Looking for a little help

[WickedJester]

First just want to give you all a little background about myself. I graduated with my CE degree in 2012 with a focus in environmental. Right out of school I started with a construction company and have been with them ever since. I am also in the military and an engineering assistant, so that entail filling the role as a CAD, GIS technician and as a surveyor.

At my current job I do almost no design work and would like to get my PE at some point so I have started searching for different positions.

One position I just interviewed for has me racking my brain as I feel it is something simple but would like some help figuring it out. In the interview I was asked about designing a foundation for electric distribution poles; for example soil, aggregate, and concrete based.

So I feel like I should start with refreshing my statics and then where should I go?

 

[bimr]

Electric distribution poles typically do not have a foundation. For thees poles, it would be a geotechnical issue. You might have a soil anchor.

Transmission towers do have foundations.

 

[WickedJester]

Thanks for the reply!

I understand distribution pole typically do not have foundations. A guy wire/soil anchor would be placed where applicable; some areas do call for free standing poles either due to obstructions or landowner restrictions. So I am looking at a free standing pole, where a guy wire/soil anchor is not applicable for whatever reason.

I agree, for free standing distribution poles it would be a geotechnical issue to determine if the in-place soil could support the forces applied by the pole and connected wire. So I am wondering if a geo report was done on the soil to determine what its load bearing capacity is; would it be a statics problem after that to determine forces from the wires and exterior forces (wind, rain, ice) and the forces acting on the pole embedded in either the ground, aggregate, or concrete?

 

[oldestguy]

I hate to say it, but you should have a mentor. Sure you might be able to come up with a design, but there are all those codes out there and convention for plans, etc. that you probably didn't get much coverage on in college. Not sure how you might do that, considering competition and other factors. Perhaps ask that the work be farmed out to a consultant, at least for a while. Also, you may have trouble showing that your work type is suitable for the experience needed for the PE. The first several years out of school usually are still a much learning process.

 

[SlideRuleEra]

WickedJester - The "design" of distribution pole embedment is often prescriptive. Make a visual evaluation of the soil and power line geometry, look on a chart, pick the solution that is called for.

Is the job with an electric utility or a contractor? If it is with a utility, perhaps it has career potential. If it is with a contractor, likely a job, with little future.

As bimr stated, transmission structures are another, more complex issue that do require design.

Assuming that "design work" is required for a PE is an oversimplification. Design is a straight forward way to prove that you have suitable engineering experience. There are other ways, what is important is to have valid references with appropriate credentials, and to submit a well written application to the Engineering Board. Of course each state has their own details, but look at the NCEES Model Rules (pages 8 and 9), no requirement for design work:

https://cdn.ncees.org/wp-content/uploads/2012/11/Model_Rules_2014.pdf

Unless your part-time military job as an Engineering Assistant requires an education that meets the state's requirements (doubtful) for a PE license, it is probably of no value to towards required experience. It will be of value to you, but not to the PE board.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[WickedJester]

The position I am interviewing for is an entry level civil engineering position.

I agree on both accounts; I would need a mentor starting at this new company and farming out the work initially would be the best option. I have exposure to specs and codes through both of my current occupations, but I also discussed in the interview since I have no experience in the electric distribution industry that I would need to be trained.

Yeah my current experience would not qualify me for the PE and I am trying to switch to a position that would.

 

[WickedJester]

I am interviewing with an electric utility company and believe it to have great career potential.

I'm curious if there is a method, assuming arbitrary values, that one could determine the forces acting on a distribution pole and if the soil or other material it is directly embedded into would be able to support it. Not trying to reinvent the wheel hear, just want to try and do a simplified calculation of the forces acting on a pole directly embedded in soil or possibly other material, ie aggregate or concrete.

 

[SlideRuleEra]

There are many ways, go to this page of my website and download "Pole Buildings Design" by Patterson:

http://www.slideruleera.net/miscellaneous.html

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[Lomarandil]

As I believe you noted, determining the forces acting on the pole is basically statics. There are a number of simplifications and improvements made specifically for electric distribution/transmission structures, but you'll pick those up from your mentor as you start the job.

Typical sources of load are gravity, wind, ice, and wind combined with ice (reduced values of each).

For the foundations, the vertical capacity follows basic geotechnical/foundations principles, either using a prescriptive chart (common for distribution-level poles) or the guidance of a geotech (for transmission-level or complicated situations).

The lateral capacity of a pole foundation is often simplified with a method like what SRE posted or Brom's method. I think you can find a reference to the latter in the AASHTO Luminaire guide. Complex problems may use a software solution like L-pile (with parameters provided by a geotech).

 

[boo1]

"Any utility company, whether it is investor owned, cooperative, municipal, or telecommunications, will
probably have its own way to design distribution lines. While there are differences from company to
company, the design methods will likely be similar because they have been built from the same standards.
There are two typical standards for distribution pole design – National Electrical Safety Code (NESC) and
the American National Standards Institute (ANSI O5.1). There are additional guidelines for Electric
Cooperatives imposed by the Rural Utilities Service."

RUS has documents on transmission towers attached

 

[boo1]

White paper on utility dist poles attached