Circular Slab Design

[FiniteElemet]

Hi,

I am looking for reference book which explains the design of circular concrete slab supported on columns. Somehow I am having difficulty finding a reference with good design example using ACI 318.

I have max moment (both positive and negative) for applied loads on the slab. My understanding is if I provide rectangular grid reinforcement meeting these moments, do I have to worry about providing circferential and radial bars. I am looking for info on how to design circum. And radials.

Leads appreciated,,, thanks

 

[ishvaaag]

You can do certainly the reinforcement with orthogonal meshes.

I have taken advantage hundreds of times of meshes showing identical capacity in orthogonal directions to reinforce zones of maximum moments around columns, both in elevated slabs and foundations to a total success. I tricked (to some cost) the Wood-Armer equation's need by starting from principal tensile stresses in the concrete -that interestingly show to be quite uniform at those places- to derive moments for design. Make the mesh of equal capacities able to meet such moment and you are done. Of course where your Mx and My for reinforcement are very different this result in some extra cost but I have found no one that has blinked to the practice; this very likely due to the simplicity of the plans. In your case, the plan being circular, a rim embedded beam is near mandatory.

 

[JStephen]

For circular foundations, the more common method is to use orthogonal reinforcing, otherwise, you have problems at the center with all the radial bars being in the same place. If there's a sizable hole at the center, then the radial + circumferential works out a lot better.