concrete bean-girder connection consideration

[hssbrian]

Hello everyone, not trying to get too technical on this matter. I have an existing 10cm concrete slab with some columns located at the footings. This is an open-air structure.
The columns have some minor roof loads (no special snow or wind loads) and the slab does not have any special traffic (typical live load). I am interested in knowing if there is any special consideration needed for the beam-girder connection (see red box in the attached document). If you have any suggestions, reference or connection details it would help.

I personally don't think there should be any issues and consider that if I have enough development length it should be fine. All beams/girders are 30x30 (plenty for what is needed)

http://files.engineering.com/getfil...bbb419afb&file=Screenshot_20160815-092759.png

Much appreciate all your comments,

HSSBRIAN

 

[KootK]

Hello everyone, not trying to get too technical on this matter.

Boy did you come to the wrong place. Are we talking about a 10cm slab on grade and some grade beams? Or a 10cm suspended slab and suspended beams? Are all portions of the structure existing or are some new?

(no special snow or wind loads

What is the primary lateral system for the structure? Shear walls not shown in your plan sketch?

I personally don't think there should be any issues and consider that if I have enough development length it should be fine.

Development with a hooked bar extended to the far side of the girder is generally sufficient and what most designers do. That said, without getting "too technical", if you've designed the supported beam to have negative moment at the girder support then it's a moment connection joint and it needs to be able to transmit the applied forces including moment in the beam that would become torsion in the girder.

Usually, at beam to girder connections, the tricky bit is the need for hanger reinforcement in the girder. See the snippet below for additional detail.

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.

 

[PUEngineer]

KootK,

I was hoping there would be some follow-up on this, because I don't believe the hanger reinforcing in the girder to be a global philosophy. At least I'm unaware of any requirement, prescriptive or otherwise, for it in the ACI codes.

Are you in Australia or do you apply that to work in the US? Doing a google search for 'detailing of beams ctd', pulls up a PDF of a presentation. Are there code requirements for this?

 

[KootK]

- I'm in Canada and we have code provisions for hanger steel.
- As you noted, the document that I posted is Australian, they have code provisions for hanger steel.
- In my opinion, irrespective of code provisions, statics/logic indicates a need for hanger steel.
- ACI 318 does not have explicit hanger steel recommendations but ACI352 does (Recommendations for Design of Beam-Column Connections...)

It's basically the same provision in all of the codes.

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.

 

[KootK]

For what it's worth, I worked in the US for a decade and I know that it's quite common to omit/overlook the beam hanger reinforcement in US practice. I did a lot of that myself and, to my knowledge, nothing went awry.

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.

 

[rapt]

Agree entirely KootK.

Just because the code does not specifically say it does not absolve the designer of any responsibility. It is logically required. There are too many code lawyers out there these days trying to find holes they can exploit in codes. The code is a set of limits and allowed simplifications, not a design text book and it should never be read as one.

ACI does assume that the load is applied at the top of the member for its shear design. If it is applied anywhere else it must be raised to the top before normal shear rules are applicable.