Determining Vf, one-way slab shear
Determining Vf, one-way slab shear
(OP)
I'm hoping someone can help me with this. The attached drawing will help get your mind around my situation.
I'm designing the base of a fix-free column (moment connection via base-plate on the existing slab).
Because I have a large moment acting on the base-plate, I am concerned with failure of one-way shear in the existing concrete slab. I am testing that the shear resistance of the concrete (Vc) against the one way shear acting on the slab (Vf), (ie: Vc needs to be > Vf). I know that the one way shear plane is located at d/2 from the edge of the baseplate.
Question is: How do I find what Vf is? Do I take some specified tributary area (as outlined by the outermost dashed line on my graphic), before calculating my stress distribution, just as I would when designing a spread footing? What do you think?
The small issues always take the most amount of time...
Thanks,
Carl, ing. jr.
Montreal, QC
I'm designing the base of a fix-free column (moment connection via base-plate on the existing slab).
Because I have a large moment acting on the base-plate, I am concerned with failure of one-way shear in the existing concrete slab. I am testing that the shear resistance of the concrete (Vc) against the one way shear acting on the slab (Vf), (ie: Vc needs to be > Vf). I know that the one way shear plane is located at d/2 from the edge of the baseplate.
Question is: How do I find what Vf is? Do I take some specified tributary area (as outlined by the outermost dashed line on my graphic), before calculating my stress distribution, just as I would when designing a spread footing? What do you think?
The small issues always take the most amount of time...
Thanks,
Carl, ing. jr.
Montreal, QC






RE: Determining Vf, one-way slab shear
RE: Determining Vf, one-way slab shear
(I am assuming d = 100mm as I am being conservative and don't have the drawings of the existing slab available.)
I am using d/2 as the critical shear section because clause 13.3.3.1 of A23.3-04 (the concrete design handbook produced by the cement association of Canada) states:
"The critical section for two-way action shall be a section perpendicular to the plane of the slab and located so that its perimeter, bo, is a minimum, but the section need not approach closer than d/2 to the perimeter of the concentrated load or reaction area."
RE: Determining Vf, one-way slab shear
RE: Determining Vf, one-way slab shear
This being the case, would it make sense to use the highest pressure of my pressure distribution for the entire affected area, then simply test two way shear?
RE: Determining Vf, one-way slab shear
RE: Determining Vf, one-way slab shear
If instead, you are simply analyzing an existing slab, the provisions of your code should tell you what to check. Different codes take a somewhat different approach, and I am not familiar with Canadian practice in this regard.
RE: Determining Vf, one-way slab shear
This isn't a research project, this is a 11ton monorail frame set in an industrial plant.
RE: Determining Vf, one-way slab shear
RE: Determining Vf, one-way slab shear
Yes, You do have to check for 1way shear also (clause 13.4.2)for which 13.4.6 refers you back to the beam shear clauses.
I do not see the confusion.