RISA Foundation: Footing vs. Pedestal and Mat 1

[bootlegend]

I've just started using RISA Foundation. I have a couple questions that I'm hoping someone can help me with.

1) What is the tradeoff of modeling a simple square spread footing using the "footing" method versus modeling it using the "slab" and "pedestal" options? Is the footing command supposed to be streamlined for spread footers only?

2) Using the footing design, is there a way to specify max rebar spacing in the pad? I see the option for slabs, etc, but not for the footings.

 

[JoshPlumSE]

Yes, the footing option is supposed to be streamlined for single column spread footings. It also has an optimization loop to come up with the most efficient size for the footing based on applied loading.

If you use a small mat foundation then you have a lot more flexibility. You can have multiple pedestals, non-rectangular geometry, pile supports, et cetera. But, if you decide to re-size the foundation then it is a good bit more work than it would be with the individual spread footing option.

Also, you don't have as much control over the reinforcement for individual Footings as you have for mat slabs. It's a lot more automated. You select the top and bottom bar sizes then the program optimizes the bar placement for required strength, code minimums and temp/shrinkage.... This used to mean that it could come up with some odd spacing (#6@10.327" min). Though we have corrected that so that it always rounds down to the nearest inch (or 10mm when using metric units).