20180356 Structural ReviewPro Design
P.O. Box 699
Tracyton, Washington 98393-0699
(360) 377-1026 prodesignC seanet.com
Air management Solutions LLC April 3, 2018
5822 West Werner Road
Bremerton, WA 98312
ATTN: Bob Murphy
RE: Evaluation of replacement AC units Roof
O'Reilly Auto Parts 3742, 902 Algiers Rd, Unit 1, Yelm, WA
At your request, I have performed the evaluation the existing roof structure based on the information provided
to me. The drawing J18xxx of 2-7-18 shows the unit locations and the framing. The new unit at 610# is
replacing the existing unit (weight unknown) utilizing the existing, The roof structure consists of 44" deep wood
trusses at 48" oc. Calculations were performed on the typical roof truss and the 3 trusses carrying the unit.
The calculations found the typical roof trusses at 92% of allowable and with the units 95% of allowable. The
structural code allows the stress to be increased on existing members by up to 5% before reinforcing is
required, so the roof structure is acceptable with this change of units. Based on prior similar projects the new
units are at most 10% heavier than the existing so the original roof truss design assumed comparable weight
units.
The new unit was checked for both seismic and wind. The unit is certified to seismic levels in excess of the
site. Analysis found that wind controlled and the unit has a 1.5 FOS against overturning with respect to the
bottom of the curb, thus no tension in the fasteners. Shear was found to be 76# on each of 4 assumed
fasteners to the curb. As a #8 screw has this capacity, the fastening of the existing curb is considered
adequate.
Although only unit 2 is indicated to be replaced, this same 610 pound unit replacement applies to units 1 and 3
also. This applies until July 2019 when IBC18 replaces IBC -15. All new work of the replacement units
conforms to the 181315 with regards to the structural provisions. Please call if there are any questions or
concerns.
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John G. (Jay) Bartram S.E., P.E.