×
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 for a large AHU

Snow Drift for a large AHU

Snow Drift for a large AHU

(OP)
I understand that ASCE 7-05 requires using the "windward" 0.75Hd snow drift against a roof projection 15' or longer. What about the opposite side of the AHU? Should you evalute the loading with 0.75Hd drifts occurring on both sides of the AHU at the SAME time?

The reference is section 7.8. The Figure 7-7 is not refered to in section 7.8. But it shows windward and leeward drifts occurring at "steps".

 

RE: Snow Drift for a large AHU

The way I am interpreting to section 7.8 is that the drift loads need to be applied, simultaneously, to all sides that are 15' or greater.

I believe that the intent is to say that the wind will come from any direction and deposit the snow on all sides, however, due to the 15' width dimension, the snow on the leeward side will be shielded and not be removed by the wind coming from the opposite direction.

RE: Snow Drift for a large AHU

(OP)
CNCLLC
If I understand your post, you are saying that there are potential windward drifts being accumulated on each side. One day the wind blows snow from the west and the next day it blows from the east. Is this what you meant?

RE: Snow Drift for a large AHU

When I do snow drift calculations for AHU's, I'll develop four load scenarios (one for each direction of the wind), and dump all four into Ram Steel.  Each seperate scenario will have a windward and leeward componenet.   

RE: Snow Drift for a large AHU

If it is possible and conceivable for snow to drift on all sides with L >15', then you have to design for that case, as being the worst load case.

RE: Snow Drift for a large AHU

(OP)
Assuming that only the North and South sides are >15' and the distance from the far edge of the roof to the AHU is 350' and 30' respectively, would you compute different windward drifts (0.75hd) based on the different upwind distances and apply these loads simultaneously.

I am trying to justify placing an AHU on an existing roof if I can.

RE: Snow Drift for a large AHU

SteveGregory,

What you are proposing is how I would do it.

DaveAtkins

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