Billboard sign deflection consideration

[AL89]

I am design a 70' high billboard sign, and I am wondering if anyone knows what the deflection limit at tip of the pole.

Thanks.

 

[MotorCity]

I am not aware of any deflection requirements for a billboard, but here are my thoughts. If it does deflect, it probably won't be noticeable to the passerby at that height. As long as the deflection does not contribute to significant P-delta affects, the deflection should not matter. I would expect the various strength limit states to control (flexure, shear, etc).

 

[JAE]

I think fatigue is more of an issue than deflection.

https://www.depts.ttu.edu/techmrtweb/reports/complete_reports/0-4586-4_final.pdf

http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_469-a.pdf

http://epublications.marquette.edu/cgi/viewcontent.cgi?article=1013&context=transportation_widot

https://www.fhwa.dot.gov/bridge/signinspection.pdf

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[NorthCivil]

If there is no code to guide you, I would size it based on stress and then just make a reasonable judgement call on deflection. maybe 6" is ok?

 

[JStephen]

I would think vibration might be a bigger consideration than just static deflection (and assume that's the fatigue item mentioned above)- who's reading a billboard in a hurricane, anyway?

 

[dik]

I'd be more concerned about dynamics and fatigue.

Dik

 

[thaidavid40]

Treat it like a high-level luminaire, and use AASHTO code limits to design it.
Dave

Thaidavid

 

[oldrunner]

I agree with Thaidavid40. Start with Section 2 of the AASHTO Standard Specs for Structural Supports for Highway Signs, Luminaires and Traffic Signals. Pay attention to the new fatigue section - depending upon what your columns are. Read Section 10.4.2.1.