Metal Ceiling - partial collapse

[PSUengineer1]

Thank you for reading. I have an R-panel metal ceiling (3-foot wide sheets). The ceiling attaches to 2x4 wood nailers (laid flat). Nailers spaced every 30 inches and nailed to truss bottom chords with 2 to 3 10d nails. Trusses are at 6-foot centers. This is in a large storage faciltiy. No collateral evidence of wind damage to building (no metal roof panels displaced, etc.). No water damage. No wood rot. No heavily rusted nails. About 6.5 inches of batt insulation is on top of the metal ceiling. I would think the 24 Gage metal ceiling can hold the weight of insulation. Wondering if nails just backed out because they were nailed in direct withdrawl (not toenailed) and expansition and contraction of wood (hygrometric environmental changes). I don't think wind could cause such a failure. looking for input on attached photos. Thank you in advance!

 

[ANE91]

Just run the numbers on smooth-shanked nail withdrawal to see what’s plausible. It doesn’t matter whether the ceiling itself can bear the insulation if the connections themselves are inadequate. You don’t mention a truss spacing, but if it is truly the case that only 3 nails affix the furring at each truss in sustained tension, then this failure is unsurprising. Insulation doesn’t look blown about, so there must be something else that’s making you think about wind. Are the downspouts ripped off? Is the roof covering removed at the corners, etc? Are there any large windward openings that make you think the building was inflated?

 

[PSUengineer1]

Just run the numbers on smooth-shanked nail withdrawal to see what’s plausible. It doesn’t matter whether the ceiling itself can bear the insulation if the connections themselves are inadequate. You don’t mention a truss spacing, but if it is truly the case that only 3 nails affix the furring at each truss in sustained tension, then this failure is unsurprising. Insulation doesn’t look blown about, so there must be something else that’s making you think about wind. Are the downspouts ripped off? Is the roof covering removed at the corners, etc? Are there any large windward openings that make you think the building was inflated?

Thank you, ANE91. I have no reason to believe it is wind. Good observation on your point that the insulation is not disheveled. I definitely saw no signs of wind on outside of building. Trusses are 6 feet apart so I highly anticipate failure in nail withdrawal once I run the numbers. Thanks again!

 

[LittleInch]

Well if I'm looking at this correctly, some of your bits of 2 x 4 battens were jointed at a truss by your three nails both into the same truss butting up to each other.

The whole installation looks very poor and how anyone expected that to last is just asking for it. You've actually got a decent dead load so add on any wind load this will be your weak point. Lose one connections and the rest will fail rapidly.

 

[Rabbit12]

Use screws.

 

[mfgenggear]

While is not my specialty.
#1) what is the main cause of failure.
List of possibilities.
I not a fan of nails worked on projects bearing load would be lag screws.
Or bolted joints . I talking out my rear end but
Lost pre load added to loss of friction and appling loads to the nails shear and tension.
Is there possibility of wind causing vibration and moments on the joints?