Slab-On-Grade Supporting Cantilever Column/Wall

[guanorican]

I have a project where I'm adding some cantilever columns anchored to and existing slab on grade to brace some free standing walls. How can I justify the adequacy of the connection to the slab on grade? Since the slab on grade only has reinforcement for temperature and shrinkage (assuming wire mesh), from a design stand point I'm considering it as plain concrete. I need to make sure the existing slab on grade can take the moment generated from the cantilever column. My thought was to consider a tributary area of the slab as a "footing" and calculate the tensile stresses in the slab and check that vs the modulus of rupture of concrete. If my stresses are less than the modulus of rupture than i'm safe... Your thoughts?

 

[hokie66]

My thought...you should think again. A slab on grade is not supposed to take bending of this type.

 

[JAE]

Not sure how you can have a reasonable capacity on a slab-on-grade in bending. Yes you can determine the maximum "plain concrete" moment but it would be an abrupt form of failure which, with a wall of wall of 7 feet or more I'd worry about public safety.

Alternatively, if the wall had all sorts of turns and corners where it was self bracing and the slab only took vertical gravity loads, perhaps then I'd do it.

 

[BAretired]

I agree with the above...don't expect a slab on grade to support a cantilever column.

BA

 

[guanorican]

Thank you for your response... I wasn't clear on my previous post on the location and material of the wall. This are interior (5psf lateral load) gyp partition walls 8' to 10' tall inside a warehouse with no ceilings. I will look into adding some returns to self brace the wall. Thanks again!

 

[hokie66]

Assuming you can't provide the required corners, a common approach is to extend vertical wind braces to the roof structure, possibly square hollow sections.

 

[guanorican]

Thank you for your response Hokie66. Yeah we are doing this at other areas of the project to brace some IMP walls. I was just trying to figure out the feasibility of this other approach given the low moments generated. Even if I used the aforementioned assumptions it ended up being very hard to make it work. I will end up using full height wind columns or adding some returns. Thanks to all…