HomeMy WebLinkAbout411 S BRYAN AVE - SPECIAL INSPECTIONS - 3/25/1986Douglas Rutledge & Company
Structural Engineering • Steel Detailing
200 E. Seventh Street, Suite 416
Loveland, CO 80537
3031669-1748
March 25, 1986
Mr. Carl Glaser
Glaser and Associates
215 Jefferson Street
Fort Collins. CO 80524
Re: Structural Investigation
Club House Project
Project 11002
Dear Carl:
This letter will serve to confirm our recent telephone
conversation concerning the roof truss analysis on the
referenced building. We have looked at the assumption of
using the intermediate roof purlins to support the 2' x 6'
ridge beam. In order to describe this approach, please
refer to the sketch made by Bonnie Oliver. First of all, we
looked at the top chord member spanning from joint 1 through
4. The stresses were checked and the 2" x 6" member can not
span between joint 1 to joint 4. Thus the intermediate beam
(b) is required. This beam will be overloaded as shown in
the calculations and will need to be replaced or built up.
Next we looked at the possibility of taking the tributary
roof load transmitted into the ridge beam (a) and
distributing this load into the intermediate roof purlins
acting as compression members. The stress levels were found
to be within the allowable limits with this approach, thus
indicating the beam would not need to be replaced.
Also, we analyzed the main roof truss with this new scheme
and found that roof member 1-2 was over stressed with the
full design snow load of 22 P.S.F.. In order to keep the
stress levels within the allowable limits the snow load
would have to be reduced to 15 P.S.F.. In order to put this
into perspective, the 15 P.S.F. would equate to
approximately 18 inches of wet snow. This is a sizable
storm but would not meet the design snow load requirement
used in common practice in the Fort Collins area.
The bolted connections are still over stressed and will need
to be modified. The solutions to remedy this would be to
add bolts or increase the diameter of the existing bolts.
As we mentioned in our previous letter, some cracking of the
wood members has occurred around the bolts. The extent of
the cracking is not known. However due to the high stress
levels, we recommend that each joint be inspected to
determine the extent of this cracking and thus establishing
a basis for repair.
Again we appreciate working with you on this project and if
we can help you further please let us know.
Sincerely Yours,
DOUGLAS RUTLEDGE & COMPANY
Wi 'ston E. Knechtel
Chief Structural Engineer
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G I_ A S
March 28, 1986
P A
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Ms. Leslie Beckmann.
Department of Parks & Recreation
City of Fort Collins
413 South Bryan
Fort Collins, Colorado 80521
RE: City Park Nine Clubhouse,
Roof Structure
Dear Leslie:
C A
I have attached a copy of Win Knechtel's letter revising his findings on
the roof structure plus a print of his marked up drawings for your
review. I would like to clarify the issues and posible solutions with
this letter.
After receiving Win's March 10, 1986 recommendations, I reinspected the
roof structure. I examined four trusses at the east end of the building
looking primarily at joints 3 and 5 (see Win's sketch) in the bottom
chord, i.e. I inspected eight joints. The bottom chords are double 2 x
6's with two rows of two bolts in each joint. I found four joints with
cracks across the upper row of bolts on one side and one joint with
cracking across the upper row of bolts on two sides. None of the
inspected joints had cracking across the bottom row of bolts and,of the
four joints with cracking on one side, the companion 2 x 6 chord showed
no signs of cracking.
My observation was that the trusses had not shown the results of severe
stress although the" ceiling has been heavily insulated and Fort Collins
experienced a record snowfall this past winter. I did not observe any
cracking in the ridge beam (joint 4) or any significant cracking in the
various web members (joint 2 to joint 3 and joint 5 to joint 6). My
observations did generate concern about the intermediate supports (at
joints 2 and 6); the cross beams appeared light and were not tied into
the structure in an acceptable manner. The above were only field observa-
tions and in no way may be regarded as conclusive, however the observa-
tions have merit from the standpoint that it is a means of evaluating the
long-term performance of an unconventional framing system. These observa-
tions do not warrant what shall occur in the future.
As a result of my observations, Win's current findings takes the past
performance of the members into account. Consequently our recommendation
is to maintain the existing roof structure with the following provisions.
Ms. Leslie Beckmann
March 28, 1986
Page 2
1. Intermediate beams "b" at ,joints 2 and 6 must be replaced with larger
members and improved connections.
2. Where the interior design allows, we shall provide intermediate
bearing for the trusses. However, in areas where intermediate bearing
is not feasible, the existing connections will require improvement.
3. Install a standing seam metal roof to encourage snow to slide off.
4. City accepts 15 p.s.f. snow loading where intermediate bearing is not
practical. (Note: City of Fort Collins typically requires a 30 p.s.f.
snow load which can be reduced to 27.5 p.s.f. due to the roof slope.)
As part of the construction, I recommend the entire existing ceiling be
removed to facilitate inspection and repair of the joints and replacement
of the intermediate beams "b". It is not practical to accomplish these
tasks working around the existing insulation and ceiling plane. It is
imperative that we have an opportunity to fully inspect the structure
during construction.
In conclusion: I feel it is cost effective to work with the existing
structure rather than replace it with a totally new structure. There are
risks involved with the existing structure that would ultimately have to
be accepted by the City, however these risks are identifiable and can be
reduced through the .new design. We propose to work with the building
department to arrive at the most practical solution.
We are proceeding with the preliminary design based on the above recom-
mendations. I request written confirmation on the City's position.
Very truly yours,
GLASER ASSOCIATES ARCHITECTS
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Carl J. Glaser, AIA
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Enclosures
cc Jared Interholzinger
Felix Lee
Win_Knechtel