Corbel action on Column analysis 4

[ruchira2580]

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

 

[rapt]

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

 

[ruchira2580]

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?

 

[hokie66]

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).

 

[ruchira2580]

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

 

[KootK]

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.

 

[ruchira2580]

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.

 

[IDS]

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/

 

[ruchira2580]

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

 

[Ingenuity]

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.

 

[ruchira2580]

Thanks Ingenuity. It explains a lot...

 

[KootK]

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.

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.[pre][/pre]

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.