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325 West 13T"Avenue
g EIIJOHNSON
BRODERICK Eugene,Oregon,97401
541-338-9488(office)
ENGINEERING 541-338-9483(fax)
wwwiohnsonBroderickEngineering.com
Paul Tibbot
FDH Velocitel
4004 SW Kruse Way Place, Suite 220
Lake Oswego, OR 97035
Re: Upgrade to Roof Framing at Supports for Proposed Panel Antennas
6975 Southwest Sandberg Road,Tigard, Oregon, 97223—AT&T Site PR35
Paul,
Per your request,Johnson Broderick Engineering has reviewed the failing structural analysis we
submitted to you regarding the addition of larger panel antennas and associated equipment to
existing non-penetrating rooftop skids, located atop an existing commercial building at 6975
Southwest Sandberg Road in Tigard, Oregon.
Our previous analysis showed that the skids required at least 37 8 inch CMU blocks at each
ballast tray to prevent the skid from overturning, and that the existing roof framing did not
have adequate capacity to support this additional load. Therefore,we calculated what would
be required at the roof framing to support this load. The existing framing consists of 2 x 12
joists spaced at 24 inches on center,which bear on steel beams. The results of a previous
structural analysis that we were provided with demonstrate that the steel beams are adequate,
therefore it is our assumption that our scope of work is limited to upgrading the existing roof
joists only. Additionally,we understand that due to space limitations, you will be upgrading the
skids to new Valmont RTP12 non-penetrating roof skids. We have taken the weight of this new
skid into account in our analysis. Our findings are as follows.
Existing 2 x 12 wood joists that support any of the non-penetrating roof skids are to have an
new 1-3/4"x 11-7/8" 1.9 MicroLam LVL joist sistered to the existing joist and fastened per the
attached detail. Contractor is to forward information regarding the attachment of the existing
joists to the steel beam for engineer's review so that a proper connection can be specified. This
is a deferred submittal based on the contractor forwarding this information.
We appreciate the opportunity to be of service. Please call if you have any comments or
ques '
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Revision 0 June 22,2016
JBE project No. 15024.15
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325 West 13th Avenue
B JOHNSON Eugene,Oregon 97401
- jB R O D E R I C K 541-338-9488(office)
ENGINEERING 541-338-9483(fax)
www.JohnsonBroderickEngineering.com
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Location:Worst-case upgraded roof beam-ballast load at both ends,load d a,iiJC . Johnson Broderick Engieering,LLC Z
Multi-Loaded Multi-Span Beam 325 West 13th Avenue
[2012 International Building Code(2012 NDS))
Eugene,Oregon,97401
(2)1.5 IN x 11.25 IN x 18.0 FT
#i &Btr-Douglas-Fir-Larch-Dry Use StruCalc Version 9.0.2.5 6/22/2016 5:57:50 PM
Section Adequate By:29.3%
Controlling Factor:Moment
CAUTIONS
'Laminations are to be fully connected to provide uniform transfer of loads to all members
DEFLECTIONS Center LOADING DIAGRAM
Live Load 0.18 IN U1172
Dead Load 0.33 in
Total Load 0.51 IN L/422
Live Load Deflection Criteria:U360 Total Load Deflection Criteria:U240
REACTIONS B g
Live Load 450 lb 450 lb
Dead Load 539 lb 1593 lb
Total Load 989 lb 2043 lb
Bearing Length 0.53 in 1.09 in R -_1" „h
BEAM DATA Center W
Span Length 18 ft
Unbraced Length-Top 2 ft 18 n
AL
Unbraced Length-Bottom 18 ft
Live Load Duration Factor 1.15
Notch Depth 0.00
MATERIAL PROPERTIES UNIFORM LOADS Center
#1 &Btr-Douglas-Fir-Larch Uniform Live Load 50 plf
Base Values Adjusted Uniform Dead Load 30 plf
Bending Stress: Fb= 1200 psi Fb'= 1372 psi
BeamSelf Weight 7 plf
Cd=1.15 C1=0.99 CF=1.00 TotaallUniform Load 87 plf
Shear Stress: Fv= 180 psi Fv'= 207 psi TRAPEZOIDAL LOADS-CENTER SPAN
Cd=1.15 Load Number One
Modulus of Elasticity: E= 1800 ksi E'= 1800 ksi Left Live Load 0 plf
Comp.1-to Grain: Fc--I-= 625 psi Fc-1'= 625 psi Left Dead Load 292 plf
Right Live Load 0 plf
Controlling Moment: 5597 ft-lb Right Dead Load 292 plf
11.34 Ft from left support of span 2(Center Span) Load Start 13 ft
Created by combining all dead loads and live loads on span(s)2 Load End 18 ft
Controlling Shear: -2043 lb Load Length 5 ft
At right support of span 2(Center Span)
Created by combining all dead loads and live loads on span(s)2
Comparisons with required sections: Reo'd Provided
Section Modulus: 48.96 in3 63.28 in3
Area(Shear): 14.8 in2 33.75 in2
Moment of Inertia(deflection): 202.58 in4 355.96 in4
Moment: 5597 ft-lb 7234 ft-lb
Shear: -2043 lb 4658 lb
NOTES