HomeMy WebLinkAbout2000-01-31 NSP Ltr to OPH Re Relocation & Structural Improvmeents PlanJanuary 31, 2000
Ms Kris Danielson
Community Development Director
City of Oak Park Heights
PO Box 2007
Oak Park Heights, MN 55082 -2007
Mr. Scott Richards
Oak Park heights city Planner
Northwest Associated consultants, Inc.
5775 Wayzata Blvd., Suite 55
Saint Louis Park, N1N 55416
Northern states Power Company
414 Nicollet Mail � RSQ 10
Minneapolis, MN 55401
Telephone (612) 330.7657
RE Kin Plant Ash
L
Stor Gara
Plans for Re locati o n o
Dear Kris and Scott;
Enclosed with this letter is a structural evaluation of the e equipment ara
garage
located at the King Plant Ash Landfill. The evaluation, performed for NSP b
. p y Barr
Engineering, assessed two concerns identified by the City: adequacies of the
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garage's structural framing and its planned foundation. NSP ro oses that the
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modifications recommended by Barr become part of part of NSP's p lans for
relocation of the garage.
Also enclosed is a plan p sheet showing the newly proposed location for the
garage. At this location, the building will be below the sight line of the surrounding
community, which should address esthetic concerns. however, the new location is
in the path of future landfill development, thus relocation or rebuilding) will be
required again In the 2004 -05 time frame, if current landfill development rates
continue.
NSP requests that the Building Permit acknowledge that the proposed
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location is temporary that the building will remain there only until future landfill
development causes re- relocation. We request to keep options open at this time as
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to where that future site might be. Factors that may be significant in assessing g
possible relocation options include NS P's s future need for landfill equipment story e
storage,
future traffic patterns in the area, what uses the closed portion of the Landfill may be
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fulfilling at that time, and whether the structure could serve some post-landfill and
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park-related uses such as a pavilion or equipment storage.
Ms Kris Danielson
Mr. seoft Richards
January 31, 2000
Page 2of2
As previously mentioned, NSP hopes to meet with city staff within the next
couple months to discuss landfill development plans and options. NSP is now
working to develop coherence to our needs, and expect to be ready to meet with the
City before the end of February. The discussion should include NSP's plans for this
summer's construction activities. An expansion will be built in an area indicated on
the attached plan sheet. construction will also include installation of security fencing
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and signage. (Fencing pending another Building Permit.)
.
1 hope this communication is sufficient to address the Garage l3uildin Permit
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issue at the February 10 Planning commission Meeting. Please contact me if there
are any questions.
Sincerely,
m
Michael R. Thames
Energy Marketing and Fuel Resources
512- 330 -7657
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January 31, 2000
Mr. Scott Thomas
BarrL neering Company
4766 West 77th Street e Minneapolis, MN 55435 -4803
Phone: 612-832-2600 Fax: 612-832-2601
Minneapolis, MN a Hibbing, MN ®Duluth, MN a Ann Arbor, Ml . Jefferson City, Mo
Northern States power Company
Ren. Square Building 7th Floor
512 Nicollet Mall
Minneapolis, MN 55401-
Dear Mr. Thomas
At your request, we have evaluated the structural framing system for the existing g pole barn on your
landfill in Oak bark Heights, Minnesota. Paul Schiller from Barr met ou at the e site on January 26,
2000 to visually review the structure and verify overall dimensions. At that ti '
time, you provided
information from your files regarding the original construction of the building, along with the
building permit and inspectors comments from the original construction. You •
u have proposed moving
the structure, and requested that Barr address the building inspectors questions .
g P q s regarding foundations
and structural framing. The following letter discusses our basic approach to the '
pp review, the
foundation design, and recommended revisions to the structure to meet UBC
code requirements for
structural load resistance. Attached are drawings of the existing building and r
g g proposed details for the
foundation and required bracing modifications.
Background
Our review was based on information on materials and member sizes athe .
g red during the site visit,
and on the sketches you provided from your files. You also rovided info '
P rmation from your files
that indicated the roof trusses were pre - engineered for vertical load resist •
once. The structure is
wooden- framed with metal roof and siding, having ominal plan dimension
g p s of 30'x48'. The eave
Mr. Scott Thomas
January 31, 2000
Page 2
height is approximately 15', with a 4:12 pitch on the roof. The roof height at the peak is about 20' .
The framing includes 5 "x6" timber posts spaced 8' on center along the 48' wails, and at 10' on center
along the 30' walls. The roof trusses are spaced 4' on center, and have knee bracing at every other
truss, in line with the posts. The walls are braced in both directions in the end bays of each wall with
2x4's. Roof purlins are 2x4's spaced at approximate) 2' on center, and wall irts are 2x4'
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at approximately 2'- on center. The roof and walls are enclosed with light -gage architectural
roofing, fastened to the purlins and girts with rubber - sealed nails.
