Contact US

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.

Students Click Here

FRP for Sway Column to AS3600 (or any other standard)

FRP for Sway Column to AS3600 (or any other standard)

FRP for Sway Column to AS3600 (or any other standard)


Looking at a concrete flat slab sway frame (2 storey / 550 columns / 325 flat slab / 9m grid) and note that AS3600-2009 and 2018 Cl 5.6.2 is for braced columns only, it then refers you to Eurocode or other approaches.

Looking at Eurocode EN-1992-1-2, Methods A & B both say braced structures. Appendix C also says braced structures, but has some higher slenderness values that my frame (using ke=2.2 effective length) does fall into.

I thought i would look at NZ codes as I understand concrete frames are more common across there, and NZ3101-2006 is silent on braced/un-braced when it comes to columns and fire design is left to a very simple table.

My questions are:
1) if I sit within the slenderness values of EC2 using Ke=2.2, even if they are for a braced structure, is this valid? My thinking for this is:
- the slenderness value accounts for the braced/not braced.
- When designing a column for strength via an interaction curve, sway effect is accounted for in the slenderness - ie there isnt a
seperate braced and unbraced design approach in determining the interaction curve.
2) any other suggested codes / approaches?
3) general comments?


RE: FRP for Sway Column to AS3600 (or any other standard)

The slenderness stuff in NZS3101 is based on braced columns I believe, ACI has effective length values for unbraced columns if you have access to that.

For example these are the alignment charts from ACI:-

RE: FRP for Sway Column to AS3600 (or any other standard)

Eurocode EN-1992-1-2 with Amendment 1 (released later 2019) has tables in Annex C for sway columns.

RE: FRP for Sway Column to AS3600 (or any other standard)

thanks for replies
- Agent666 these seem to give the same k values as AS3600
- RAPT perfect! i will now get a copy of A1, i was using a pre-A1 version of EC2

RE: FRP for Sway Column to AS3600 (or any other standard)

hi rapt

i have purchased BS EN 1992-1-2 with amendment 1 as per your comment - thanks for heads up. Annex C looks relatively straightforward and essentially gives a limiting slenderness based on col size / FRL / loading ratio and eccentricity.

My question is to the design a rectangular unbraced column in fire, do i only need to use annex C? Or do you still need to use either the isotherm or zone method to check moment and axial. (Annex C is so straightforward i feel i a missing something using it alone!) I accept that it has limitations such as rectangular reinforced columns of certain sizes only, whereas method A and B allow greater flexibililty.

A few things that make me think it is Annex C only are:
- 4.2.1 note 2 clearly refers to Annex C for unbraced systems.
- 5.3.1 note says Method A & B are for braced structures only


RE: FRP for Sway Column to AS3600 (or any other standard)

You are reading the same document as me. I know no more.

My understanding is that some German Universities have used the zone or isotherm strength calculation methods to determine the capacities of sway columns under fire conditions to produce the tables in Annex C. Presumably as they have investigated the effects of strength reduction from the Annex B strength reduction methods along with slenderness calculations to give the results in Annex C.

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! Already a Member? Login


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