Looking for folks with experience evaluating steel structures that have been exposed to fire/heat. I've read some reference material/articles about general evaluation processes but its a bit of a mixed bag. Some say more or less that if it hasn't deformed than its generally ok. Others say...
Looking back at the OP's sketch, yes.......50+ feet would probably be tough to make stiff enough.
The beam on elastic footing approach will yield the same shape as combined footing (rectangular), and again probably easier to find a calculation module for.
To answer the original question:
Is it easy - Likely yes
Is it a trap - Likely maybe
I like the approach as described by @SE2607, putting in some upfront work to figure out allowable footing spans, incremental depth capacities, torque requirements, etc. This way you can check the contractors...
Similar to the grade beam ties between isolated spread foundations, you could just use a combined footing under the entire frame. Generally it will allow you to use a narrower footing than spread footings, but the length spans the whole frame. It's probably more concrete than the grade beam...
I've seen those a bunch but never knew what they were for, thanks for the insight. Are they typically fastened to each crossing CJ or just to the end walls/hip jacks?
Sometimes I see ceiling joists turned at the ends, sometimes not. Even when they are, I've never seen them "tied" to something that looks substantial enough to resist the tension. Probably the ceiling distributes this tension to perpendicular walls in combination with weak axis bending of the...
Along with JAE's concern, the existing steel column is loaded concentrically so if you end up connecting a new beam into the side you are introducing some eccentricity and moment. It may check out, but something to consider.
Through bolting with a plate on the underside of the hollowcore slab could be an alternative? Probably still want to grout some of the cells in the area, and maybe add bars if the slab needs it for flexure.
I've done a fair amount of steel moment frame design, but never considered partial fixity at the base to make them work. Are larger footings an option, such that you can satisfy the bearing pressure and keep the drift down without doing a complicated analysis with foundation springs?
Is the compression continuous across the joints at the interior column lines?
A diagram showing the chord forces would be helpful to understand how your model is behaving.
Depending on the stiffness of the "springs" at each column line you may have something that more closely resembles 3 individual trusses without much axial load going through the column joints at the chords.
If you have vertical frames at the 2 end column lines only than I would expect needing...
I think welding or drilling for bolts (or a combination of the 2 is all fine). I would definitely put some stiffeners in the column where the flange plates intersect.
If the loads are all acting concurrently (which it seems like they will be) then the 2 side walls should consider all the loading simultaneously.
You should check out PCA rectangular concrete tank tables to get a better estimation of the stresses that will occur in the new concrete walls.
See below for number 2. I know this is specifically for more than 4ft of retained soil, but still unclear as to what exactly qualifies as lateral support for the base of these CMU walls. Sliding friction and passive pressure on a footing provide resistance, but is that the intent of this part...
