×
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

Unbalanced moment in punching design (Eurocode 2)

Unbalanced moment in punching design (Eurocode 2)

Unbalanced moment in punching design (Eurocode 2)

(OP)
Hi everyone!

I have a basic question. When you design a slab-column joint for punching shear in Eurocode 2, in the equation of the factor betta:

- should MEd (the unbalanced moment) be calculated using an elastic linear analysis?

Never mind seismic actions at this moment, let's assume that eccentricity is due to building geometry only. How would you support your answer?

RE: Unbalanced moment in punching design (Eurocode 2)

There are a couple of ways to take your question:
1) Analysis of the overall structure.
2) Taking the Med and converting it to stresses at the punching shear plane.

I can't respond specifically about Eurocode off the top of my head. But, for the US / ACI codes you would generally use an Elastic analysis with geometric non-linearity (i.e. P-Delta).

For calculating the stress at the punching shear perimeter this would calculated using an elastic stress distribution.

RE: Unbalanced moment in punching design (Eurocode 2)

(OP)
Thank you JoshPlum for your answer.

Actually, my question is specifically related to Eurocode. In Eurocode you calculate the resisting shear stress and the acting shear stress. In the latter calculation, you consider linear distribution of stresses due to unbalanced moment along the critical perimeter (that's the code). A factor β (beta) is introduced in the calculations as a function of MEd and VEd amongst others. My question is specific for the MEd in the formula for β (beta).

RE: Unbalanced moment in punching design (Eurocode 2)

Ved and Med are the applied shear force and moment on the column connection. And Eurocode allows Linear Elastic Analysis to be used for the analysis, so a very basic answer would be "Yes"!

RE: Unbalanced moment in punching design (Eurocode 2)

(OP)
Thanks rapt,

that's what I think too.

But when you get into more details (I mean, scientific details), you see that there is room for discussion in this topic.

RE: Unbalanced moment in punching design (Eurocode 2)

I'd surely use the elastic moments, especially for collapse hierarchy. When cracking and moment redistribution kicks in, the slab should better be able to still have a large punching capacity reserve to avoid sudden failures.

RE: Unbalanced moment in punching design (Eurocode 2)

(OP)
Thanks avscorreia,
that's logical for design purposes. However, I have been trying to find out what is the background of the Eurocode formulas for punching. So far I have not succeeded.

That would be a new topic, but if any of you have such information, I would appreciate it if you post it here.

RE: Unbalanced moment in punching design (Eurocode 2)

You're welcome. Always glad to help and learn some more in the process.

You can take a look the following document, which has extensive background on the Eurocode provisions (Punching starts at page 6-26):
Commentary to Eurocode 2

LinkStudPSR also has a great guide on the calculation of punching shear reinforcement:
Downloads
Direct link for LinkStudPSRDesignManualtoEC2v3.0

If you can read French, I'd recommend the Eyrolles books ("Calcul des structures en béton" or "Maîtrise de l'Eurocode 2").

RE: Unbalanced moment in punching design (Eurocode 2)

There is a difference between scientific discussion and what the code asks for.

Codes in may cases are simplified solutions simply because either there is no practical "scientific" solution or because the scientific solution is too complex and a lower bound solution is adequate, or because in this case in my opinion it is a brittle failure criterion and the elastic case will actually cause the failure. Redistribution due to cracking etc cannot be allowed for in a brittle failure case.

RE: Unbalanced moment in punching design (Eurocode 2)

(OP)
Thank you,
especially avscorreia for the great links. I had previously "seen" the commentary to Eurocode 2 (quite some time ago) but you reminded me of a good source of information on the background of EC.
I can read French, so I will also check the books you suggested (if I find them).

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