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RE: Tall light pole foundation

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Rich:

Such lights, that you just described, are called HIGH MASTS.

The Structural Design Principles are basically the same as it has to be for any other light poles.

The prime concern is the STABILITY analysis; it has to be safe against OVERTURNING and SLIDING. The depth of the foundation and the eventual proportioning of the foundation concrete sections, all depend upon this STABILITY requirement. The self-weight of poles & luminaires (lights)are not that significant and the only thing that matters are the wind forces. And, the wind forces do depend on the "design wind speed" considered and the "exposure" category for the site. 

I have designed foundation for such a HIGH MAST.  This was for a 30 m high high mast for a foot ball field having 24 nos. of luminaires; the dia of pole was 960 mm or 38-in. The design wind speed was 160 km/hr or 100 mph and the exposure category was C. The bearing capacity of soil was 150 KN/m2.

The design details finalized & built are as follows:

       - a spread footing   : 4800 x 4800 x 600 thick (mm)
       - pedestal (or neck) : 1400 x 1400 mm (2000 mm high)  
       - depth of foundation: 2500 mm from the finished grade. 

I hope this helps.

Syed Faiz Ahmad; MEngg, M.ASCE
Senior Structural Engineer
Saudi Oger Ltd
Riyadh, Saudi Arabia


-----Original Message-----
From: rlewistx(--nospam--at)juno.com [mailto:rlewistx(--nospam--at)juno.com]
Sent: Monday, December 01, 2003 8:46 PM
To: seaint(--nospam--at)seaint.org
Subject: Tall light pole foundation



I was asked to design a foundation for a tall light stand.  This is the kind found in a football or baseball stadium.  It will be 80 feet high, plus or minus, with a rectangular pattern of lights, 20 or 30.

I have designed foundation for lights in the past, but not this tall or heavy.  Are there design standards for designing the foundation and anchorage?  I have the COM624 program and the FL Dot program for drilled pier foundations.  I know my design will be site specific with local geotechnical properties used in the design, but in general, for those of you who have designed these before, how deep can I expect the foundation to be?  What size drilled pier would be appropriate?  I can see it being at least a 24" dia., perhaps 30" or 36".

I appreciate any insight others may give me regarding this.

Thanks.

Rich


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