Guard Rails Deflection Limit 4

[Ramezsayed EIT]

Hey all

I am designing a Guard rail in Tampa, Florida and I did a lot of research to figure out the Deflection limitations but couldn't find actual solid resource.

can you please provide me the resource for the deflection limitation when I apply 50 PLF or 200 Lbs on the top rail or vertical post.

 

[STrctPono]

Maybe someone will correct me if I am wrong but I was never aware that there was a deflection limitation? If so, I don't really understand why? This is more of a serviceability concern which I wouldn't think would apply to railings. I always assumed the lateral concentrated load was from someone falling into the railing, cart hitting it, etc. In those cases, who cares about deflection so long as it maintains strength.

 

[IRstuff]

Too much deflection could possibly induce untoward actions on the part of the person falling; if the railing, say, deflected a foot, that might cause the person to try and do something that might cause them additional, or unexpected, harm, as opposed to a railing that only deflected, say, half an inch.

It seems like an interesting question, since the larger the deflection, the less the force of impact, i.e., an infinitely stiff railing would impact the maximum impact force for any given scenario.

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[r13]

Aerodynamics in play

No, no limit, as long as strength is adequate, and spacing within code specified maximum.

 

[dold]

I got the impression that the 200lb load was not only for someone falling/leaning/whatever, but also to account for emergency personnel using it as an anchor or hoisting stuff too.

 

[bridgebuster]

Download the Julius Blum catalog, they offer guidance based on ASTM E985.

Link

 

[Bagman2524]

There is no limit on deflection of guard posts that I know of. Attached is the best resource I've found on the subject.

All I know is P/A and Mc/I

 

[JLNJ]

I believe there is an OSHA limit for the deflection of a cable used as a guard during construction.

If I recall correctly it is pretty generous. I definitely would not exceed it for a fixed guardrail.

 

[r13]

JLNJ,

It is the permissible sagging of safety lines in fall prevention/arrest calculation.

 

[Ron]

No deflection limit. When we test them, we look at deflection recovery, not total deflection. They should recover almost completely.

 

[Agent666]

In this part of the world we have a codified limit of h/60 + L/240, where h is the height, and L is the spacing between posts. This is tied to certain load cases and loading scenarios that are probably different to those considered elsewhere in the world. Refer to this design guidance for further information

Link

Generally though this requirement results in quite large limits, which when considering serviceability do actually seem quite alarming to users if you lean against a handrail and it deflects 25mm or so under a relatively small load.

 

[IFRs]

1910.29 b) 4) "When the 200-pound (890-N) test load is applied in a downward direction, the top rail of the guardrail system must not deflect to a height of less than 39 inches (99 cm) above the walking-working surface."

https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.29

 

[r13]

Good reference. Seems OSHA is quite generous.

Agent666, Your link bring up nothing. I think you miss typed a zero in the first term.

 

[Agent666]

Retired13, link works fine here, no zeros in the link so have no idea what you mean?
Attached the file to this post

 

[r13]

h/600 + L/240 My mistake. Please ignore.

 

[human909]

Not to disimilar to IFRs's post. Though downwards should be considered only half the picture.... In Australia this is a quick snip of the relevant code:

(I've seen this exceeded by lack of torsional stiffness of the beam that the handrail is attached to.)

 

[r13]

Is the 100 mm deflection due to combined actions of (a) and (b)? If it is, what is the limit for the individual case - [h/60 + L/240, or 30 mm, whichever is ...] ?

 

[phamENG]

ASTM E985 is a good place to look. It's the standard test of guardrails in buildings. I can tell you that the deflection criteria for a successful test is in section 7.2, but that's only from a reference I found - I don't have a copy of the test procedure or actual acceptance criteria.

 

[Ramezsayed EIT]

So Far the limitations I found for a 42'' x 52'' Guard rail :


AS/NZS code:
Min [H/60+L/240,1.18''(30mm)]
Allowable deflection= 0.919''

ASTM E985 Section 7.2:
Min(H/24+L/96, H/12)
Allowable deflection = 2.29''

Florida Building Code:
allowable deflection of cantilever = 2xH/120 = 0.7''

ICC (AC 273) : Min(H/24+L/96, H/12)
Allowable deflection = 2.29''
similar to ASTM E985

 

[slickdeals]

Though there are no deflection requirements, you don't want it to be flimsy. It needs to be stiff enough that someone holding it or leaning on it doesn't get the shock of his life.