Longitudinal Load Factor

[0087159]

Halu to everyone!!If I were to design a transmission structure, what are the load combination that I will use related to the Longitudinal Load for ASD and LRFD. Is there a specific load factor for each method (RSL, BPA or EPRI method)?Well, I have a limited knowledge about ASCE 74 and I havent read it in detail.

 

[Ron]

Then I would suggest that you read it....it covers your question in detail. Don't get caught up trying to mix load application methods and factors. Pick one that applies and use it for the design.

 

[Ltwine]

The owner of the line and the company you work for usually have well established procedures for this type of work. Find and follow the design guide.

 

[0087159]

Well, honestly, I live in a third world country and I find it difficult to obtain a copy of ASCE 74.I have a limited resource, in fact, our currency is equivalent to more or less 50x one U.S. dollar.

I do not work for any company engage in power distribution or transmission. I just want to extend my knowledge about transmission tower design. I read some part of ASCE 74 through some presentations in the internet but it would be better if I can read the section related to longitudinal loading and the load combination s used.

 

[transmissiontowers]

Maybe a good technical library would have a copy of the new edition that just came out. ASD for transmission towers does not make for an easy design. The NESC which prescribes what loads must be applied also specifies the overload factors to be used. The NESC and LRFD are a much better match.

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

 

[0087159]

In our country, ASD is still being used. As far as I know, our structural code for steel has not been change but we are allowed to use LRFD which is now being taught in some universities.

We dont have ice here but we have strong winds. Unless our electrical code adapted some provisions of NESC, then, maybe LRFD is better than ASD to use. We still need to do some researches to prove that LRFD is much better than ASD for transmission towers.

 

[ToadJones]

Can I ask what country you are in?
It has me interested for some reason.

 

[transmissiontowers]

I'm in Texas but you probably meant the OP.

ASCE 10-97 which is being revised now, is the bible of transmission tower design and is slanted to LRFD and usually assumes that the loads have an overload factor. The allowable member load equations for compression, tension, bearing, and bolt shear in single angle members are based on testing done before my time and I've been analyzing towers since 1973. I guess that ASCE 10 is in a way ASD since it gives allowable loads in members but we usually have low overloads on high wind cases (the NESC specifies the OLF for Ice cases and a minimum of 1.0 for hurricane wind).

Transmission towers do not house people like buildings or carry cars like bridges do, so there is no huge safety factor to protect human life. If they fall down in a hurricane, we rebuild them and re-route power another way until the circuit is restored.

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

 

[0087159]

I live somewhere in Asia. I am so much interested on how they design towers.