Slab on grade design guidance
Slab on grade design guidance
(OP)
What is a good resource for design a slab on grade subjected to a column load? I have a column with an 18kip vertical load and soil with 150 pci subgrade modulus and I'm wondering if I can use a 12" slab. Hopefully there are tables that will eliminate the need for FEA.
Of the two resources I have ACI-360 appears best suited for a grid of posts and TM 5-809-1 appears best suited for walls at the center and edge of slab.
Of the two resources I have ACI-360 appears best suited for a grid of posts and TM 5-809-1 appears best suited for walls at the center and edge of slab.






RE: Slab on grade design guidance
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Slab on grade design guidance
RE: Slab on grade design guidance
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Slab on grade design guidance
I could not find reference to this method in more recent City of L.A. Information Bulletins.
RE: Slab on grade design guidance
Is cracking of the slab considered?
Is settlement considered?
Is the load provided something more akin to a collapse load?
To get to the bottom of these questions, I spent a week digging into the bibliography and a) couldn't answer that question, and b) found that at least one of the items didn't exist (item 9).
Please also not that the paper is not appropriate to use for racking loads and this violates the spacing requirements
I`ll use the paper with a significant additional FS, or utilize more traditional methods.
RE: Slab on grade design guidance
On first glance, the loadings appear to be too high and I might consider using 1/2 the tabulated values...
Dik
RE: Slab on grade design guidance
http://www.apd.army.mil/epubs/DR_pubs/DR_a/pdf/web...
Perhaps it can serve as a reference for you.
RE: Slab on grade design guidance
http://www.steeltools.org/communities/community-ho...
It's old but still a good reference. I believe the main failure mechanism is typically rupturing of the concrete on the tension face.
RE: Slab on grade design guidance
RE: Slab on grade design guidance
The traditional methods have been used successfully for years. Someone publishes an article (again, with no mention of how they determine "failure") and suddenly we triple those loads?
For comparison, for a 4" slab:
My typical slab notes = 2.5k allowable
British TR-34 = 7.8k allowable
Ringo's slab on grade book = 5.5k allowable
This new article = 21k allowable.
My first course of action is always the traditional methods that are well established and tested.
If additional capacity is necessary, I consider cracking, settlement, etc and discuss those risks with the project manager / client.
RE: Slab on grade design guidance
Thanks, Dik
RE: Slab on grade design guidance
https://www.thenbs.com/PublicationIndex/documents/...
I`ve found comprehensive design procedures to be woefully lacking in ACI and appreciate the document. It provides guidance on how to deal with edge conditions, corner conditions, closely spaced posts, etc.
Ringo wrote a book in the 90s. I haven't seen any new or ground breaking research or information in the book, but its a great summary of the different design methodologies that are common in the states. He reviews the different methodologies (Army, PCA, WRI, ACI, etc) and provides a recommendation as to which methodology is most appropriate for a given load configuration (line load, point load, distributed load, etc).
https://books.google.com/books/about/Designing_Flo...
It was 2013 that I was getting deep into the weeds on this design aspect. If I remember correctly, the british methodology is looking at bending stresses (top and bottom) created in the slab and comparing that to the rupture strength of the concrete. They recommend permitting cracking in the bottom of the slab and limited your flexural stresses in the top of the concrete.
I think Ringo is just a summary of the traditional concrete design methodologies.
RE: Slab on grade design guidance
RE: Slab on grade design guidance