Moment induced shear force in RCC connection

[RabitPete]

In a moment transfer system like on the attached detail, how do one accounts for shear force between compression and tension side of the moment arm? I am probably missing something, but it keeps bothering me. Would not a crack develop as shown due to pure moment alone? Axial gravity loads are negligible when compared to the forces due-to moment and would not require any shear reinforcement.
Moment Transfer

 

[r13]

I think this is what is happening. The stresses on the confined core are shear in nature, that produce couples to be resisted by the reinforcing and the concrete.

 

[RabitPete]

So should we check for those stresses on the confined core? I feel that simply satisfying Ldh is not enough and transverse reinforcement is necessary, but with the depth of only 14" and 3" cover on the bottom, not much room left for stirrups.
Would adding diagonal reinforcement help and to what extent and how to calculate it? Looks a little extreme of a solution. I typically see those on 1 side of a retaining wall, as moment always acts in 1 direction. In my case cantilever arm spins and moment can be applied from any side.

 

[r13]

I think your detail is fine, though I don't know how to quantify the benefit. You can also consider adding closely spaced ties in the column all the way to the bottom of the base mat, or add stirrups to a strip (embed beam) across the column. Both methods offer better confinement to the core. But watch out for congestion that will lead to poor vibration at the joint.

 

[KootK]

Would not a crack develop as shown due to pure moment alone? Axial gravity loads are negligible when compared to the forces due-to moment and would not require any shear reinforcement.

Yes, exactly so.

In a moment transfer system like on the attached detail, how do one accounts for shear force between compression and tension side of the moment arm?

1) Right or wrong, know that most folks won't do anything at all to check this.

2) As for how to check it:

a) Strut and tie. Unfortunately that's time consuming and will result in your requiring a tie which would probably be impractical as you intimated.

b) ACI has a document called Recommendations for Design of Beam-Column Joints in Monolithic Reinforced Concrete Structures. In that document, they present some pseudo-sectional stress checks for verifying shear capability within the joint. This is what we're supposed to be doing for beam-column joints and what I would be inclined to use in this situation were I to attempt a check.