×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Sydney Hail Storm - Steel Framed Factory Collapse

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.






RE: Sydney Hail Storm - Steel Framed Factory Collapse

It looks like a flat roof- they don't get hail much and rarely of that scale.

http://www.eng-tips.com/threadminder.cfm?pid=1529
Use translation assistance for Engineers forum

Note the rules include No Student posting

RE: Sydney Hail Storm - Steel Framed Factory Collapse

All look like "pre-engineered metal buildings" (PEMB's).....those structures are severely "optimized" (structurally) and were likely not designed for such accumulations. They typically have a 1:12 or 2:12 slope, so they are relatively flat and the localized deflection of the panels and purlins exacerbates the issue.

RE: Sydney Hail Storm - Steel Framed Factory Collapse

Agree with above two posts. Totally understandable.

Mike McCann, PE, SE (WA)


RE: Sydney Hail Storm - Steel Framed Factory Collapse

Sometimes they go to 1/2" per foot as well.

Check out Eng-Tips Forum's Policies here:
FAQ731-376: Eng-Tips.com Forum Policies

RE: Sydney Hail Storm - Steel Framed Factory Collapse

Those roofs are relatively flat, with steel roofing. Only pitched enough for water to run off, not hail. We do get big hailstorms in many areas of Australia, and they invariably lead to failures, but not usually of this magnitude. The most common type failure is filling of box gutters, then when melting starts, water runs back into the building.

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

(OP)
Must have been a huge dump of hail in a very short time. I made the mistake of thinking rain runoff would be the same as ice.

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

Yes, I think it should be a load case. There have been a lot of buildings damaged by hailstorms. Hail usually occurs with rain, and when the ice blocks internal drains and box gutters, the water as well as the ice has nowhere to go.

RE: Sydney Hail Storm - Steel Framed Factory Collapse

That's why most roofs here have a minimum live load of 20 psf - construction related. Snow still controls though overall. It would well cover the hail load.

Mike McCann, PE, SE (WA)


RE: Sydney Hail Storm - Steel Framed Factory Collapse

(OP)
I would have thought this would just cause the gutter system to fail and thus relieve the accumulation.

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

I don't really have a formed opinion as to the magnitude of loading which should be codified.

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

hokie66 - I think your point about drainage is very applicable. I had a large snowstorm occur in San Antonio, TX back in the 1980's with quite a few roof collapses - most occuring due to either poor construction or clogged roof drains and the resulting ponding (melting happened almost within 24 hours of the storm).

Ice and snow can clog drains quickly - especially ice/hail I would bet.

Check out Eng-Tips Forum's Policies here:
FAQ731-376: Eng-Tips.com Forum Policies

RE: Sydney Hail Storm - Steel Framed Factory Collapse

Quote (hokie66)

I doubt those buildings are PEMB as you think of them, because we don't have much of that in Australia.

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.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close