Parapet acting as a guardrail

[Croceng78]

I am designing a wood stud (that supports a mezzanine floor) with a 42" tall parapet. The question I have is whether the interior lateral partition load of 5psf acts simultaneously with the guardrail load of 200# at the top of the parapet. Additionally, would the interior lateral partition load be applied to the full length of the wood stud (including the parapet)?

 

[dik]

Check the wording of the code. They are generally taken as independent.

 

[haynewp]

I am about 99% sure you won't find anything to confirm combing these loads, but loads that could happen simultaneously within the load combinations are usually expected to be additive. Most engineers (myself included) I know would design for the guardrail load and not think to add the partition 5 psf. It seems odd to add both for a 42" parapet wall, but I guess technically correct.

 

[haynewp]

I just found the below in IBC 2018, so not req'd for 42".

1607.15 Interior walls and partitions. Interior walls and
partitions that exceed 6 feet (1829 mm) in height, including
their finish materials, shall have adequate strength and stiff-ness
to resist the loads to which they are subjected but not
less than a horizontal load of 5 psf (0.240 kN/m2).

 

[RWW0002]

Based on the wording of that section it sounds like even for walls taller than 42" the 5 psf is a minimum - so non-concurrent as long as "rail" loading controls.

 

[ANE91]

I generally disagree with the other comments.

I understood from your post that the stud is continuous beyond the floor (i.e., balloon-framed). In that case, part of the stud is fulfilling the “interior partition” function, and the part of it that cantilevers up beyond the floor surface fulfills the “guardrail” function. Why wouldn’t the loads be concurrent?

Guardrail load acting opposite to the partition loading would govern. The partition load is 5psf x stud spacing, applied along the floor-to-ceiling height of the stud.

Idk that I’d call it a parapet, if it’s indoors, which mezzanine implies.

 

[haynewp]

I agree with that if it's balloon framed.

 

[RWW0002]

It appears to me the code is pretty explicit that they are non-concurrent based on the snippit above. It may however be a good idea to design for both even if not specifically required by code. Especially in the balloon-framed case mentioned above.

That being said, I think the chances of the 200# guard load (i.e. someone impacting a guardrail) actually acting concurrently with a 5 psf lateral load (that is generally taken to be a minimum load for air conditioning pressure changes, slight interior wind load or a minimum load for connections and general stability/serviceability) is very very small.

I might be more tempted to combine the 50 plf rail load with the 5 psf (thinking more along the line of a group of people leaning on a rail). This in my opinion might have a much higher chance of acting concurrently with say an air conditioner cutting on and causing a pressure difference..

 

[SE2607]

I say non-concurrent.
Just my opinion.

 

[haynewp]

That being said, I think the chances of the 200# guard load (i.e. someone impacting a guardrail) actually acting concurrently with a 5 psf lateral load (that is generally taken to be a minimum load for air conditioning pressure changes, slight interior wind load or a minimum load for connections and general stability/serviceability) is very very small.

I've never opened a door to an interior room and felt 100 pounds of resistance to me opening the door (5 psfx3'x6.67' man door). That pressure plus someone applying 200 lbs horizontally to a guardrail simultaneously would be an interesting case to see.

 

[XR250]

I always considered it being from a hurricane with the doors or windows open.
Even if it ain't I think 5 PSF is a reasonable number just to make sure stuff is reasonably constructed.

 

[RWW0002]

For what its worth.. See below from IBC commentary.

I still say letter of the code is non-concurrent. Except for special circumstances or conditions this seems reasonable. However, 5 psf should not be a killer in most cases anyway.

 

[dik]

I am about 99% sure you won't find anything to confirm combing these loads,

Any codes I've come across stipulate the loads are separate. From NBCC 20.

 

[jayrod12]

dik, I believe they're talking about those two loads specifically don't need to be acting concurrently, i.e. the 0.9 kN and the 0.7 kN/m are separate.

But I also agree with others that it doesn't need to be considered acting concurrently with the 5 PSF (0.25 kPa) interior partition load. Assuming general proportions for the studs, and if we take pattern loading for the stud design, i.e. partition load on only the projecting portion of the stud and nothing on the backspan helping, or only on the backspan but not on the projecting portion, it's likely not a significant tax on the stud design compared to just the guardrail load.