Column live load reduction

[wag2483]

If a 1st story column in a multi story qualifies for live load reduction, is roof live load reduction also applied or is the roof reduction treated as any regular floor? The latter is what I've noticed in examples, yet the first sentence of asce 4.7.1 states except roof uniform live loads

Also have seen discrepancy with how At is calculated for a 1st story column. Is At the total trib area of all floors above or only the 1st story area?

Thank you

 

[EngDM]

At least in the NBCC the area you take for LLRF is the total area supported by the column. It says that the area is floor or roof, or combination thereof. I'd imagine it is similar to what's done in the US.

 

[KootK]

Also have seen discrepancy with how At is calculated for a 1st story column. Is At the total trib area of all floors above or only the 1st story area?

Every square foot of supported structure that contributes reducible live load to the element being considered is fair game for reduction. The whole idea is that, the more you collect, the less likely it is statistically that what you collect will be at full intensity.

If a 1st story column in a multi story qualifies for live load reduction, is roof live load reduction also applied or is the roof reduction treated as any regular floor? The latter is what I've noticed in examples, yet the first sentence of asce 4.7.1 states except roof uniform live loads

The last time that I looked into this was years ago but my recollection of the state of the union at that time was:

1) There was a clause or note somewhere that said "only loads shown in the table below can be reduced". Since roof LL was not in the table but, rather, else where in the standard, some folks were not including roof live load in roof reduction.

2) Some ambitious folks reached out to the code writers and they confirmed that it was not their intent to exclude roof live load from live load reduction.

I've been reducing my roof live loads.