Concrete Floor/Roof Slab - Structural Member & Baseplate with Overturning

[TPower7]

Hi all,

This question is more general than specific.

I have a structural member that has an applied horizontal load. The structural member is welded to a base plate and the base plate is connected to the concrete slab with anchor bolts.

If we assume that all anchor bolt checks are fine (and structural member/base plate checks), what failure modes are required for checking the floor/roof slab?

I have sketched the force couple applied to the slab below:

Thanks,

 

[phamENG]

Follow the load path. What does the reaction do to the slab? It's going to introduce some amount of shear and moment. Draw your shear and moment diagrams with this loading and see what they look like compared to the capacities along the length. Review ACI 318 and a good concrete text book for the various types of shear and moment checks based on the configuration of the slab. It will vary based on support configurations, 1-way vs. 2-way, etc. There are methods out there for simplification of one way slabs for point loads all the way up to finite element checks of slabs that can be done.

 

[RPMG]

The first check should be concrete breakout failures, generally done with a program like hilti profis. Also, the plate is a moment end plate and the slabs have to have the flexural capacity

 

[Celt83]

Review ACI 318, AISC Design Guide 1 or Design of Welded Structures by Blodgett

also barring any special detailing that would force the anchors to act in compression the force diagram is not as you have it shown and instead you will develop a resisting compression block at the plate/concrete interface, Design Guide 1 and Blodgett have canned formulas for this with uni-axial bending.

My Personal Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

Open Source Structural GitHub Group:

https://github.com/open-struct-engineer

 

[phamENG]

Good catch on that, Celt.

But, to refocus the discussion, let's look at this quote from the OP:

If we assume that all anchor bolt checks are fine (and structural member/base plate checks), what failure modes are required for checking the floor/roof slab?

You guys are referring to steel design guides and standards, but they're looking for concrete checks.

 

[TPower7]

Thank you for the replies. phamENG you are correct, we are more focused on looking at the concrete slab checks (excluding anchor bolt failure checks, these are assumed to be fine).

If we had a situation where there is an existing one-way slab and the structural member was loaded in the the long direction (see below).

Would the one-way checks suffice?

 

[Celt83]

Concrete Checks would be:

Flexure
One-Way Shear
Localized two-way punching shear at the plate perimeter
Localized bearing at the plate ie sigma,c in my sketch needs to be less than the allowable bearing stress
Deflection should also be checked

If this happens to be a Post-Tensioned member you'll also need to satisfy the cross-section stress checks outline in the code.

My Personal Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

Open Source Structural GitHub Group:

https://github.com/open-struct-engineer