When do you use 1 in 10 year return period for wind?

[EngDM]

Can you design walls for residential applications to the 1 in 10 year return period, and then for strength use 1 in 50 years? I can't find in the NBCC 2015 or 2020 an actual application of the 1 in 10 return period. Anyone ran into this before? We are seeing some engineers get 2x6 walls to work for much taller walls than what we are used to, even designing to L/180 as per O86.

 

[jayrod12]

Personally I only use the 1 in 10 for extremely temporary structures.

 

[TLHS]

The 1 in 10 year wind stuff in the NBCC is pretty close to depreciated. The Farm Code still used it, but they've added a bunch of stuff to the NBCC this round that makes that code even more obsolete.

There's likely some stuff hiding in component standards for things like windows and doors that I don't know about, and there may be some legacy stuff in part 9 or the wood codes. For the most part, servicability checks should use the normal 1 in 50 but with the serviceability importance factor applied.

 

[canwesteng]

Nothing codified for how to use the 1 in 10 wind. I've only seen it done for temporary structures.

 

[kipfoot]

There was verbiage on this in ASCE7-10 appendix C. Explicit explanation is removed in later editions.

Also, IRC table 1604.3 note f:

f. The wind load shall be permitted to be taken as 0.42 times the "component and cladding" loads or directly calculated using the 10-year mean return interval wind speed for the purpose of determining deflection limits in table 1604.3..."

 

[TheDW]

IBC table 1604.3 (deflection limits table) note f. - the 0.42 factor

The 0.42 factor is (basically) the 10 year return period.

It is a 0.7 factor to convert 50 year to 10 year (I think this was last mentioned in ASCE 7-05)...combined with the 0.6 ASD factor to convert 700 year to 50 year. 0.6*0.7=.42

 

[TLHS]

FYI, this might be helpful for sanity checking tall walls.

https://phoenixbuilding.ca/wp-content/uploads/2020/06/Tall-Wall-Design-Guide-CWC.pdf

edit: that's actually a really useful document

 

[Brad805]

Interesting discussion. Years ago the code did have some clauses that used the q10, but that changed around 2006 or sometime.