Eternal Mystery of the Universe #1 - 1-1/4" Guardrail
Eternal Mystery of the Universe #1 - 1-1/4" Guardrail
(OP)
This issue comes up all the time for me and how it came about is one of the eternal mysteries of the universe in my mind. I always tell folks they can't use 1-1/4" STD pipe guardrail because of the 200# concentrated force at 42" makes it such that it just doesn't work in bending. Then, I get the "well it's the way we've always done it". Code officials never seem to catch it, but it doesn't work unless you start to count on a FE model that spreads the load between posts, etc. And then it's still questionable at best IMO.
Then, I see arch's spec 1.50" O.D. handrail/guardrail, which of course doesn't exist in the Pipe shape realm. So I'm curious, A) how people justify using 1-1/4" (1.66 O.D.) std pipe guardrail, and B) what do you all tell clients if you're on the same side as me, that it has to be 1-1/2" STD Pipe (1.90" o.d.)
Thanks!
Then, I see arch's spec 1.50" O.D. handrail/guardrail, which of course doesn't exist in the Pipe shape realm. So I'm curious, A) how people justify using 1-1/4" (1.66 O.D.) std pipe guardrail, and B) what do you all tell clients if you're on the same side as me, that it has to be 1-1/2" STD Pipe (1.90" o.d.)
Thanks!






RE: Eternal Mystery of the Universe #1 - 1-1/4" Guardrail
After that you either need to take advantage of an allowable stress increase (IBC 1607.7.1.3) with a working stress design, or use the newer ASD method with plastic section modulus.
It's still cutting everything down to the razors edge. I'll push for 1.5" Dia. std pipe whenever I can get it. The worst is when architects absolutely require a 1.5" stair stringer, which is smaller than the handrail. The weld detail is awful.
RE: Eternal Mystery of the Universe #1 - 1-1/4" Guardrail
In my opinion, the only way to justify it is to spread the load to more than one vertical post.
DaveAtkins
RE: Eternal Mystery of the Universe #1 - 1-1/4" Guardrail
In the older OSHA specs, loads were given without any indication of acceptance criteria, "shall support XXX lbs", not "shall support xxx lbs without exceeding some arbitrary allowable stress". That is, specified loads could be interpreted as failure loads, not service loads. So if they specified "shall support 200 lbs" and your handrail supports 201 lbs, you're good.
And lastly, handrail specification indicated "or members of equivalent bending strength", so using closer post spacing allows you to use smaller rails, etc., if desired.
Anyway, it's all a mess, and you can work the numbers a lot of different ways. I'm not aware that handrail failure has been a big problem, though, rather lack of handrails or falling through handrails, etc.
RE: Eternal Mystery of the Universe #1 - 1-1/4" Guardrail
This doesn't help the designer, unless you call out a higher material grade, which will probably cost the fabricator more money in material costs. Ask for A53, you get A500 for nothing extra. Ask for A500 and there's a premium.
RE: Eternal Mystery of the Universe #1 - 1-1/4" Guardrail
RE: Eternal Mystery of the Universe #1 - 1-1/4" Guardrail
RE: Eternal Mystery of the Universe #1 - 1-1/4" Guardrail
RE: Eternal Mystery of the Universe #1 - 1-1/4" Guardrail
Back in the mid-70's on the MN Iron Range. The Pipe-Fitters would claim the handrail work because "they are pipes". We had several projects where we changed to rod handrails and flat bar posts. Because it was so different, we had testing done on both the posts, the rods, and three post assemblies to prove that they could carry the required loads.
In theory, we may have spent more on material, but the field fabrication and installation labor was supposedly cheaper.
gjc
RE: Eternal Mystery of the Universe #1 - 1-1/4" Guardrail
RE: Eternal Mystery of the Universe #1 - 1-1/4" Guardrail
RE: Eternal Mystery of the Universe #1 - 1-1/4" Guardrail
RE: Eternal Mystery of the Universe #1 - 1-1/4" Guardrail
I have also worked at a place where we did the calc's and computer analyses and determined that schedule 40 pipe did not work so we went to schedule 80 for the posts. We limited the post spacing so that the handrails could be schedule 40. Not my idea. I bet the steel fab shops loved working on those handrails, and I bet more often than not the posts were also schedule 40.
gjc
RE: Eternal Mystery of the Universe #1 - 1-1/4" Guardrail
Either OSHA or the building codes may specify a minimum size where also used as a handrail, regardless of strength.
RE: Eternal Mystery of the Universe #1 - 1-1/4" Guardrail
RE: Eternal Mystery of the Universe #1 - 1-1/4" Guardrail
RE: Eternal Mystery of the Universe #1 - 1-1/4" Guardrail
RE: Eternal Mystery of the Universe #1 - 1-1/4" Guardrail
There was a Modern Steel Construction article a few years ago that addressed this issue. If I remember right, they made an argument that music iron doesn't fall under the AISC spec. However, I still design them this way.
RE: Eternal Mystery of the Universe #1 - 1-1/4" Guardrail
RE: Eternal Mystery of the Universe #1 - 1-1/4" Guardrail
My issue is that if I don't check it and there is an issue, I'm at fault. So I figure I might as well do it. And before anyone says "if you exclude it in scope", I just say, a lawyer won't care. And I know the first question, "rail loads are in the structural chapter of the code and you say you are a structural engineer right?"
So I usually do the basics and move on and just say 1.5" std. If they use something else and don't tell me, at least I tried.
RE: Eternal Mystery of the Universe #1 - 1-1/4" Guardrail
Dave
Thaidavid
RE: Eternal Mystery of the Universe #1 - 1-1/4" Guardrail