×
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 Portal
3

Concrete Portal

Concrete Portal

(OP)
Attached is an elevation of a concrete portal and I'm looking for information about the development and anchorage of the bottom reinforcing steel and where others would consider the 'beginning' of the support.  In Canada, our code requires the span to be considered as the clear distance plus the minimum of (the depth of the member or the width of the support).  Our CSA Code is similar to the ACI... Bar sizes are 35M (Similar to a #11 bar...

RE: Concrete Portal

(OP)
Thanks for the paper... Column (bunch of 25M's - #8) and bottom rfg (10 - 35M #11) were going to be straight bars; there is no chance for stress reversal.  Top reinforcing is a standard hook (35M's)  There are actually two beams side by side.  No seismic issues...

The concern I have is the splicing of the reinforcing and cut-off locations (bars in this locale are 59' and 5 - 35M fit snugly in one layer with no provision for bundling).  I'm looking for a rationalisation for commencing the 'start' of embedment length at or near the forward edge of the haunch.

The actual design moments are predicated on a span centre to centre of column and not the clear span at the haunch plus the depth of the beam.

Dik

RE: Concrete Portal

I'm not sure that you need a "rationalization" for the start of development length.  Where else would it start if not the inside edge of the haunch?

BA

RE: Concrete Portal

I'm in a world on confusion, if there is no opening moment on the joint, then why do the bottom bars need to be developed? Is this is a simple dead + live load situation? If so wouldn't you need top steel at the knee position?

While I don't understand what is going on, the way to design this joint in my opinion is to use the strut tie method (the Canadian code is the best for the strut tie in my opinion).  using this method you will get nodes, which you must develop your steel past.  

An expert is a man who has made all the mistakes which can be made in a very narrow field

RE: Concrete Portal

(OP)
Very high shear loads involved... 15M (#5) dble bars at 12...  Our concrete code has a requirement that the bars be developed a distance beyond the support to accommodate the shear and moment.

Dik

RE: Concrete Portal

(OP)
BAR...
forgot to add that I would normally use the inside edge of the haunch as the starting point with the span length equal to the clear haunch distance plus the depth of the beam at each end.

I'm trying to avoid splicing the 35M bars due to the limited length of 59' and cut-off points I can use.  The loads are 'real' and high and I'm looking for some background on the approach.  I can find no reference material on haunches and the effect they have on reinforcing steel at their location.  I want to avoid 'adding' an additional 4' or so to the bot rfg.

Dik

RE: Concrete Portal

sorry dik, I'm still not following the grove train. I don't understand the "support" statement? The area we are discussing is a joint is it not? Thus the requirement for development of the steel at the support should be for tension steel and compression steel. Is the reo being used as compression reo or tension reo? For both of these situations you should develop past the nodal point of a strut tie model.

An expert is a man who has made all the mistakes which can be made in a very narrow field

RE: Concrete Portal

(OP)
Not a joint... but the extension of the bottom reinforcing steel across the interior point of the haunch.  I suspect the contractor would create a pour joint at the U/S of the beam and that the entire beam would be poured monolithically.

Dik

RE: Concrete Portal

For the purposes outlined by dik, and in the absence of clear code language, I would use about half way across the haunch as the face of the support.  

RE: Concrete Portal

dik,

It sounds like you need to improve your understanding of the fundamentals behind the code clauses. Once you understand this then the answers to questions like this fall into place.

This is what code commentaries were invented for.

As engineers we don't just need to know, we need to understand.

RE: Concrete Portal

(OP)
csd72... that's my problem; I have a vague understanding of the principles behind it <G>... and was uncomfortable with the application of the code directly and was wondering if anyone had a better grip on things... Hokie's idea, being somewhat arbitrary, has a better comfort level, in the absence of added info.

Dik

RE: Concrete Portal

(OP)
Thanks csd... good link and some interesting ppt dox...

Dik

RE: Concrete Portal

Happy to help if you have any more specific questions once you have looked at those.

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