Anchor Bolt Spacing 8"OC seems overkill

[Rich Zimmerman]

I'm trying to check the work of my structural engineer. He's got 5/8" anchor bolts spaced at 8"OC attaching a sill plate to the top of a basement 6" ICF wall. Joists hang off the sill plate. 1-1/8" floor sheathing attaches to the top of the sill plate with 2 rows of #8 screws 4"OC. Say's it's necessary to restrain the top edge of the wall. I've NEVER seen spacing at 8" for an anchor bolt. This structure isn't particularly unusual (other than I think it's a bit weird to hang the joists from the sill plate rather than on a ledger board.)... 8' ceiling basement. 7.5' unbalanced backfill behind the wall.

So here's the big question I don't understand. Given the spacing there are 4 #8 screws attaching the plywood to the sill plate for every 5/8" anchor bolt. If we look at the cross section of the associated fasteners, the 5/8" bolt has a shear area of 0.218in^2. The four #8 screws have a shear area of 0.039in^2 COMBINED. And that assumes the screws shear before they pullout. It would seem we have nearly an order of magnitude discrepancy here.

 

[oldrunner]

Back to the wall thickness: Actual concrete portion is 6". Divide by 1/2 of the thickness and bar equals about 2-11/16"(or 3")of edge distance. Is this edge distance a problem for the shear load on from the anchor ? Is there some sort of analysis for this or did the manufacturer provide some info. I'm looking at the Fox Block web site.

https://assets.foxblocks.com/web/legacy/uploads/2017/10/1.05.01-Structural-Engineering-US.pdf.

I note that the site provides guidance for the actual wall design but leaves the anchor bolt sizing and spacing to the engineer of record.

 

[XR250]

Once the structure is up I can't get a skidsteer back there anymore, and I can't just dump over the wall if the floor is up....ugh! I'm sure 20-30 yards of dirt will be easy to push uphill in wheelbarrows....

You can rent conveyors specifically for this purpose. Had a customer use it on his house.

 

[dold]

How much more can a 3/4 or 1" anchorbolt be? I spec 1" diam throughbolts all the time for wood/wood connex. Granted, these are big retail projects where that sort of stuff is chump change... Plus 1" diam is going to eat into your breakout calcs, etc. I was about to suggest more of a side-mounted ledger, but cross grain bending is a no-no. So nevermind.