Metal staircase attachment - no beam 3

[mechemi]

First, I'm a mechanical engineering student, so I'm not familiar with the US building codes pertaining to this issue. This is also not coursework, but curiosity.

I have encountered a staircase in an industrial setting that is anchored at one end to diamondplate only. One side of the staircase end rests directly on diamondplate (is welded), several inches from the nearest beam connection. The other side of the same staircase end rests on air, next to diamondplate, with a 3" weld between them that would be subjected to shearing through the weld thickness. There are flanges on the diamondplate but no beam supporting it at the staircase.

My gut feeling is that a metal staircase should be connected beam-to-beam at both ends, and that diamondplate should not be used as a primary structural support. However, I don't know where to look to verify this. I found guidelines on the construction of the actual staircase but not regulations on how it would be attached.

Can someone direct me to the appropriate resource, or give me some guidance backed by more experience than I have?

 

[mechemi]

Connection detail, to settle the questions about thickness and the stringer connection to toe plate.

 

[Ron]

That solves the toe plate issue! Obviously not welded.
The weld that's there is poorly profiled and not of good quality. In addition, it should have been cleaned and protected against corrosion.

Those stringers were shop fabricated. The landing looks like it was probably hatcheted and pieced together in the field.

Hopefully the structural engineer who looks at this will require it, but any repair welding should be done by a welder who is certified for structural welding and in the position for which the welding occurs. As an example, the photo shows an overhead fillet weld. This is a difficult position and the welder should show evidence of capability in this position.

 

[msquared48]

Pathetic.

Mike McCann, PE, SE (WA)

 

[dvd]

It looks like the whole arrangement is designed for washdown in the food industry, so that there are no pockets to trap anything, thus the deckplate elevated above support tubes, closed section stair risers, scallop holes at edges of stair treads, etc.

How many stair treads are on the stairway leading up from the platform?

Make sure you have permission to post photos like these, your boss/client may not appreciate it.

 

[mechemi]

I'm not sure, somewhere on the order of 8-12 treads.

I'm pulling the pictures down since i have the answer I needed - that it is worthy of bringing to the attention of a dedicated structural engineer, and that's what will be done.

Thank you all.

 

[mtu1972]

Mechemi - you should be commended for noticing this and bringing it forward. Us structurals are used to looking up to see how a building is framed (when visible) or things like these stairs, pedestrian bridges, etc. My wife will constantly remind me to watch where I am going rather than being focused on what is above us. I hope this situation gets resolved.

gjc

 

[Bagman2524]

Diamond tread plate with edges bent is quite a bit stronger than you would think. We design them using the cold formed design method described in We-Wen Yu's "Cold Formed Steel Design". An equivalent section is calculated and it's properties used to check the design. The connection details for your case don't sound like they're good though.

Faith is taking the first step even when you can't see the whole staircase. -MLK

 

[mechemi]

Thanks for all of the help. I have an appointment with a structural engineer who will analyze and detail a correction.

I will also direct his attention to another staircase I've become aware of, which has full thickness rust penetration on at least 2 surfaces of a box beam. I had no luck finding regulations on that either.

 

[TLHS]

Yeah, you're rarely going to find a situation where a standard will tell you how to simply evaluate a structure. For instance, rust is sometimes just a matter of clearing off the rusted material and calling it a day if it's not in a critical area. In some other location it might collapse a building.

With the exception of residential wood framing, structural codes and regulations tend not to be all that perscriptive about specific situations like that. They tend to require certain levels of safety and performance and give requirements on ways that you prove some of those things (i.e. how to calculate member capacities).

In straightforward plumbing and electrical for buildings you'll have a lot of details in the code that tell you exactly how you have to do specific things. Structurally, you can see the same basic thing done dozens of different ways in similar straightforward buildings, because it's at the discretion of the designer, how the load travels and where things are. Note: That's not to say that when you get to electrical and plumbing in more complicated scenarios they don't involve just as much engineering and expertise. They're just prescriptive over a much larger range than structural codes at the low end of building construction. That means you're much more likely to find a clause that tells you exactly how something must be implemented or maintained, while you're unlikely to find that in a general code for structures other than wood framed residential.