Widened portion of Beam - Top and Bottom Rebars To Be Developed or Not?

[e104909]

Sirs,

I have this 24 inch wide beam that needs to be widened to support a wall on top. The proposed is 8" widening on the side of 24". Attached is the detail.

I designed the 24" beam to carry all the framing forces and loadings and as far as I know the widened portion of 8" will just be there to support the wall on top.

My question is:
Do you usually have to dowel the top bar and bottom bar on the widened portion? and have it fully developed in tension?

If I follow ACI code, 6" at the bottom bar will be sufficient per typical beam details of continuous beams.

I would appreciate your comments in the attached.

 

[Tomfh]

It is common to have a ledge or corbel or similar protruding from a beam, where the ledge terminates before the column. If the ledge is strongly attached to the beam and the beam itself can carry all the forces then the extension needn’t be developed into the column support.

I have some concerns with how your extension is attached to the existing beam. It appears you are glueing your U-bars on the outside of the existing beam bars? I would be drilling your ties into the guts of the existing beam.

What are the closed ties for?

Since overall robustness is a consideration here due to post installed reo, having your extra connection back to the support could be a good idea, though not necessarily
Fully developed in tension.

 

[e104909]

Hi Tom,

Thanks for your response.

The extension is actually going to be poured with the beam. It is not existing, but it will be integrated with the beam.

I'm conservatively ignoring that extended portion in my design. Since I just want to consider the rebars that will be welded to the steel box column.

The C-shape ties are developed with Ld from the face of the beam. It will be matched with the spacing of closed ties of the beam.

 

[Tomfh]

Now I'm really confused. If the beam isn't built, why don't you simply make the beam wider? Why the U-Bar extension detail?

 

[e104909]

I am limited with the number of couplers that can be welded on the 24" steel box column. With that said, i thought of detailing it this way so that 1 single line of reinforcement will be in the middle of 8"thk widening. In actual drawing, i will specify that width to be 32".

Do you suggest just one hoop?

 

[e104909]

I guess the correct question is, what difference would it make if I have a single loop vs a c shape stirrups?

 

[HTURKAK]

the use of single loops is OK .. did you consider the torsion effect of the wall with eccentric loading?..
The sketches that you provided are not enough to get the full picture..
Consider posting the structural plan ..