Stringer Attachment to Wall

[McMichael05]

So as seen in the picture below, i have a stringer that was supposed to be connected to the wall using the 6 bolts in the bent plate (1A1) but the wrong bolts were installed that needed a spacing of 20"+ which obviously is not there. I cant get any values for the bolts that were used as the manufacturer doesnt provide any reduction factors. Anyway, the proposed solution was to add the 4x4 angle with bolts spaced at 12" oc. The issue i see from this is that the first bolt will experience a vast majority of the load due to the flight header connecting close by and just how the stair load is distributed. The worse case load is around 17k ASD which 1 bolt in grout filled CMU cannot take. Is there any way to prove that the bolts will act together and share the load?
[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1628091831/tips/Stair_Connection_c15tcc.pdf[/url]

 

[dik]

I don't understand the question, but the connections shown on the drawing appear to be pretty 'massive'.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[phamENG]

What bolts were installed in 1A1? Size, manufacturer, embedment, etc.

 

[McMichael05]

@dik, I am ignoring the (1A1) connection because i cant get the allowable load. So my client added in the L4x4's with the Titen HD's @ 12" oc to take the load. Basically im wondering if i can distribute some of the load that the 1st bolt (closest to (1A1)) is seeing to the rest of the bolts in the L4x4.

@phamENG, The bolts installed were 3/4" dia. Simpson Wedge All Anchors. Embedment is 3.5" min i think. Again they used a completely different bolt then i spec'd so im not sure exactly.

 

[phamENG]

The short answer is no, you can't distribute it like that. You could do an elastic distribution that would give you positive reactions in some of the bolts and negative in the others, offset or increased by the dead load of platform. So that first bolt, if you ignore the 1A1 connection, would have quite a bit of the load on it and you'd be looking at a zipper.

I don't think it makes sense to ignore 1A1 completely, though. I would check it using reductions for edge distance and see where it comes out. Then look up similar products that have tested spacing and check what their equivalent product would do. If you're close, then you can be reasonably confident since wedge/expansion anchors are more or less standardized - the technology doesn't vary significantly from one to another. Granted, you're taking responsibility for the behavior of a proprietary part that hasn't been tested, and there are certainly pitfalls to that. But I've seen lots of stair landings attached using the angles with no problems. Have any of them seen a mass building evacuation mixed with severe panic? No. So take that with whatever size salt portion you feel appropriate.