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

Transfer Slab - Shear Check

Transfer Slab - Shear Check

(OP)
Hello guys,
I have a concern regarding transfer slabs design; I have a 360m height tower which include a 4000mm thick transfer slab at intermediate level,
- While checking shear, shall I check it with normal shear check (φVc = φ x 0.17 x SQRT (f’c) x b x d) or it can be considered like a deep beam and check the corresponding shear (φVc = φ x 0.83 x SQRT (f’c) x b x d)?
- Does it make sense to check the punching shear at this kind of slabs (transfer which includes supported columns-walls and above transferred columns-walls)? Is there any risk for punching in this is case?
Thank you.

RE: Transfer Slab - Shear Check

2
Boch,

How would we know if you do not tell us the spans of the transfer slab.

Normally a transfer slab will be sized based on shear requirements, and yes punching shear could be critical.

I would not be trying to take short cuts on something like this. If it is close to a Deep Beam, I would be designing it both ways and adopting the worst case solution!

RE: Transfer Slab - Shear Check

BOCH,
Rapt has given a concise and perfect answer to your question.

RE: Transfer Slab - Shear Check

Agree with RAPT, Also agree shear requirements typically dictate the thickness.

"Structural Engineering is the Art of moulding materials we do not wholly understand into shapes we cannot precisely analyse, so as to withstand forces we cannot really assess, in such a way that the community at large has no reason to suspect the extent of our ignorance." Dr. Dykes, 1976

RE: Transfer Slab - Shear Check

(OP)
Hello guys,
Thank you for your reply.
The transfer slab span is 12000mm (span over thick is less than 4, that's why i am asking this question), this is not a matter of short cuts, i am in front of a case on which we can apply shear requirements for deep beams which is more than normal shear by 0.83/0.17 = 4.88 times! (just trying to be consistent with the code).

RE: Transfer Slab - Shear Check

The use of Strut and Tie analysis is, I believe, standard practice for design of transfer slabs with a 3/1 span/depth ratio. Beam theory is not appropriate.

Where do those 0.83 and 0.17 numbers come from?

RE: Transfer Slab - Shear Check

(OP)
These are from the metric version of ACI code, when using f'c in MPA the factor is 0.17 same like when using f'c in PSI the factor is 2.

RE: Transfer Slab - Shear Check

OK, but I still don't know where the 0.83 comes from. Is that a specific clause in the ACI code, or is it what you have derived?

RE: Transfer Slab - Shear Check

(OP)
It is stated in ACI 11.7.3 that "Vn for deep beams shall not exceed 0.83xSQRT(f'c)xbxd"

RE: Transfer Slab - Shear Check

You are mixing/confusing Vc with the upper limit for Vn imposed for deep beams. Vc is beam shear taken by concrete only, Vn is limit on total shear.

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