Guard deflection

[bill1952]

Is there a maximum deflection allowed for a guard in IRC? I searched but came up with nothing. I did learn OSHA allows 3" of deflection, allowing the top of a guardrail normally at 42" to deflect to 39". (Wow) Has anyone here measured guard rail deflection, perhaps to see if under the 200 pound load it's below 36" aff?

Same apply to infill under top of a guard? Any limit to how far the 50 pounds on 1 SF can deflect the infill?

 

[Yankee Chronicler]

The code establishes loads that guards and handrails must be able to sustain, but I don't believe the code establishes any limitations on deflection.

Unless there's something in ASCE 7.

 

[steveray]

I'd say L/240 in the IRC, but what do I know....

 

[TheCommish]

Is a railing a structural member?

 

[danSAA]

From Julius Blum railing catalog engineering section:

There are few, if any, regulations or code requirements limiting
deflection in a railing but ASTM has put forth the following
criteria regarding Maximum Allowable Deflection (∆max) in their
specification E985.
For horizontal load at midspan:
∆max = h⁄24 + L⁄96
For horizontal load at top of post:
∆max = h⁄12
For vertical load at midspan:
∆max = L⁄96
In many instances, the anchorage of the railing to the floor,
tread or fascia is subject to a degree of rotation which will add
an indeterminate amount to the deflection on the post and rail.
Anchorage and supporting structure must be as secure and rigid
as possible

 

[Yankee Chronicler]

I'd say L/240 in the IRC, but what do I know....

View attachment 15827

The immediate question then becomes, is a guard or a handrail a "structural member"?

From Julius Blum railing catalog engineering section:

ASTM E985 is not a referenced standard in the 2021 IBC. Therefore, it cannot be used by a code official to limit defection in a guard or a handrail. It is, however, useful as guidance for designers.

 

[steveray]

Is a railing a structural member?

It has a loading requirement to meet so yes...Not bearing, but structural...

 

[bill1952]

I'd say L/240 in the IRC, but what do I know....

View attachment 15827

I think changed in last edition because in 2024 the highlighted line reads "All structural members excluding guards and handrails".

I kind of feel that was always the intent.

Settled in any case.

(I am worried about these being structural members and requiring a fire resistance rating. I guess this gets us back to intumescent coatings.)

 

[tbz]

Deflection is part of the testing standard in ASTM e985-xx and ICC-ES AC-273 and off the top of my head, I can't remember the composite ASTM number.

Last cycle, 2024 model publication as Bill noted, there were 2 proposals for guard deflection brought up before the committee and then the membership vote.

The first one proposed a criteria based on the testing standards that are done by mass-produced manufactures. the second was a proposal to remove it all together.

The committee voted to remove it all together from the IRC, vs adding in a specific criteria. That is what is in the model 2024 IRC

Just this past April/May at the CAH1 hearings in Orlando, I believe the folks from Washington State submitted a proposal to reverse what was done last cycle.

The committee voted it down, I believe based on previous action in the 2024 cycle.

I am pretty sure they will bring it to Cleveland this fall for the CAH2... Stay tuned.

 

[bill1952]

So, the exception from deflection for guards and handrails in the chart was added, but a test standard was kept out so far?

Is this something manufacturers want but homebuilders don't?

 

[Paul Sweet]

For all practical purposes a handrail will probably exceed the allowable bending moment before the deflection gets excessive.

 

[steveray]

For all practical purposes a handrail will probably exceed the allowable bending moment before the deflection gets excessive.

Not if you fasten it 12' OC...

 

[tbz]

So, the exception from deflection for guards and handrails in the chart was added, but a test standard was kept out so far?

Is this something manufacturers want but homebuilders don't?

Yes & No,

The exception was added because everyone who counted, those that can vote, agreed that what was there for a catch all was not intended for guards and handrails. Manufactures and homebuilders don't get the final vote, that's on the government members...

As to test standards they are not used in that manner.

The code stipulates that guards and handrails are required to meet a design load, as thus if the math does not allow an engineer's calc's to meet the text.

The next option is to prove that the calculations are just overly tilted.

An example of this are many Aluminum guards and composite guards.

Most of these manufactures prove their products comply with physical testing.

 

[tbz]

The immediate question then becomes, is a guard or a handrail a "structural member"?



ASTM E985 is not a referenced standard in the 2021 IBC. Therefore, it cannot be used by a code official to limit defection in a guard or a handrail. It is, however, useful as guidance for designers.

Y.C.

E985-xx is referenced through other referenced standards that are in the code.

So here is the question, if the code references a standard, but not another standard, that the referenced standard requires to complete its task , does the non-directly referenced standard then eliminate the referenced standard from use.

 

[Yankee Chronicler]

Most of these manufactures prove their products comply with physical testing.

Heh, heh -

At my former position, we did our own physical testing. The full-time ABO was a large individual. The boss would just send him out and tell him to lean on the guards and handrails. He called it the Bubba Test.