0.6D+W Load Comb and 1.0 Factor of Safety

[pettus71]

This old thread deals with an internal discussion we are having in my office currently.

thread507-202887

In the referenced thread, WillisV states the 0.6D+W combination for overturning assumes a 10% over-estimate in the gravity load (0.9D). Does anyone have wisdom or guidance as to where this idea of an overestimate comes from? Has the wording in the newest IBC cleared this issue up?

Thanks,
Steven

 

[WillisV]

It comes from WillisV's posterior

 

[msquared48]

"Overestimate" in the sense that it may not weigh as much in actuality as the tables allow.

Mike McCann
MMC Engineering

 

[cliff234]

I think it's just to provide a bit more than a 1.5 safety factor against overturning. 1/.6 = 1.667, and to get it closer to the LRFD load combination of 0.9D + 1.6W which gives a 1.78 safety factor against overturning. (based on ASCE 7-05)

 

[pettus71]

Great. Thank you all. Glad to see you are still around WillisV; your answer in the old thread helped clarify the questions we were having.

 

[WillisV]

Glad to be of assistance - I'm happy I'm still around as well, much better than the alternative.