JohnnnyBoy
Structural
I am re-designing a Pylon sign (30' tall). I say re-designing since the structure has been installed for a while according to my client. No exact date but over 10 years. The reason I am asking is the way I would typically design them is failing the sign.
NBCC 2015 Commentary: Billboards: Fn=Cf*Cn*q*Cg*Ce*h*lw (Figure I-24)
My question is have my assumptions always been to conservative.
Cf=1.3 depending on height/width ratio
Cn= 1.0
q= Always considered 1/50 year. Can this be reduced, to me 1/50 should be used but maybe 1/10?. (Life expectancy roughly 50 years).
Cg = 2.5. I consider it the main structural member but maybe I can reduce this to 2?
Ce = I always consider open terrain for larger signs even within a city (30' tall). Do others tend to agree?
Iw = 1.0 Normal importance.
Client is removing a sign and replacing with a smaller sign thus reducing the wind load (95% of previous wind load). Why I'm hesitating is they are only reducing load and now I am leaning towards telling them the sign overall needs to be reinforced or strengthened. Just wondering how other professionals would handle a situation like this.
NBCC 2015 Commentary: Billboards: Fn=Cf*Cn*q*Cg*Ce*h*lw (Figure I-24)
My question is have my assumptions always been to conservative.
Cf=1.3 depending on height/width ratio
Cn= 1.0
q= Always considered 1/50 year. Can this be reduced, to me 1/50 should be used but maybe 1/10?. (Life expectancy roughly 50 years).
Cg = 2.5. I consider it the main structural member but maybe I can reduce this to 2?
Ce = I always consider open terrain for larger signs even within a city (30' tall). Do others tend to agree?
Iw = 1.0 Normal importance.
Client is removing a sign and replacing with a smaller sign thus reducing the wind load (95% of previous wind load). Why I'm hesitating is they are only reducing load and now I am leaning towards telling them the sign overall needs to be reinforced or strengthened. Just wondering how other professionals would handle a situation like this.