ASCE7-05 Live Load Reduction with Load Combos 1

[cap4000]

I have a 4 story condo with an open parking level below. The steel girders will support 3 floors and a roof with load bearing walls. The question I have is when I calculate the live load reduction per 4.8.1 do I then further reduce it by 0.75 in the Load Combo per 2.4.1(4). It seems to be a hugh difference in the total weight on the girders with a summed tributary area of 1,200 square feet for the 3 floors. Any tips will be greatly appreciated.

 

[haynewp]

I would say yes because the reduction based on tributary area is different from the reduction you are taking based on the probability of certain loads acting simultaneously in the load combinations. Make sure to check the combination including 1.0 Dead + 1.0 Floor Live {Combo 2.4.1(2)} for the girders also.