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


Drag truss/diaphragm design?

Drag truss/diaphragm design?

Drag truss/diaphragm design?

2-story building.
Wind controlled design.
Shearwall located under drag truss.

Is it necessary to design the drag truss to transfer the roof wind loads (wind loading on roof only) OR does it need to transfer the diaphragm loads (wind loading on roof + half of 2nd floor wall height)?

I know that the shearwall load at the top of the 2nd floor is the diaphragm load, but is it necessary to design my drag truss for this total load?


RE: Drag truss/diaphragm design?

Is the truss under the roof or under the floor?

RE: Drag truss/diaphragm design?

Do you have any diphragm at the truss bearing elevation?  Or is the wind load carried up the diaphragm attached to the top chord of the truss?  If it's the latter, then yes, design for the roof wind load and half the wall height.  Think of the section of wall exposed to wind between two shear walls.  Wind blows on the wall, half travels to the 2nd floor diaphragm, and half to the top of wall/truss bearing.  Since the diaphragm is on the top chord of the trusses, your collector truss has to transfer this down to the shear wall.   

RE: Drag truss/diaphragm design?

As I understand the question, the drag truss would only have to drag in the forces from the roof diaphragm to the shear wall underneath, let's call it shear wall "A", shear wall "A" being between the second floor and roof diaphragms.  

If there is a shear wall "B" below shear wall "A", then that shear wall would see roof plus second floor lateral forces, but not shear wall "A".  

Mike McCann
MMC Engineering

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!


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