Concrete base for light poles 1

[markac]

I'm looking for a simple formula to calculate the depth required for concrete light pole bases. Known information will be: the mounting height of fixtures, EPA (effective projected area of fixtures), diameter of concrete pole base (example: 24&quot, wind speed (example: 100 mph), & gust factor (30%). Any suggestions or guidance?

 

[Ron]

markac...it will vary depending on the code used. Most reference codes will allow computing wind loads based on ASCE 7. In that case, you will apply a variety of factors to achieve your final loading. There are at least 5 factors that would apply to the computation, most of which will always be the same for your application.

 

[markac]

Ron,
Most instances will be in North Carolina - the International Building Code applies. Please provide further information & thanks in advance.

 

[MikeDB]

Standard embedment for wood poles is 10% + 2 ft., so a 70 ft. pole would be embedded 9 ft. This may be too conservative for lighting standards with small wind areas, but might not be enough in a swamp. Like all "rule of thumb" guidelines, it needs to be used with judgement.

 

[dicksewerrat]

YOU MAY WANT TO RAISE YOUR WIND SPEED TO 120+. HURRICANES COME ASHORE IN NC. NOW AND THEN. CHECK THE UBC FOR BLDG WIND LOADS WHERE EVER YOU ARE PUTTING THESE

 

[RG88]

First thought is to contact the light pole manufacturer. Most manufacturers have tested this ad-naseum and provide a depth/size of footing for wind load and soil properties. In NC the NCDOT has details for light pole foundations and I believe they have a design guide for sign and light poles. I haven't done one in a while and I am relaying this from memory. Start with

http://www.ncdot.org

and then try the Structure Design Unit Page or the Soil Design Services Page.
I remember one of the other engineer's in the office having something from Cal Trans...you could try the California DOT web page, I last recall them having a lot of good information online and available for design.

As Ron said ASCE 7 for loading. You can take this loading an use it with the sign pole footing nomograph in the Civil Engineer's Handbook 4th ed. (McGraw Hill). Or try and find one of the references above. Best of luck.