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# Corbel action on Column analysis4

## Corbel action on Column analysis

(OP)

I have a doubt that how the RC corbel action(Tie action) is applied to the RC column analysis
Is it correct to applied it as a Pxav(P- vertical action on corbel, av- distance between root of corbel & line of action) or as a Tie force which counteracting the column compressive load. Consider that the RC corbel and RC column are non precast element

thanks
Ruchira

### RE: Corbel action on Column analysis

How does the "Tie force which counteracting the column compressive load"?

### RE: Corbel action on Column analysis

(OP)
When the corbel is designed as strut and tie method, the top reinforcement of the corbel will subjected to a tie force. As this rebar is anchored to the column after passing the bend, it will counteract with the compressive load(as tie force become vertical) of a typical column(Assume that column section is fully compressed. Is this concept is right?

### RE: Corbel action on Column analysis

Load from a corbel will add to the vertical (gravity) load on the column. The corbel will also subject the column to a bending moment which is the corbel vertical load times the lever arm (the distance from the corbel load to the column centroid).

### RE: Corbel action on Column analysis

(OP)
Thanks a lot. I have confused with tie action with the bond force in concrete. The bond force around the tieing rf create a vertical load on column.
Thanks rapt and hokie

### RE: Corbel action on Column analysis

I see what you're getting at. The vertical part of the tie does exert an upwards force on the column as a result of bond stress. However, the tie also exerts a bearing stress against the concrete at the bend which has a downwards vertical component. I would argue that those two effects cancel one another out.

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.

### RE: Corbel action on Column analysis

(OP)
Cancel-out in the sense to make the tieing reinforcement in an equilibrium(newton's third law). But the bond force will exert a compression in the column. Similar phenomena will be activated in the post tension ducts also.
My point is that no moment is transferred to the column when a strut and tie is used as the forces only are axial in the truss which directly transfer the corbel vertical load to column as a compression load but no moment.

### RE: Corbel action on Column analysis

Moments don't just disappear. If you have an eccentric vertical load applied to a column then the column has a vertical load plus a moment, no matter how you analyse it.

Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/

### RE: Corbel action on Column analysis

(OP)
Got it. thanks KootK & IDS. It is basically depends on how I analyse the problem

### RE: Corbel action on Column analysis

ruchira2580:

I think you are getting 'stuck' conceptually and it may be best to think in terms of 'external' applied load/s causing 'internal' forces/stresses.

So, as IDS states, you have an "eccentric vertical load" (this is your 'external' load x eccentricity = 'externally' applied moment), and your strut and tie forces are your 'internal actions' to those external applied loads.

### RE: Corbel action on Column analysis

(OP)
Thanks Ingenuity. It explains a lot...

### RE: Corbel action on Column analysis

#### Quote (OP)

Cancel-out in the sense to make the tieing reinforcement in an equilibrium(newton's third law). But the bond force will exert a compression in the column.

Also cancel out in the sense that the net impact of the tie on column axial force is zero beyond the tie itself.

#### Quote (OP)

It is basically depends on how I analyse the problem

Any internal analysis that is complete will produce results consistent with the external results. The answer does not depend on the method.


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.

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