Fig I-8, NBCC

[calculor1]

Quick question regarding note 2 attached to Fig I-8 (C and C loads) in the NBCC structural commentary. The note states " The abscissa area in the graph is the design tributary area within the specified zone". Does that mean the tributary area for the member under consideration or the area of the specified zone?

 

[jayrod12]

trib area of member in question.

 

[PicoStruc]

Are you sure Jayrod ?

For me it seem it really mean the area of zone E ou W !

 

[jayrod12]

That's how it's been explained to me. In all honesty though, when I design I just use 1 m^2 to determine my loads.

read it again "The abscissa area in the graph is the design tributary area within the specified zone." To me that reads you use the trib area of whatever member (stud, girt, column, etc) you are designing. The zone you are in just determines which line you pull your CpCg off of. It's their own version of LL reduction in my eyes.

 

[PicoStruc]

Jayrod, I agree with you. I read too fast, I missed the word "tributary".

I have the french version where the word "Design" is replaced by "Theorical" due to translation. If you miss the word tributary, the sentense can be intrepreted as "The theorical surface within he specified zone"

My mistake !

 

[jayrod12]

Darn frenchies! Just kidding,

 

[calculor1]

That would be my interpretation as well, however a coworker asked the NRC for an interpretation and they said it was the area of the zone and not the tributary area of the member under consideration. I also checked several older textbooks and they also use the member tributary area.

 

[bobby83]

It wouldn't make sense if it was the area of the zone. The way I see it, gust speed can be higher for a small area, thus a higher CpCg