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!

*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.

Jobs

Justifying Shear Wall at upper level of Condo - help please!

Justifying Shear Wall at upper level of Condo - help please!

(OP)
SEE ATTACHED IMAGE FOR CLARIFICATION BELOW.

Got a client with a condo on the 5th floor (top floor) of a low-rise. His unit has high ceilings and a lofted space that creates a "sixth story" whereby this added ceiling space projects above the rest of the main roof, almost like an additional story, but only accessible from within his unit on the 5th floor via stairs and it is very small compared to the rest of the roof. Most units have this feature.

Client wants to put a window in this upper story wall (above the main roof line) to let light in. Gravity is OK, but building dept wants us to check shear due to the reduction in SW length for this upper structure.

Anyone have a quick strategy for tackling this given this is atop a condo building with a very large footprint (upper structure us very small, relative)? I've never justified shear in a large condo where I'm not really looking into tackling the loads of the entire building unless I must.

SKETCH:

RE: Justifying Shear Wall at upper level of Condo - help please!

Does the roof of the building consist of one unbroken diaphragm? Seismic zone?
If it is a very big building and you can show that the reduction in the roof shear capacity is very minimal (2% or so) then likely it is fine. Other things to consider:

-Are there hold downs on this wall? (the opening would effectively split it into 2 short walls with much more overturning at each end)
-Is the nailing pattern heavy, are the walls blocked?
-Is this an end wall, or a wall that takes a definitive tributary load, or is it a repetitive wall with many similar types to take up the few percent that this one would fail to support in this case?

RE: Justifying Shear Wall at upper level of Condo - help please!

This doesn't appear to be very distinctive to me. (I could be wrong but...)
Once the shear load gets into the 5th floor roof diaphragm, the rest of the building will not know that there new window up at the penthouse level.
Seems like this can be addressed as a "local" condition i.e. get the load around the new opening and into the 5th floor ceiling diaphragm and that should be all.
Presumably, the original wall construction did that adequately. A perforated shearwall approach looks appropriate now. Might need some tension strap reinforcing around the new opening as I would not expect the original nailing to have been so redundant that it can be relied on for that without some augmentation.

RE: Justifying Shear Wall at upper level of Condo - help please!

The window only effects the shear wall at the upper story, not any of the stories below. You can treat it as a perforated shear wall if you wanted more favorable results. Based on your sketch, assuming the window opening is reasonable (at least 4 ft. of wall on each side), I doubt you will have an issue.

www.idecharlotte.com

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


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