×
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

Concrete Tilt-up Addition

Concrete Tilt-up Addition

Concrete Tilt-up Addition

(OP)
We are doing an addition to an existing 18 feet high concrete tilt-up building with a flexible roof diaphragm (See attached for layout). There is an existing re-entrant corner with its respective drag lines. Our addition consists of squaring off the building by adding to new walls.

My question is:

Is there a way to neglect the lateral resistance of the walls that make up the re-entrant corner and assume that the outer walls of the newly created box will resist the seismic loading?

RE: Concrete Tilt-up Addition

I don't think you can neglect it if it indeed is connected to the diaphragm and has stiffness. The load will always follow the stiffness.

By adding the corner, you are increasing the lateral demand on the drag lines and associated shear walls so you'd have to simply check those with the added load.

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

RE: Concrete Tilt-up Addition

By the position of the interior walls respecting the new walls, I do not think the existing drag lines would be affected, but the interior panels will. I am assuming the drag line links are at the interior corner at the existing walls.

Also, the diaphragm chord forces may or may not be impacted. Check those too.

Mike McCann, PE, SE (WA)


RE: Concrete Tilt-up Addition

(OP)
That's what I thought, I was just trying to see if I could simplify my work.

Thank you for your input.

RE: Concrete Tilt-up Addition

Is the goal to avoid having to evaluate the existing drag lines or is it to shelter them from new load that would cause overstress? If it's the former, then the only strategy that I can think of would be to install bracing against the re-entrant corner and set it up as two separate buildings. If it's the latter, there are a couple of options:

1) If you can prove that the re-entrant walls would fail in a ductile fashion, you might be able to redistribute load out to your new walls. I'd think the odds of this working out to be pretty low.

2) If the individual wall segments of the re-entrant corner are stitched together to act compositely for lateral, you could remove that stitching and thereby reduce the stiffness of those walls. Folks on site may think that you've lost it.

The proportions of the building being what they are, I wonder if you might be able to justify rigid diaphragm behavior, even with an untopped steel deck. I'd think that a rigid analysis would shift a good deal of load away from the re-entrant corner walls.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Concrete Tilt-up Addition

(OP)
KootK,

In a way I was trying to avoid both, but given the existing conditions I won't be able to take any shortcuts and I will just have to analyze the re-entrant corner and drags for the additional loads.

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