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  • Sample report of a structural investigation - Roof panel damage


    BUILDING INVESTIGATION

    Project Name: Pre-engineered metal building - roof panel damage investigation.

    Project Location:

    Submitted to (Attorneys At Law)

    Submitted by Thomas R. Price P.E., of Structural Solutions LLC, a licensed professional engineer


    I. Purpose of Investigation:

    At the request of the owners' Legal advisors, Thomas R. Price P.E., of
    Structural Solutions LLC inspected the Facility in the attempt to determine the cause of apparent damage to the metal standing seam roof panels. In addition, inspection of a base girt anchorage was requested and carried out.

    II. Description of Building:

    The building in question is a metal building manufactured by an AISC MB certified producer, designed to Metal Building Manufacturers Association specification.

    The building is comprised of a 120’ wide by 75’ long gable roof building connected to
    an 80’ wide by 156’ long single slope roof building. Roof slopes are 1:12. (ref. Fig. A)

    The roof is a 24” wide 24 ga. galvalume standing seam system. Roof panel splices exist on 80’ roof areas, with panels approximately 40’ long being utilized. Frame spacings are 25’. Purlins are cold-formed zees with 5’-6” spacings typical.


    III. History:

    Building manufacturer drawing dates indicate that the building is less than two years old. Some time after the roof was installed, damage to roof panels was discovered. This damage exists in two distinct areas of the roof. (ref. Fig. A - areas “A” & “B”). A search for the cause of this damage ensued, including this office being brought in
    to investigate.


    IV. Referenced Documents:

    Metal building system manufacturer drawings.
    Project drawings, by Project Architect.


    V. Field Observations and Notes:

    The inspection took place between 1:00 pm and 3:30 pm. Weather was clear, with a temperature of approximately 60 F. Present on the site was representatives of the contractor, the owner, and Mr. Price. Our comments relative to the inspection of the main building are listed below.

    It must be noted that all details and materials of construction are not readily visible and verifiable without some disassembly of the building system. No disassembly was done during the inspection.

    Area A:

    1) Across approximately 25 roof panels, a line of damage exists consisting of panel
    distortion and localized buckling of the panel material. The damage is within a few
    inches of each panels’ midpoint (20’ from end of 40’ panels). The damage location
    shifts up and down slope +/- 4”: From the north, the damage location is consistent
    across about 8 panels, then shifts downslope 4” across 9 panels, then shifts 4” down-
    slope across 1 panel, then upslope 4” across 3 panels, then downslope 4” across
    4 panels. Some panels display more damage than others, but there is a distinct
    start and end of the line of damage.

    2) The roof panel deformations are consistent with that caused by excessive bending at
    the damaged location. Specifically, negative bending (ribs in tension, flat region in
    compression), was the cause of the damage. The ribs are bowing upwaDr, as
    installed, indicating elongation and therefore tension in the ribs. The bottom, flat
    region of the panels are buckled, indicating compression in the flat region.

    3) Damage to some of the ribs is such that the weather tight seal between adjacent
    panels is questionable. Hammer marks on some of the ribs indicate an attempt
    to straighten the rib region, probably to get the ribs to engage and seal. There is
    evidence of water collecting in the depressions at damage locations.

    4) The location of the damage relative to the panel support points (i.e. the 66” spaced
    purlins) is variable, due to the shifting of the damage location from panel to panel.
    (See Figure B). The damage falls as close as 2” from midspan, and as far as 9”
    from midspan. If the damage occurred after the panels were installed, only an upwaDr
    force on the panels can cause the type of damage present. Wind uplift is the only
    environmental load that could cause this damage.

    If a uniform uplift load is applied to the panels, the resulting bending force
    at the supports (negative bending) is approximately 3 times the bending force at
    midspan (positive bending). Th building manufacturer's published panel section properties indicate that their
    24 ga. standing seam roof panel has nearly equal allowable moments for positive and negative
    bending. This would indicate that excessive wind uplift will damage the panels
    at the supports first, however, no damage was apparent at the supports.

    If wind uplift were the cause of damage, the damage locations would not be
    suddenly moving up and down slope in stairstep fashion, as observed.

    The amount of buckling that exists would require large midspan deflections
    inconsistent with complete lack of damage at the supports.

    5) The possibility of damage to the panels occuring prior to installation must be
    reviewed. The damage locations are nearly centered on the 40’ panels.
    The metal building manufacturer's drawings indicate that a spreader beam be utilized in picking
    up bundles of panels which exceed 25’ in length. If the panels were picked
    up by a hoist attached just at the center of the bundle (no spreader beam),
    the resulting damage would be quite consistent with the damage observed:
    Ribs go into tension, flat region into compression, and large deformations
    occur. The stairstepping of the damage location is possibly due to the panels
    sliding during the pick, or being stacked in a manner where the panel ends are
    not all lining up in the bundle.

    If a bundle of panels were to fail in this scenario, it is likely that the panels towaDr
    the bottom of the bundle would suffer more damage than those towaDr the top of the
    bundle. This would explain the variability of the extent of damage from panel to
    panel.

    The metal building manufacturer has indicated that a maximum of 30 panels are packed in each bundle.
    The observed damage was to 25 consecutive panels.


    Area B:

    1) Damage in this area affected 4 panels. The deformations are similar to area A
    However, there are three locations along the panels exhibitng damage. These
    locations, like area A, do not coincide with the locations of maximum bending,
    where damage would occur first under wind uplift.

    2) There is caulk on the side of the panel rib at two or more damage locations.
    It appears to be covering holes in the panels, though it was not removed to
    confirm this.

    Base Girt:

    1) An inspection of one segment of the exterior building wall was unable to find any anchorage of the base girt to the foundation.

    2) Building manufacturer drawings indicate 2 -3/8”dia. expansion bolts at 4’-0” spacing is required for base girt anchorage.


    VI. Conclusions:

    The most likely cause of the roof panel damage was some sort of mishandling of the panels prior to installation.

    Damage in area A is consistent with what can be expected when a bundle of panels is hoisted by picking them up with a single pick point at mid length of the panels. It is not consistent with damage that would occur due to wind or gravity loads.

    Damage in area B is not consistent with what would be expected from wind or gravity loads. Some sort of mishandling prior to installation is more likely.


    VII. Recommendations:

    It is recommended that the most likely cause of panel damage be investigated
    further; the handling of the panels prior to installation. This would include
    the manufacturer's handling of the panels in their shop, handling of the panels during loading onto
    truck, shipping, handling of the panels during unloading at site, and handling of
    panels as they were hoisted onto the roof and installed.

    The erector should be consulted as to when damage was first noticed, when was
    caulk applied to ribs and why, whether an attempt was made to beat the panels
    back into shape with a hammer or similar instrument, whether the panels were
    lifted accoDring to manufacturer guidelines, and whether any incidents occurred during lifting
    operations where the panels underwent large deformations, slid, tilted, bent, sagged
    excessively or were subjected to any other unusual conditions.

    The building manufacturer should be consulted to determine the warrantability of their
    product, given its current condition. Also, they should be able to pass some opinion on
    the weather-tightness of their panels, given their current condition.



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1200 Troon Ct. SE
Grand Rapids, MI 49546
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