Commercial deck live load reduction

[Jmeng1026]

I am designing a deck for a restaurant and the code requires a 100 psf live load. The deck will be 12" above grade. Can I reduce the live load based on 1607.11.1 Basic Uniform Live Load Reduction in the ibc and use the reduced load to design the floor joists and support beams?

The deck is 24'x50' If I can reduce the live load would the At value be 24'x50'= 1,200 sf and the KLL = 2?

 

[jayrod12]

I'm not wholly familiar with the American codes, however north of the border where I am, you can design individual members for reduced live load based on their tributary area.

So in your instance, if you only had 2 floor beams, you could determine the reduction factor based on 600 square feet. However for a live load of 100 psf, and an area of only 600 square feet, there would be no reduction allowed as the minimum threshold is 850 square feet and even then the reduction is minor. It's much more beneficial when applied to columns and foundations.

 

[straub46]

Make sure you're even allowed to use live load reduction. Dining has footnote "m" after the 100 psf, which says you can only reduce if you meet the exceptions, and from your description it doesn't seem like you do. This might differ depending on which version of IBC you're using, since you didn't specify.

You need to use the tributary area of the supporting members like jayrod said, not the entire area of the deck.



Go Bucks!

 

[dik]

If your in Canada, the NBCC has a fairly good description of live load reduction in the commentaries.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[kipfoot]

like straub46, this would be my take:

 

[phamENG]

I agree with kipfoot and straub46 - this would essentially be an assembly area. Furniture + customers + wait staff stomping around and singing happy birthday (someday, I hope) makes the 100psf plausible.

 

[JoshPlumSE]

It all depends on whether you determine it to be an area of public assembly or merely a deck / balcony. That's a matter of engineering judgment. But, the fact that it's only 12" above grade makes me MUCH more comfortable with the idea of calling it a deck and allowing it to be reducible. Maybe not if it were a school or hospital. But, for a regular old restaurant.... I'd personally call it reducible.

Just remember that the KLL is multiplied by the tributary area, not the total area.

 

[XR250]

With the price of lumber these days, it would probably be cheaper to do a slab and then no worries on the live load