Sydney Hail Storm - Steel Framed Factory Collapse
Sydney Hail Storm - Steel Framed Factory Collapse
(OP)
Sydney, Australia copped it pretty bad this week in terms of storms and flooding.
This afternoon was particularly bad with large amounts of hail. Several steel framed buildings collapsed due to accumulation of hail on the roof.
My question is how did the hail accumulate? Surely the pitch of the roof would prevent this? Pictures below.




This afternoon was particularly bad with large amounts of hail. Several steel framed buildings collapsed due to accumulation of hail on the roof.
My question is how did the hail accumulate? Surely the pitch of the roof would prevent this? Pictures below.









RE: Sydney Hail Storm - Steel Framed Factory Collapse
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RE: Sydney Hail Storm - Steel Framed Factory Collapse
RE: Sydney Hail Storm - Steel Framed Factory Collapse
Mike McCann, PE, SE (WA)
RE: Sydney Hail Storm - Steel Framed Factory Collapse
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RE: Sydney Hail Storm - Steel Framed Factory Collapse
Ron, I doubt those buildings are PEMB as you think of them, because we don't have much of that in Australia. But we do have all too many substandard old warehouse and factory structures which are even worse than your PEMB structures. As snow load is not an issue in most of Australia, hail is often forgotten as well. And many buildings are "designed" for only .25 kPa live load (about 5 psf).
Hopefully, we can get some more information about how those buildings were structured.
RE: Sydney Hail Storm - Steel Framed Factory Collapse
I've honestly never considered hail accumulation. Increase the minimum live load? Have a minimum pitch for roofs?
RE: Sydney Hail Storm - Steel Framed Factory Collapse
RE: Sydney Hail Storm - Steel Framed Factory Collapse
Mike McCann, PE, SE (WA)
RE: Sydney Hail Storm - Steel Framed Factory Collapse
What do you think a ballpark figure for hail loads should be? Reoccurrence period? Load combo = 1.2G + 1.2SDL + 1.5Hail? Have you ever actually designed for this? Did it kill your frame?
Interested to hear your opinion/experience.
RE: Sydney Hail Storm - Steel Framed Factory Collapse
Most of my experience in Australia has been in high wind areas, so the wind loading generally controls.
The somewhat separate issue of roof drainage, especially involving any kind of internal drains, also needs a fresh look. This is sometimes left to architects, but in recent times hydraulic consultants are frequently involved. The roofs which collapsed in Sydney had internal gutters.
RE: Sydney Hail Storm - Steel Framed Factory Collapse
Ice and snow can clog drains quickly - especially ice/hail I would bet.
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RE: Sydney Hail Storm - Steel Framed Factory Collapse
I agree. It is interesting that Butler Manufacturing™ - one of largest PEMB in the US - are owned (and have been for more than a decade) by BlusScope in Australia, but the concept of PEMB never took off in Australia, except for possibly rural/ag/farm buildings/sheds.