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• Sample of building investigation

  
  
  
  BUILDING INVESTIGATION
  
  I. Purpose of Investigation:
  
  Preliminary analysis of roof purlins and main frames to determine nature and extent
  of reinforcement necessary to accommodate building modifications. Installing additional
  roof top mechanical units and new roofing are the modifications being examined in this report.
  
  II. Description of Building:
  
  The building in question is a metal building manufactured by MBMA manufacturer. Dimensions
  are 100'-0" x 200'-0" x 20'-0" eave, symmetric gable 1/2: 12 roof.
  
  III. History:
  
  NBS documents indicate original construction occurred in 1995.
  
  IV. Referenced Documents:
  
  Architect drawings S21, S22, S23, S24, S25.
  
  Mfg. construction drawings.
  
  V. Field Observations and Notes:
  
  Field inspection took place Tuesday, for the purpose of reviewing the intended
  building modifications.
  
  VI. Investigation Results:
  
  Roof purlins:
  
  The existing purlins are 5 span continuous (lapped), 10" light gauge steel zee shapes.
  Spans are 27'-0", 3 @ 28'-4", 27'-0". They are 5'-0" o.c.
  
  Mfg. drawings indicate purlin material thicknesses of .105", .086", .076", .086", .105"
  for the 5 spans.
  
  Under original loadings plus 2 psf for additional roofing, the existing purlins are at
  105%, 80%, 85%, 80%, 105% of their capacities for the 5 spans. The 5%
  apparent overstress can be justified by considering it to use up 2 psf of the original
  10 psf collateral dead load, leaving 8 psf remaining for mechanical and ceiling weight.
  
  3 of 5
  Additional justification lies in the Code provision K602.1, which allows for structural
  modifications that increase stresses less than 5%. Of original 48 psf total gravity roof
  load, 2 psf represents 4.2%.
  
  If the roof is to also meet a 42.4 psf roof snow load, (7.4 psf more than original 35 psf),
  the typical purlin will be in the range of 5 to 20% overstressed. This would necessitate
  reinforcing all purlins along their full length, or adding additional purlins throughout
  roof, to cut the spacing from 5'-0" to 2'-6" ("doubling").
  
  The regions at and near roof units will require purlin doubling, and special bracing:
  
  Main Frames:
  
  The existing frames are 6 span rigid frames with column to rafter fixity at all columns.
  
  Under original loadings plus 2 psf, the existing frame members show overstress (5%) at
  only 2 locations. A few web shear stiffeners can take care of this. Note:
  Frame connections have not been reviewed at the time of this report.
  
  Various frame reinforcing will be required in the regions at and near the roof units:
  
  
  
  Foundations:
  
  Foundation investigation not in current scope of work.
  
  VII. Additional Comments:
  
  AHU-2 is located at the building ridge, which can create problems with roof panel
  thermal expansion stresses. Using short steel posts bearing upon WF beams may
  be a better approach. The only penetrations through the roof are the posts, and the
  ducts.
  
  This approach may be worth considering for the other units, especially the heavier ones.

  
  
  

Contact Information

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(517) 467-6145 

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Structural Solutions LLC

8466 Slee Rd.

Onsted, MI 49265

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General Information:     Thomas R. Price, P.E.

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