My boss says look the other way? 17

[transmissiontowers]

I am a structural engineer and have been working for over 30 years analyzing transmission towers and poles that support wire. My boss is an Electrical Engineer with a PE. His boss is a business major. The Vice President is a Mechanical Engineer.

The problem is the analysis of towers with a skewed wind angle. Due to geometry, a wind at an angle will produce maximum loads and cause leg failure. If the wind is only considered normal to the wires, the legs are OK.

Back in the old days, we did not have the software tools to consider skewed wind. With better PC's and better software, we can now analyze hundreds of wind angles and determine which wind angle will control.

My EE boss says it is a management decision of risk vs reward and it costs too much to fix the towers when adding more equipment to the tower. As a PE, I feel it is my duty to inform him that it is my opinion that the tower will fail if the wind hits the maximum design wind speed and at the most critical direction.

The NESC code we work under has some generic guidance that the wind at an oblique angle may cause higher loads. Guying the tower inline will help brace it and reduce the leg loads to acceptable levels, but it costs more and the construction folks don't like to do it and are concerned with trucks running into the guy wires.

I have been told to ignore the oblique wind direction and allow the extra equipment to be installed on the towers. I have a few options:
1) State my concerns to the manager and let him decide
2) Run the oblique wind cases and note the failures, then run the normal wind case and note the loads and write a note in the file that the tower will fail in the right conditions.
3) Prepare a letter and have it signed by the EE and his boss that they are aware that the tower may fail.
4) Report my EE boss to the State Board of Registration for ethics violations.

Is it ethical for the EE to order me to look the other way?

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

 

[transmissiontowers]

Yes, when I started 15 Engineers shared 2 Friden/Singer 4 function calculators that had a 3" dia green CRT and a 4 stack RPN. It did have a square root button but did not do Sin or Cos. For Trig functions we shared a book of Smoley's tables.

http://www.oldcalculatormuseum.com/friden1162.html

One load case took hours to do using the graphical method of joints just to find the loads in the members. Allowable loads in the members was done by hand calculations. The graphical method was a 2D truss analysis and we did each face of the tower separately. After a few years we got fancy and used the program Stardyne to analyze towers, but had to calculate allowable loads with HP45 pocket calculators.

All the Utilities that I know of follow the NESC as a minimum and I believe some States require the NESC to be used by law. I've never had to go to court and I hope I never do. Lawyers being what they are and people waiting to sue big companies over anything that will make a buck may force stronger structures, but it seems like no matter how strong you make a structure, if it falls down some lawyer will try to prove that the engineer could have made it stronger.

AFA my problem, I think I'll go ahead and run the wind at oblique angles and report and document my findings and note my objections if the boss decides to neglect the oblique wind.

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

 

[jt12]

If you are legally obligated to design to the NESC, I have more of an issue with what your boss is doing than what I stated in my last post. You interpret the design code that you `must' design for oblique angles, and he is telling you to neglect your code interpretation. I think the path you are going down at the end of the last post is the correct one, and see where it goes from there. Make sure your boss is aware of all the risk he is potentially taking on, and that if he is going to take that risk he is going against the structural department to take that risk.

If you are not legally obligated to design to the NESC, I have less of a problem with what your boss is doing, but I would still make sure your boss is aware of all the risk he is potentially taking on, and that if he is going to take that risk he is going against the structural department to take that risk.

 

[IFRs]

Modern steel is often stronger. If you are using 36ksi steel when 50ksi is what you are getting there may be some room for you to absorb the higher loads.

 

[civilperson]

The angles used in lattice towers are 36 ksi yield.

 

[dik]

Is there much of a cost in specifying them as Grade 50? Our standard grade of steel here is 350MPa or Grade 50.

Dik

 

[JStephen]

Where the strength is governed by buckling of one kind or another, is there really much increase in design strength for 36ksi or 50ksi?

 

[transmissiontowers]

The steel yield does not matter for the compression capacity when the L/r is above Cc. It does matter a little for small L/r values but it is not very practical to change out a leg member on an existing tower.

50 ksi is generally used for the leg members anyway and 36 ksi is used for the lacing and redundants.

The statement in NESC Rule 252D that the oblique angle may cause more stress is in a Note and as such does not carry the mandatory strength of the Code and is only a suggestion according to most interpretations of the Code.

It is my interpretation that I should consider the most severe wind direction and it is his interpretation that we did not do this in the past and should not do it now.

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

 

[mrMikee]

I design elevated bins containing cement, sand and gravel, typically being four column structures. While the code provisions for quartering winds and orthogonal seismic have become more specific in the last decade or so, I think the codes have said to design wind (and seismic) for "horizontal loads from any direction" for a long time, at least from what I could find in the UBC published in the 70s.

Even though transmission towers and I design different products to different design criteria, I think you have to be aware of the physics of what's going on, and what the worst case loading would be.

Regards,
-Mike

 

[dik]

JStephen... once the slenderness is within the Euler range... fy matters nothing, only E... It is unlikely that all members are in that range, and it may be possible to economically add some local bracing to strengthen these members...

Dik

 

[Ashereng]

Like anything else in life, what you say may be heard by others. A forum such as this is open to the public. Anyone can come here and take what you say, and use it for their own purpose.

When you signed on to a project, or your employment contract, or similar situations, one of the things typically required of you is to keep certain things confidential. That also extends to engineering forums, where you ask for other's opinuions. You need to use your own professional judgement to determine how much information to give (to get a useful answer) versus confidentiality.

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

 

[btrueblood]

"I took btrueblood's comment as a joke due to his frustration and my response was in a joking manner. Life is too short to be serious all the time."

Thanks, transmission. That is what I intended. I like journalists less than I like lawyers (though, I do like the idea of stirring up a hornet's nest here at home, and then standing back to watch and laugh; how to keep it from backfiring onto some poor schlepper like you or me is the rub). Thus, the follow-up comment about cost of hiring a PR firm, was intended to also be tongue-in-cheek, but pointing out the "hidden costs of failure" that the MBA types like to gloss over during design reviews. My frustration was not over spending 8 days w/o power (I live in an area that experiences at least one 1-2 day outage per year, on average, and so like any good engineer have my own generator), but more with your descriptions of the people who you have to "sell" your design experience and knowledge to.

Good luck with your efforts, but I agree with some of the other posts here, and would advise you to keep your own copies in a safe place somewhere, just in case the finger-pointing starts.

 

[transmissiontowers]

I figured you were joking around and was joking back at you. I am in the process of writing a paper to document my concerns and reasoning to give to management so they have the facts and will be able to make a decision.

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

 

[transmissiontowers]

Very good news. My Boss has decided not to over rule my decision to run the analysis the way I want. I just have to write up a paper stating my reasons for using the oblique wind.

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

 

[mrMikee]

transmissiontowers,

For me it's always nice to hear the conclusion to these threads in particular when there is a good ending to the story.

Thanks,
-Mike

 

[dik]

good resolution... Dik