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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 kn G I_ A S March 28, 1986 P A J J 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 copv Carl J. Glaser, AIA CJG:tjgk Enclosures cc Jared Interholzinger Felix Lee Win_Knechtel