live load reduction

[delagina]

What I meant is hypothetically if I have 10 floors. On global design I use 100 psf on all 10 floors which
I find excessive as there cant be full of live load on 10 floors at the same time.

Is there anywhere in the code that says on Global design I only need 2 floors or whatever full of
Live load at a time.

 

[a2mfk]

Not that I know of, but trib area reductions take this into account, and you get to use this for every floor on a multi-story building...

 

[msquared48]

It's not the floor, but the individual members that the reduction is applied to, from the roof to the foundation, beams, and columns. I would not apply it to walls.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[delagina]

Yes I am aware of that reduction from ibc 1607.9.1. Tnx anyway

 

[SrVaro]

Yes there are allowable reduction in live loads on multiple floor structures. But not to the extent within your example. As stated earlier, there are individual member reductions based on trib area allowed per section 4.8.1 of ASCE 7-05 (similar in IBC). The most reduction you are allowed is for columns and foundations of members supporting two or more floors. Per section 4.8.2 you are allowable a 20% reduction.

Therefore, the code is making some of the same assumptions you are that not all areas will be loaded to the max at the same time.

 

[rscassar]

I'm unsure how live load reduction is treated in IBC but the loading code which I use allows a live load reduction of up to 50% for large tributary areas with certain loading types. If the 100psf is a storage load than live load reduction would not be permitted.

I never apply live load reduction for floor design but the foundations and lower columns in a 10-story building would receive the 50% reduction. This reduction would gradually reduce (less than 50% live load reduction) for the columns on the higher levels.

There can be the design live load on the 10 floors all at the same time, it is just statisically unlikely.