HomeMy WebLinkAboutCOR-1997-Rockery - WILSON &ASSOCIATES, CONSULTING ENGINEERS
26621 SE 172ND ST.
ISSAQUAH. WASHINGTON 98027-8297
FAX(425) 313-0380
(425) 392-8996 OR 392-8947.
July 8, 1997.
Don Measamer
Building Inspector.
City of Anacortes.
P. O. Box 547.
Anacortes, Washington 98221.
Subject: Anaeortes Senior Housing.
Dear Mr. Measamer:
The Contractor informed me that a rockery adjacent to the alley was in question.
Specifically, the question was whether the rockery was able to support the weight of a City
owned garbage truck weighing some 30,000 Lbs.
The truck has AASHTO HI5-44 loading, which means the front axle has an applied
!oadinq of 6,000 Lbs., and the rear axle has an applied loading of 24,000 Lbs. Therefore
maximum wheel !oading is 12,000 Lbs.A somewhat modified application of Boussineso
allows the use of a trapezoidal loading near the bottom .8 Ft. of the retained earth. Since the
rockery is set into the grade by about 1 Ft. a total load is based upon 1.8 Ft. at the bottom of
the rockery. A set of calculations is included herein for your review. The area of the tire tread
applying the load to the pavement is based upon a rectangular foot print of 8"X 10-for both
tires. It is somewhat more conservative to assume the overlap of pressure as being additive.
Therefore, I have used a factor of 2 for the applied pressure.
A detail of the rockery was furnished the Contractor. The rockery has a safety factor
against overturning of slightly over 1.5 and 1.5 for sliding. The rockery appears to be
adequate for the back fill and applied H15-44 loading.
Should you have any question or comments regarding this analysis or letter. please call
me immediately.
Sincerely
AS W
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