Wind : Importance Factor

[slickdeals]

Does a rooftop unit, mounted on a building with Importance Factor of 1.15, be also designed for I = 1.15 or can it be lowered to 1.0?

 

[JedClampett]

IMHO, you need the same importance factor for the rooftop equipment as the building.

 

[ron9876]

Same here.

 

[azcats]

Maybe you could get away with 1.0 if the OC III was based on occupant load and RTU is not over occupied space.

Or if the OC is based on hazardous materials and the unit's failure wouldn't be detrimental to the facility.

These are stretches though that I might use to justify something existing.

 

[Ron]

Ditto....importance factor applies to the whole design.

As an example...all school facilities in Florida must have 1.15 factor applied. I design a lot of canopies for schools...1.15 applies for those, yet they do not usually impact the main structure.

If you have an AC unit on the roof and the building stands at the design pressure but the rooftop unit flies off and goes through one of the walls because it was designed at 15% less, well.....

 

[slickdeals]

Copy that.

 

[weab]

Ditto Ron.

 

[csd72]

In my opinion,it should be designed to the same importance factor unless you can prove that its failure will not compromise the building envelope or the integrity of the building.

Very difficult to do but it may be possible where the failure criterion is more serviceability than structural failure.