Transmission Pole Foundations

[OSUCivlEng]

I am a structural engineer that is getting into transmission line design. I'm working with a couple of experienced designers who have been doing this for 20 years. When it comes to the design of a concrete foundations, what code covers this? Are there sections in the NESC about it? I haven't really got into it yet and was curious.

 

[MikeDB]

The NESC covers some of the loading requirements, but does not address concrete design or the geotechnical design of the foundation. ACI 318 is normally used for the concrete design. There are several references for the design of the foundation, but no code.

 

[transmissiontowers]

I am a structural guy and proudly display my mistakes above ground and don't bury them like the geotechnical guys do.

If you use PLS-CADD like about 90% of the people that do line design, there is a Caisson program that is included in the package. The Geotech guy sits in the next cube over and I think he uses an EPRI sponsored program called FAD or MFAD and I hear the name L-Pile thrown around. We used to use a program called Beamcol in the old days to design drilled piers.

My take on it is you need good soil data no matter what program you use.

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I have been called "A storehouse of worthless information" many times.

 

[OSUCivlEng]

The structural design (i.e. designing the reinforcing) will be fairly straight forward. We have purchased L-Pile to do the geotechnical analysis for the drilled shafts. It looks like traditionally ASD has been used, but now LRFD is becoming more popular. Since there aren't any codes governing the design of the foundations for these structures, what is a good reference to refer to as a design aid?

 

[OSUCivlEng]

It looks like IEEE 691 might be a good book to buy.

 

[transmissiontowers]

ASCE 10 covers towers and has a few sections for connections to foundations, but does not cover foundation design. ASCE 48 covers transmission poles and has some anchor bolt design sections, IIRC. The relatively new ASCE 113 covers substation structure design and at one point we considered having a section for foundation design, but there were too many arguments among the committee on what to present.

I am no foundation person, but I would treat the drilled piers as a beam column and look into ACI 318 to design the reinforcing. You might also look at EPRI and see what reference material is available. They have a MFAD program available to EPRI members for single pole foundations and an HFAD program for H-Frame structures.

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I have been called "A storehouse of worthless information" many times.