Mono Stringer Stairs deflection issue 3

[nomi640]

Hello,
I bought modular two mono Stringer stairscase from bocani from Montreal, after installation staircase feel like suspension bridge, both stairs have side to side deflection and also jumping up and down.

48" wide thread have middle Stringer of 15" and 42" stairs consists of mono stringer of 7" span for 15 feet (9 feet ceiling height).

I will really appreciate if someone can help me to reduce the deflections.
I also attached FEA they provided for your reference, also below is video link

https://youtu.be/l9Df8ukuGik

Thanks

 

[KootK]

Frankly, I find it a bit distasteful that you're cutting and pasting this much of your conversation with your engineer into this thread. If what you want is a discussion between him and us, invite him here where he can defend himself amongst folks who can speak his language (engineering, not Quebeauois). I'm happy disprspect the work...but not the man. At least not in absentia.

 

[ldeem]

Assuming strength is ok you might find you can live with the deflection. I used to work in an office with under designed floors that bounced as you walked. It was little annoying at first but I got used to it.

 

[glass99]

Could you not angle bracket the bamboo treads to the drywall? Even just one tread near midspan would laterally stabilize the system and zero out a lot of the torsional issues. You could make some nearly invisible brackets if you are clever about the detailing.