
6
Length of Panel (feet)
15
Roof Pitch (x/12)
16
Snow Load (Lbs per )
150
Screw Strength (Lbs)
0
Snow Fence Strength (Lbs)
213
Number of screws needed
(per panel)
0
Number of fences needed
(per panel)
1.0
A Tile Bracket - 0' -6 "H x 3' -6 "V Spacing
TRA Snow Brackets
Width of Panel (inches)
24
Length of Panel (feet)
4
Roof Pitch (x/12)
7
Snow Load (Lbs per ft 2 )
100
Screw Strength (Lbs)
0
Snow Fence Strength (Lbs)
400
Number of needed
12
(per panel)
0
Number of fences needed
1.0
(per panel)
200
H Soldered Bracket - 2' -0 "H x 4'V Spacing
TRA Snow Brackets
Width of Panel (inches)
12
Length of Panel (feet)
4
Roof Pitch (x/12)
7
Snow Load (Lbs per ft)
200
Screw Strength (Lbs)
0
Snow Fence Strength (Lbs)
400
Number of screws needed
(per panel)
0
Number of fences needed
(per panel)
1.0
H Soldered Bracket - 1' -0 "H x 4'V Spacing
TRA Snow Brackets
Width of Panel (inches)
29
Length of Panel (feet)
3
Roof Pitch (x/12)
16
Snow Load (Lbs per ft)
71
Screw Strength (Lbs)
0
Snow Fence Strength (Lbs)
400
Number of screws needed
14.5
(per panel)
0
Number of fences needed
1.0
(per panel)
142
H Soldered Bracket - 2' -5 "H x TV Spacing
TRA Snow Brackets
Width of Panel (inches)
14.5
Length of Panel (feet)
3
Roof Pitch (02)
16
Snow Load (Lbs per ft)
142
Screw Strength (Lbs)
0
Snow Fence Strength (Lbs)
400
Number of screws needed
(per panel)
0
Number of fences needed
(per panel)
H Soldered Bracket - 1' -2.5 "H x 3'V Spacing
TRA Snow Brackets
Width of Panel (inches)
29.75
Length of Panel (feet)
6
Roof Pitch (x/12)
3
Snow Load (Lbs per ft)
100
Screw Strength (Lbs)
0
Snow Fence Strength (Lbs)
400
Number of screws needed
15
(per panel)
0
Number of fences needed
0.9
(per panel)
200
H Soldered Bracket - 2' -6 "H x &V Spacing
TRA Snow Brackets
Width of Panel (inches)
15
Length of Panel (feet)
6
Roof Pitch (x/12)
3
Snow Load (Lbs per ft)
200
Screw Strength (Lbs)
0
Snow Fence Strength (Lbs)
400
Number of screws needed
(per panel)
0
Number of fences needed
(per panel)
0.9
H Soldered Bracket - 1' -3 "H x 6'V Spacing
TRA Snow Brackets
Width of Panel (inches)
28.25
Length of Panel (feet)
3
Roof Pitch (x/12)
10
Snow Load (Lbs per )
90
Screw Strength (Lbs)
0
Snow Fence Strength (Lbs)
400
Number of screws needed
14.1
(per panel)
0
Number of fences needed
1.0
(per panel)
180
H Soldered Bracket - 2'-4 "H x TV Spacing
TRA Snow Brackets
Width of Panel (inches)
14.1
Length of Panel (feet)
3
Roof Pitch (x/12)
10
Snow Load (Lbs per ft)
180
Screw Strength (Lbs)
0
Snow Fence Strength (Lbs)
400
Number of screws needed
(per panel)
0
Number of ences needed
(per panel)
1.0
H Soldered Bracket - V -2 "H x TV Spacing