HomeMy WebLinkAboutTruss Analysis Engineer Report 06.21.17SSGM
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RE:
June 2t,2Ot7
Mr. Rich Musgrave
227 Rio Bravo
Silt, Colorado 81652
Truss Analysis
Shop Trusses
Dear Rich,
At your request, SGM has completed an evaluation of the trusses that have been placed on your
proposed shop locatedat22T Rio Bravo, Silt, Colorado. The truss construction is generally described as
follows in Figure 1 (from your original building permit application):
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Figure 1- General Truss Configuration
The truss spacing is observed to be at 48" o.c. and is proposed to be fastened to the supporting walls
using 2 Hurricane clips per connection (ie., 4 per truss). From the sketch, the top chords for the trusses
are 2x6 and the remaining members are 2x4 members. Given the fact that the trusses were
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{,;!.it'J!VCi-}t} :pRlNG:i ll8 West Sixth St, Suite 200 | Glenwood Springs, CO 8ló01 | 970.945.1004
SSGM
premanufactured trusses, the wood species for the trusses is likely Douglas
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Fir MSR lumber.
Unfortunately, no markings indicating the strength of the lumber was observed, thus our evaluatíon
considered allowable stress comparisons for Douglas Fir Larch Select Structural categories. The joints
are connected using both plywood and metal gussets.
From ourdiscussion, these trusses were removed from the upper Roaring Fork'Valley on a previously'
constructed barn for 75 psf snow load conditions when spaced al 24" o.c. For the current location,
south of Silt, in Garfield County, the new conditions are to resist a 40 psf snow load in accordance to the
County's adoption of the 2015 lBC. The trusses located at each end of the proposed shop were
evaluated to have adequate strength for the new loading conditions. For the interior trusses, the 2x6
top chords, given the doubled tributary span for snow load conditions, failed in bending. The remaining
2x4 members all had adequate strength to support the new load conditions. Thus, we are
recommending that you provide a "sistered" 2x6 to the top chords of the trusses that are subjected to
the 48" tributary loading (ie., interior trusses). The 2x6 sister members can be Douglas Fir Larch #2 or
better lumber, free of nots and defects. We would recommend glue and nailing to the existing member
using P1400 or equal glue and 16d nails staggered and spaced at L2" o.c. Likewise, we would
recommend nailing the 2x4 roofing support nailers to both the existing top chord and the sistered
member to assure lateral support exists in the compression (top) edge of the member.
ln lieu of a "sistered" 2x6, you may also opt to use twoTo" x5 tf2" plywood members, one on each side
of the top chord of the truss, also glue and nailing to the top chord (only using 8d nails, staggered at L2"
o.c.).
ln summary, excepting the top chord of the interior truss members which have suggested modifications
above, the trusses installed for you shop will have adequate strength to meet the loading requirements
for the Garfield County Building Code.
Upon your receipt and , if you have any questions, please don't hesitate to contact me
ly,
s.
ä81 52
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GLtl.J!'Vff*D !lRiNGS I l8 Wesl Sixth St, Suite 200 | Glenwood Springs, CO 8ló01 | 97A.945.1004