0.7 deflection modifier on interior walls? 3

[Revv]

Hey Guys,

Does anyone know if you're allowed to take the 0.7 deflection modifier when designing interior walls? I can't seem to find a clear answer, the 5 psf is often treated as a "wind" load but not sure it actually qualifies for this factor.

Thank you!

 

[Once20036]

Not sure what code you`re looking at, but IBC `15 section 1607.14 requires 5psf load on interior partitions.
Section 1607 covers live loads. This means 1) it's not a wind load, 2) it needs to be factored by 1.6 for LRFD combinations, and 3) the wind load deflection modification factor isn't applicable (table 1604.3 footnote f).

I`ve always thought about the 5psf as being a possible mechanic overpressure or as a possible errant wind gust so I`m not a huge fan of this reading of the code, but that it how its written.

 

[phamENG]

I've taken it as a catch all for things that could apply a force to the wall - a gust of wind through a temporarily open door, pressure differential, ramming it with a bed frame or dresser while you move in. So I'm okay with the live load approach.

 

[hawkaz]

it is my understanding that this is a seismic reduction factor. It should not be applied to the 5 psf minimum lateral load.

 

[Aesur]

I agree with Once20036, the 5 psf is a live load requirement for interior partitions. Many engineers don't realize this and think it's a wind loading because it's easier to throw it into software as a wind loading typically.

I assume you are talking about the 0.7(W) in the older codes and now 0.7(0.6)(W) for ultimate C&C pressures. This is intended for C&C wind loading only to get the speeds to a 10 year MRI for deflection design. The 0.7 factor does not apply to MWFRS loading.

If you are designing per codes that have wind pressures at ultimate state you need to adjust the 5 psf if you are going to input as a wind loading, which would be 5/0.6 = 8.3 psf when input as wind loading to account for the 0.6W adjustment when checking deflection per ASD combinations. If you are inputting as intended as live loading, then the ASD factor is 1.0L for ASD combinations (often used for deflection checks).

 

[XR250]

For ASD, I have taken it if I just had to make something work. I always assumed it was from wind.