Continuous Footing Design at Tilt wall Panel Jambs

[steeledan]

I'm designing a tiltwall bldg that is essentially swiss cheese - tons of opngs in most all of the panels. In looking at the continuous footing design under the panels, is it fair to ignore the opngs and calc required allowable bearing based on a solid wall w/ whatever other gravity lds are framing in on a per ft basis? Or do I have to look at each individual panel jamb (already did for the actual jamb design...) and figure out the reaction at the base of the jamb, divide it over the jamb length and provide a ftg for that load? If it's the latter, it means really wide spread ftgs at every jamb, which doesn't seem normal.

 

[a2mfk]

We normally do the latter, but keep a continuous strip footing that is widened at the panel legs to form small spread footings. You can assume some load sharing and we allow the continuous footing bars to replace spread footing bars vis-a-vis. This seems to be pretty constructable as well.

It may be more economical in your case to eliminate portions or all of the strip footing at the openings, but if the openings are overhead doors and you may have truck or forklift traffic, I like keeping some type of reduced-width continuous footing there anyway to support the thickened edge of the slab. Some combination of these may suit your situation the best...

 

[ron9876]

When possible I use a continuous footing desiged to span the opening. Which is to say both negative and positive moment. Easier and cheaper to build.

 

[ATSE]

I believe there are two distinct questions here.
1. Size and continuity of foundation.
2. Method of analysis.
If you analyze the footing as if the wall is continuous, this is simple inverted T one-way footing analysis, trivial for longitudinal reinforcing. However, you will miss the large negative moments along the footing.
Use your favorite analysis program (RISA, SAP...) and run a continuous beam on soil springs (bound this high and low) with concentrated loads at the jambs.
You might get hammer heads below the jambs.

 

[hokie66]

steeledan,
Welcome to the site. I gave an answer in another forum. In accordance with site protocol, please avoid double posting in the future.

 

[csd72]

I agree with ron, I would use the same method.

Check the worst case and see if it works without widening/undue reinforcement.

 

[structuresguy]

Yep, I agree with Ron as well. We typically check this condition as beam on elastic foundation, and design for +/- bending. However, I have done other buildings where the openings were very wide arches (20 ft or so clear), repeated at 25 ft spacing, so that you only had about 5 feet of panel leg between each 20 ft wide opening. Here I designed individual spread footings for each leg, with nothing in between except thickened slab edge. But we had no heavy loading on the slab, as it was just a restaurant.

 

[ron9876]

Did a large parking garage one time with columns at about 15'c/c (south Florida system) and used a heavy continuous footing. Contractor loved it.