ACI dowel action in shear transfer

[7788_011]

In ACI 318-11 commentary, I have found the following in regard to dowel action in shear transfer, which is removed from ACI 318-19, in addition to shear friction.
However, I am not getting why dowel action is expressed as AcK1 which has nothing to do with dowel bars? (I don't have reference 11.45 & 11.46. Can anyone please explain)?

 

[le99]

The nominal shear friction capacity consists of two parts - the strength of the steel and the concrete friction capacity, which is only available when the two sliding planes are tightly jammed together through the dowel action (tension on steel turns compression on the concrete).

 

[7788_011]

I believe shear friction and dowel action are two different things. (I am not talking about the shear friction here). My point being dowel action should have to do with the flexural & shear capacity of dowel bars, not just concrete compression, as is expressed AcK1 in the above expression.

 

[7788_011]

Also, it says "These values of K1 apply to both monolithically cast concrete and to concrete cast against hardened concrete with a rough surface, as defined in 11.6.9."

I wonder why dowel action has to do with the roughness of interface?

 

[cooperDBM]

ACI318-19 just refers you to the Handbook for further discussion of alternate models. I believe AcK1 was a catch-all term for modes of shear resistance, other than friction, on the interface (Ac) such as mechanical interlock, dowel action, and maybe cohesion. K1 was an empirically derived shear stress resistance which is not specific to dowel action.

 

[le99]

Hope this picture helps.

 

[7788_011]

You are right. But I fail to see what K1Ac has to do with dowel action, although it is not specific to it. It seems to me that K1Ac is for cohesion only.

@le99, your first image is how I understand dowel action, which means the shear resistance should have dowel bar flexural & shear capacity involved in addition to concrete strength.

 

[hokie66]

I doubt that anyone really understands how shear friction theory relates to reality. It was apparently developed using experimental data, and an equation was invented which seemed to fit the data. So don't expect logic, statically speaking.