×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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!
  • Students Click Here

*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

Jobs

Snow Drift

Snow Drift

Snow Drift

(OP)
I'm designing a beam that is carrying both a high roof as well as a low roof and was wondering if the snow load on the high roof would be reduced and by how much due to the snow from the high roof blowing off and drifting on the low roof?

RE: Snow Drift

Seems like a moot point if the beam is carrying both anyway.

Mike McCann
MMC Engineering

RE: Snow Drift

(OP)
I'm saying is it loaded with the snow load from upper roof, snow load from lower roof, and the drift loading; or is it a reduced load from upper roof, snow load from lower roof, and the drift loading. I'm asking because the drifting snow would come from the upper roof leaving less than full snow on the upper roof, instead of basically doubling the snow load. Sorry for the confusion.

RE: Snow Drift

I would not reduce snow on the high roof if drifting snow is the only factor, i.e. if the high roof is flat. In Canada, if the high roof is sloping and the low roof is designed for drifting plus sliding snow, the high roof snow load may be reduced in accordance with Commentary G, Article 41 of User's Guide NBC 2005 - Structural Commentaries. This may not be true of other codes.

BA

RE: Snow Drift

BA time to update your reference... NBC 2010 and the new commentaries. but the article reference is still the same

RE: Snow Drift

Sorry about that, jayrod. I have been retired for six years so I am a little out of date.

BA

RE: Snow Drift

No apologies necessary. Just keeping you up to date (It's tough to stay up to date when you aren't working as close to the action anymore). Hope you are enjoying your retirement. I look forward to mine in about 25 years or so.

RE: Snow Drift

ASCE7-02 to -10 do not allow reductions for higher roofs when evaluating drift loads that I'm aware of except in the event that you can justify using different exposure categories for the two roofs. Also, remember to check your windward and leeward drifts separately.

I think the only exception to this is for sliding slow loads which are assumed to be caused by balanced snow load sliding from one roof to another and thus would not need to be considered at the same time but you will want to check this with ASCE to be sure.

Lastly, remember that code level snow loads are often due to multiple slow events. Thus, it's not inconceivable that one snow storm could occur during a high wind event and deposit drift loads and then the other could occur with limited wind and add a balanced load on top of everything.

Maine EIT, Civil/Structural.

RE: Snow Drift

That should say "multiple SNOW events" in the final paragraph.

Maine EIT, Civil/Structural.

RE: Snow Drift

Oh man, I'm out of it, I made the same typo in the 2nd paragraph... I need more coffee.

Maine EIT, Civil/Structural.

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!


Resources