×
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

Wind Corner Zones on Walls Theory

Wind Corner Zones on Walls Theory

Wind Corner Zones on Walls Theory

(OP)
ASCE is clear that the corner zone width 'a' is "10 percent of the least horizontal dimension or 0.4h, whichever is smaller, but not less than either 4% of least horizontal dimension or 3 ft." Working for a curtainwall company, I have to use this rule on a regular basis. But, I was asked WHY the least building width influences ALL of the corner zone dimensions, and I can't come up with a legitimate reason other than "the code says so." Does anyone know how ASCE arrived at this rule or have an intelligent theory on it? Thanks for the help.

RE: Wind Corner Zones on Walls Theory

Most of the ASCE 7 wind coefficients and rules came out of several wind tunnel tests and I would think that the "a" dimension was a result of those tests, not some theoretical analysis done on paper.

Read the commentary for Chapter 30 to get a feel for where all these came from. That's my guess anyway.

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

RE: Wind Corner Zones on Walls Theory

So, are you insinuating that this is a situation of the tail wagging the dog?

Mike McCann, PE, SE (WA)


RE: Wind Corner Zones on Walls Theory

We have similar situation with the height of the building
The wind load depends on the total height of the building
SO if you a high building the wind load is higher also for the lower bottom parts of the building

for example...designing the entrance facade at ground floor
two buildings... different wind load for the entrance facade because one of the buildings is much higher than the other one

somehow not logical.... or ?






best regards
Klaus

RE: Wind Corner Zones on Walls Theory

Actually, at least for windward pressures, you are allowed to use qz, which is the velocity pressure based on the height above ground that the component you are designing is located. There are cutouts on that in that for z <= 15' you have to use 15' minimum. For roof pressures obviously, and for leeward suction forces you use the mid-height of the roof above ground. For most structures there probably isn't enough difference between using z and h so people don't bother, but for something like an entrance canopy on a high-rise it could be significant.

RE: Wind Corner Zones on Walls Theory

(OP)
JAE, I'm not saying it's not in there, but I just looked at the ASCE Commentary and saw nothing. msquared48, you might be on to something here.

Here is an example to better illustrate my confusion: Let's say you have a 100'x30' building and a 100'x90' building. Assuming the 'h' is large enough and the same for both buildings, the corner zones will be 3' and 9' respectively, correct? It is hard to imagine WHY there would be a different corner zone width for the 100' faces of the two buildings when they are the exact same face. In my line of work, the corner zone may require additional reinforcing, fasteners, weld, etc. so this dimension is pretty important.

RE: Wind Corner Zones on Walls Theory

The commentary, in many instances, refers to the wind design data within the code as coming from experimental wind tunnel tests (i.e. research projects).

These typically would be modeled building shapes of various sizes and configurations and from those tests I speculated that the size of the building may have revealed a relationship between the higher peak corner pressures, their extent away from the corner, and the dimensions of the modeled building.

The fact that you can't "picture" this between a 30 ft. wide and 90 ft. wide building is reasonable - but my "guess" is that wind pressure behavior at corners is quite complex and not as intuitive as may be supposed.

You might try contacting Texas Tech university, or perhaps Dr. Kishor Mehta or his firm (here: http://www.depts.ttu.edu/ceweb/faculty/faculty.php...) as they/he does a lot of wind research.

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

RE: Wind Corner Zones on Walls Theory

when the wind hits the windward face of the building the only 3 routes for the air to escape are around both sides and over the top....the larger the width the more air volume is involved and thus the increased turbulance at the corners......anyway, that's my take on it..
Klaus...the leeward side of the building experiences the affects of wind blockage mentioned above...this affect(suction), I would assume is approximated by using the full height of the building...if for example, the first floor was totally open, then,IMO, one may be able to use the varying press according to hz for the leeward side....

RE: Wind Corner Zones on Walls Theory

One reason for the difference in height values is that a higher building needs to be strengthened (i.e., stiffened) in the lower stories so that drift is reduced.

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