×
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

2-way slab punching shear at edge columns

2-way slab punching shear at edge columns

2-way slab punching shear at edge columns

(OP)
I have a 2-way slab and am checking punching shear at the edge columns. The critical section at an edge column typically has 3 sides. How far past the edge face of the column must the slab cantilever before I can consider the punching shear critical section to wrap around all 4 sides of the column? (I can't find anything definitive in ACI 318 nor in the PCA notes that clarifies this.)

RE: 2-way slab punching shear at edge columns

Can you check it both ways to see what governs? 3 side critical section, with two of those sides extended to the free edge, vs a 4 sided section?

I'd imagine it may be a case-by-case decision (informed by experience and maybe a helpful rule of thumb from one of our wiser members).

RE: 2-way slab punching shear at edge columns

Yes, you check it both ways and the worst case (shortest perimeter) governs.

RE: 2-way slab punching shear at edge columns

Quote (cliff234)

How far past the edge face of the column must the slab cantilever before I can consider the punching shear critical section to wrap around all 4 sides of the column?

Some countries have code recommendations for this and some don't. I believe that Canada and Europe both have (or had) recommendations of five times the slab thickness beyond the column face. That said, rapt's method strikes me as eminently rational.

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: 2-way slab punching shear at edge columns

Its definitely an 'engineering judgement' kind of thing. I actually had a brief session about how ADAPT handles it, and if I recall correctly the program checks for 8*slab thickness from the edge to determine if it is a corner, edge, or interior column.

RE: 2-way slab punching shear at edge columns

There's this from ACI 351.2-89. I'll try to dig up the 2011 version.

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: 2-way slab punching shear at edge columns

ACI 318 11.11.1.2 and the commentary make it reasonably clear that the designer needs to find the controlling punching section.

RAM Concept which I've used and ADAPT etc will do this as long as the programs are given proper inputs.

If you're hand-calcing, you need to run it a few ways. Consider not merely the perimeter lengths but also the slab-column moment (ACI 318 Fig R11.11.7.2), which will be somewhat increased by increasing cantilever distance. If you have a lot of conditions, a spreadsheet will be useful. Plus architects are known to shift slab edge dimensions.

RE: 2-way slab punching shear at edge columns

It did change with the 2011 version of ACI 352.1 - Guide for Design of Slab-Column Connections in Monolithic Concrete Structures.

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: 2-way slab punching shear at edge columns

(OP)
Wow. Thanks for all of the responses. You answered my question.

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