We always sawcut slabs-on-grade except in extremely rare cases. And in those cases, we're providing something like 0.5% Ag as the steel to mitigate the size and randomness of the cracking.
We also specify that the contractor needs to layout the sawcuts before the pours, and cut half of the bars...
Have a plan in place, even if just in your back pocket, for what you're going to do if you discover voids in the wall when you remove the insulation to do any reinforcing for the opening. I've had it on multiple instances where there are notable, unacceptable voids in ICF walls.
Vibration is going to be the largest concern for a running track. I'd do some digging into that side of things and then come back with questions. I anticipate needing likely stiffer than even what you're proposing to keep the vibration checks in place.
When I do these, I notch the column and beam to allow a bearing connection for the brace. And I also only design them for compression. When in tension I ignore the contribution.
I don't have an answer for you, but this is a super interesting question that I can 100% see coming up.
Forgive the question, I'm away from a code and you seem to have done a bit of digging already, but are the extra requirements you mention in 4.1.8.1.18 for the lower seismic loading change...
That's all well and good, but money talks and trusses are the best bang for your buck. If I tried forcing ridge beams on every client, I'd be out of designing houses where I practice.
You likely won't get someone telling you this is fine. Are you an engineer? If so, the design aspect is easy and we can certainly point you in the right direction. If not, hire an engineer.
If the beam works as simply supported, you could sever the top 1/2 of the beam at the middle support and turn it into two beams.
As far as I understand it, doesn't matter how stiff the beam versus column is, the statics is the statics and for a UDL continuous equal span beam the centre support...
I pretend the corner isn't that stiff to be completely honest. Often with scissor trusses like those shown, I frame a full height wall and the first truss doesn't start until 2 feet in from the corner. so there is already some flexibility in the wall system by the time you get to the first...
35 feet isn't that far for the roof plywood to act like a folded plate diaphragm. The detailing is a bit onerous if you truly want to get everything to calc out. But it's done fairly regularly.
Usually we get the truss supplier to design around it being pin-roller, but keep the lateral deflection to 1/2". Then just assume the walls are flexible enough to accommodate 1/4" each at the top of the wall, which is generally tolerable.
