×
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

drag force on rigid diaphragm

drag force on rigid diaphragm

drag force on rigid diaphragm

(OP)
I am working on a single story masonry building with concrete roof(see attached sketch) . I am wondering do I need to consider drag force when design the roof (e.g. for wall 3).  

RE: drag force on rigid diaphragm

You have nothing to drag. Distribute the horizontal load and corresponding torsion on the bearing walls (ignore partitions) per wall rigidity. Do it for each direction.

RE: drag force on rigid diaphragm

Yes, but if the interior walls are similar in construction to the exterior walls, and they are also attached to the roof, then they will collect lateral forces.

If the force transferred from the diaphragm to the Wall 3 can be connected within the length of Wall 3, then technically a collector/drag strut isn't needed.  I might add additional reinforcing in the roof diaphragm along wall 3 just in case.

 

RE: drag force on rigid diaphragm

The reason to ignore the partition walls is because there lies high possibility the interior space would be altered in the future, thus create difficulty by then. Yes, the ignored walls inevitably will share the loads, but the method is conservative, shouldn't have much impact on their's strength and performance.

RE: drag force on rigid diaphragm

"Yes, the ignored walls inevitably will share the loads"

It is true and must be accounted for in design unless a means to prevent force transfer to these walls is made.

RE: drag force on rigid diaphragm

"It is true and must be accounted for in design unless a means to prevent force transfer to these walls is made."

If you don't make such provision (for partitions - non bearing) in your design, the trouble is down the road. The wall colud be removed entirely without replacement for space recongiguration/re-utilization purposes . Now which member is to carry the add'l load after the removal? How you do retrofit under concrete roof (not impossible, but costly)?

Distingusish the terms - BEARING vs PARTITION (non-bearing, intend for removal).

RE: drag force on rigid diaphragm

One more noe:

Not all interior walls are automatically labelled "partitions", it is up to your design. So, it's good practice to label the bearing walls on the drawings.

RE: drag force on rigid diaphragm

(OP)
the reason I use wall 3 and 4 as shear wall is because wall 2 and wall 6 have too much openings and wall 3 and wall 4 are solid.

JAE, if I add additional rebars for drag force, where should I add them, just the stripe of the roof aligned with wall 3 or 4 with the width of the wall? Do I need add stir up since the drag force could be compression?

RE: drag force on rigid diaphragm

I would add them to either side of the opening and extend them parallel to wall 3 for at least half the wall length.  No need to curve them into wall 3 itself - just get them into the area of the diaphragm to either side of wall 3.  The slab will do the rest.

Mike McCann
MMC Engineering

RE: drag force on rigid diaphragm

What Mike said....

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