Exterior fire escape connected to old brick wall 7

[Robbiee]

Hello all,
Did a design for an exterior fire escape to service second and third floors of a commercial/residential building. Provided one row of new columns on one side and connected to the building on the other side. The client didn't like the columns and wanted the stairs supported by the old brick wall as shown in the attached sketch. Although this can be seen a lot, I did not like it and did not feel comfortable hanging the stairs off of the old brick wall. Any comments are appreciated. Thanks

 

[hokie66]

I would not do it.

 

[jayrod12]

It's a trap!

Seriously no, not unless you could somehow connect it to the floor and roof diaphragms.

 

[bookowski]

Although they were built this way historically it definitely does not work and should not be done. A 2 wythe wall as you are showing in general does not work if you check it for gravity + out of plane wind loading. There are plenty of them out there, but I've run the numbers many times and they don't work on paper. The fire escape definitely doesn't work. You need columns. If the columns become a major issue then you can do as jayrod noted and tie the T/C couple into the diaphragms - but if you go this route you need to do some serious work inside to justify developing the force and showing that a diaphragm even exists that can transfer the force.

Don't let them convince you that because it's been done that way it works. Everything that has ever failed was done that way and worked until it failed, then it didn't work.

 

[JAE]

There's a lot of cities across the US that don't allow cantilevered fire escapes anymore.

Check out Eng-Tips Forum's Policies here:
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[Tomfh]

 

[JAE]

Where did that photo come from?


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[Tomfh]

http://en.wikipedia.org/wiki/Fire_Escape_Collapse

 

[CELinOttawa]

My God. I'd come back to simply post another "no" vote, but what a powerful photo! Certainly serves to remind us of our obligation to the public.

 

[Bagman2524]

Ditto other's sentiments. Doesn't look like a good idea

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

 

[TehMightyEngineer]

I've seen an unreinforced brick wall with a simple 12" water line supported off of brick with a very similar cantilever in an old paper mill. The wall was deflected outward at least 2 to 3 inches. We resupported the pipe with columns fearing it would blow the load bearing wall out.

I can't imagine what a 3 story fire escape would do with a few dozen people running down it away from a fire. Oh wait, I can, someone posted a picture of it.

Maine EIT, Civil/Structural.

 

[bridgebuster]

Interesting reading on the history of fire escapes

http://www.uvm.edu/histpres/HPJ/AndreThesis.pdf

NYC Building Code requirements for fire escapes. If I'm reading section (q) correctly, it prohibits cantilever brackets for new fire escapes on existing buildings.

http://www.nyc.gov/html/dob/downloads/rules/1_RCNY_15-10.pdf

 

[Ron]

Tell him you can do it by removing the existing brick wall, adding appropriate structural columns inside the wall and rebuilding the brick wall to achieve the look he wants and the structural capability that you and the public require.

That will make the exposed column approach (4 of them, not 2) all the more attractive!

 

[ornerynorsk]

. . . . unless, of course, it's some macabre prison building and the goal is to effectively dispatch those who have escaped the fire ??? Or not.

I get the willies when I think about hanging stuff off of old brick walls. Some old buildings are held together by little more than mass and gravity, the mortar has long since failed.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[kylesito]

Ron's suggestions, while intended to be sarcastic, actually leads to a solution that might work. What if you built columns inside the building but projected outriggers through the wall to support the fire escape?

I doubt it's aesthetics your owner is concerned with...probably feels it is cheaper. But if he is only interested in aesthetics, some variation of this might be OK.


PE, SE
Eastern United States

"If a builder builds a house for someone, and does not construct it properly, and the house which he built falls in and kills its owner, then that builder shall be put to death!"
~Code of Hammurabi

 

[stookeyfpe]

For new construction the IBC prohibits the installation of fire escapes except in cases where the location of the building in relation to the lot line prohibit the use of exterior stairs. See Section 3406.

 

[dcarr82775]

You could run vertical strongbacks continuous between floors. The strongbacks would be tied into the floor framing to resolve the eccentricity, and thru-bolts in the brick to take the vertical component of load. The stairs/platforms would be hung off the strongbacks. Similar to Ron's thought, only you don't remove/replace the brick.

Ugly and probably too expensive, but no columns.

 

[Robbiee]

Thanks all for the comments. This was few months ago and the only alternative option I proposed was exactly what bookowski said. I did not hear back from them and they have not built it yet. The reason for posting this was a phone call I received from another person asked me if I can design a fire escapes for another building. I asked him: are OK with adding new columns? he said no, We want to use brackets supported off of the brick wall. I told him: I can't do that. It appears we are all on the same page on this one.