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

Wind Zone analysis B and D zones?

Wind Zone analysis B and D zones?

Wind Zone analysis B and D zones?


Just had a couple of questions.

It is referring to the main wind force resisting system analysis.

My questions are:

1.)  When analyzing a structure per MWFRS some vales for the roof loads (Zones B and D) are negative values stating that it is pulling out on the roof structure instead of flowing into it.  So how do you deal with those values?  I have seen designers instead of using the negative values they simply just switch the sign to + and call it conservative.  I have also seen designers assume if zones B and D <0 than assume =0.  Does the ASCE7-05 Address this issue (where)?  And if it does and you can either assume 0 or use a positive value then why have does the ASCE7-05 even have the negative values showing, wouldn't it make sense to set them to zero or positive in the first place.

I know that the negative values are stating that they are coming out of plane therefore create a circular motion and a possible moment.  But when doing the analysis calculations I have never subtracted the negative B and D regions from the A and C when finding the shear reactions.

2.) This question is referring to another code provision.  It is specifically ASCE7-05 about minimum pressures.  What is the take on this?  I see it two different ways:
          1. That you must have 10 psf minimum on all zones A,B,C and D.  Implying that if B and D were negative or < than 10 then they would then become positive     10.??
          2. The minimum design pressures on any structure have to exceed a minimum of 10 psf for all zones based on the area Af?  And if the pressures are less than that when analyzed then 10 psf's have to be used for all the zones

thanks for everyones future help.
Replies continue below

Recommended for you

RE: Wind Zone analysis B and D zones?

Negative values of wind pressure on a roof are uplift forces and can control the design of various components, especially connections of the roof to the frame.

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


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