The building is used for storage of equipment and supplies for maintenance at the landfill. The
building is unheated, and is only occupied ; briefly while maintenance is being performed at the site.
It is our understanding that utility service to the building includes only electrical supply.
Our approach to the review of the structure was to verify that the framing system could withstand
code - recommended loading conditions. we used the Uniform Building Code, 1997 edition, to
determine the loading on the structure. We analyzed the lateral load resisting system to verify that it
could withstand the design wind loading and also considered overturning of the structure and uplift
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forces on the roof. We then designed a foundation system to resist overturning and uplift forces, and
to transmit the structural loading to the foundation soils.
;ilructur
The information available on the building was limited, so several assumptions were made in order to
perform the analysis. First, the roofing and siding were not analyzed for strength, but were assumed
to be sufficient to transmit loading to the structure. It is our understanding the minor damage to the
siding or roof would not pose a threat to human life because of the infrequent use of the building.
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Second, we assumed that the knee braces were not an effective lateral -load resisting system. They
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were ignored in the analysis. Similarly, we assumed that the siding was not designed to act as a
shear panel, and we neglected the strength of the siding in the lateral resistance of the building We
assumed that the siding and roofing were sufficiently rigid to transmit the lateral loadin g to the wall
bracing. The magnitude of the lateral load is quite small, and therefore we believe that this is a valid
assumption.
We computed the total wind load based upon UBC Chapter 16, Section III. The lateral load was
assumed to be resisted solely by the wall bracing in the corner bays, and only tension braces were
Mr. Scott 'Thomas
January 31, 2000
Page 3
assumed to be effective. Based on this analysis, the existing wooden 2x4 bracing was found to be
inadequate. we then designed a steel tie -rod system to transmit the lateral wind loading to the
foundation. we designed the tie rods and connections in accordance with the AISC Allowable Stress
code and the NDS Specification for wood Construction. The system used 314" steel rod, with steel
end connections lag - bolted to the existing wooden posts. we used these same connections to attach
the posts to the foundation based on the overturning analysis results. Details of this system are
provided in the attached drawings.
We computed the uplift force on the roof trusses. Based on visual inspection, the trusses in line with
the posts appear to be attached securely to the posts., but the intermediate trusses do not appear to
have a positive connection to the walls.. On the drawings we have included a recommendation for
attaching the intermediate trusses to the walls, we then checked the roof purlins for load capacity
based on comments from the building inspector that these members were overloaded. we used 1000
psi as the basic allowable flexural stress (F of the purlins, assuming that the wood was spruce-pin-
fir construction grade. we then applied modification factors for flat use, load duration, and repetitive
members. we found that when these modification factors were applied, the computed snow load
stress in the purlins did not exceed the allowable stress.
The foundation system was designed to resist overturning of the structure, with a minimum safety
factor of 1.5 (per UBC requirements). The n1inimurn depth of the footing according to Minnesota
Rules is 3'-6". Based on our discussions, we considered using individual round piers as footings, and
assumed that the subgrade would be compacted Class V aggregate, extending to below the footing
depth. Based on this system, the bearing capacity of the subgrade is expected to exceed 2,040 psf.
The controlling load case for the footing design was uplift due to wind loading, particularly for the
corner footings where the tie rods are attached. The required footing size was 24" diameter,
extending to a depth of 4'-6". we included reinforcing in the footing to resist shrinkage or
temperature cracking of the concrete. Details of the footing and material specifications are shown on
the drawings. Based on your description that the site will be prepared by compacting the Class V
aggregate in lifts, it is our opinion that moderate settlement of the footings is not expected, and
would likely not result in damage to the structure, therefore we did not perform a settlement analysis.
Mr. Scott 'Thomas
January 31, 2400
Page 4
Site Location
We did not have access to a site map, and therefore we were unable to show the lan view location p o at�on of
the structure on the site. We did discuss the location with you durin our site visit. It is ou
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understanding that you will obtain a site ' map and sketch the ro osed location for the building
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inspector. A hand sketch was provided for the original building rmit, and should be adequate g p for
the current evaluation.
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It is our opinion that the existing structure requires modifications to the lateral bracing system, g y m, and
should have the intermediate trusses positively attached to the walls in order to meet code
requirements. We have included details for a footing system previously described. We have
prepared drawings that can be used for construction of the footings and bracing/connections.
If you have any questions or comments regarding this letter, please contact us at the number listed
s ed
below.
Sincerely,
Paul Schiller, P.E.
Civil Engineer
(612)832 -2668
attachments