Precast Beam Beam to Column Connection 2

[BONILL]

Please see attached typical detail below.

My question is the following.

Is the idea in terms of the support of the beam, for its bearing area to be that of the precast beam supported on the corbel, or is the corbel just to support the beam until the cast-in-place closure is poured?

If that is the case is the reaction from the beam considered centered in the column because of a compression strut or is it through shear friction between the precast beam and the cast-in-place pour?

 

[hokie66]

That type connection uses the corbels just for erection of the precast, as stated on the detail. The finished structure has continuity of both the beam and column, so behaves just like a cast in place structure.

 

[JAE]

That's what I would say too. The corbels look too small to be full-load capacity corbels. And the reinforcement and full section going through the joint is a big clue.

 

[BONILL]

Those are my thoughts as well. The corbel would only be used for erection purposes.

But still, I'm still wondering about the cold joint between the precast beam and the pour. Is shear friction along that surface worth checking?

 

[csd72]

Agree with above, corbels are just for erection.

You will find that the sloped portion of the beam end is there to generate a compression strut for shear transfer.

 

[BAretired]

I have never used that detail. I do not care for the 45 degree slope on each beam. Looks like they would want to separate from the column.

BA

 

[gobsmacked]

Much depends on how fast the construction is. Once the beam is in place, exerting its dead load on the corbel, additional load will be transferred through the corbel until until the insitu connection has gained some strength. Otherwise, there can be no shear transfer on the vertical and sloping faces until the corbel has moved a bit vertically. I hope the corbel is reinforced with a horizontal hoop, not a vertical one.

 

[BONILL]

What if instead of a 45 degree slope I had the vertical and horizontal surfaces orthogonal to one another (90 degrees), I other words a little square blockout?
Another question. How would I go about determining how much of the reaction is transfered in shear to the cast-in-place pour and ultimately to the column, how much is transferred through the compression strut, and how much is transferred to the corbel?

Thanks for all your replies.

 

[hokie66]

A square blockout in what? The end of the precast beam?

The detail shown is just a concept, and our comments have been in relation to the way it is drawn. If it is to scale, then I wouldn't allow for any contribution by the tiny corbels (in the finished structure). You would have to consider this detail in relation to what happens in the other direction. As shown, it looks like this is just a beam and column connection, but the top slab doesn't look thick enough to span far, so is this a beam and joist system?

 

[BONILL]

Sorry I haven't been very clear.

This is what I mean.

 

[BAretired]

It could work, but the scale seems wrong. It would be better to build an adequate corbel instead of an erection corbel, then let the beam bear on it without a blockout. Corbels and blockouts are expensive to form and to reinforce.

BA