Tower with non pivoting vee

[rubenpezu]

Dear all,

I am modeling a TOWER, but I can't find the way to model correctly the tower.

As you can see in the attached file there are two kind of towers, one model is with the insulators of left side. This tower is done, I have modeled with a 2-part insulator. I think was right because now we are in next phase. At this moment I have to calculate the tower with the insulators of the right side.

I tried to model with two part insulators the horizontal insulators (compression) and cable (Geometry/cables) for inclined insulator (tension) but I can't connect them. If I model all insulator with cables I think will not be right because for horizontal insulators (compression) cables don't support compression efforts.

I thought model the insulators as angles but I have no idea how simulates insulators properties with angles. I have check the previous tower (configuration of left side) with angles and the results are quite different from model with 2-part insulator.

I hope you could help me. Now I am completely lost.

 

[transmissiontowers]

If it were me, I would model the right side insulators as truss elements with the appropriate area and Young's Modulus. I would put a joint where the 2 horizontal insulators meet at the yoke plate and connect 2 truss elements with a compression allowable from the insulator maker. The tension strap can be a T-Only truss element with the correct area and tension allowable supplied by the insulator maker. To attach the conductors at the point where all 2 insulators meet, you could use a clamp or if you want to let the wires swing a little, use a very short suspension insulator that is the length of the clevis attached to the yoke plate. Both wires will attach at the one extra joint.

The other possibility is to make the 2 horizontal insulators into just a braced post like on the left side of the tower in your picture. On the right side you will need a dummy beam element like the real one on the left side.

It depends on what you are trying to find out. The members in the tower will see the same loads with either solution. If you want to know if the insulators are overloaded, the extra joint for the right side and 3 truss elements will tell you if the insulators are overloaded, especially if you get any unbalanced longitudinal wire loads.

The left side is a straight forward braced post setup with no extra joints required.

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

 

[rubenpezu]

Dear Transmissiontowers,

Thank you for your reply. I am agree with you and I have modeled the tower with truss elements and using the Geometry-member-Capacities and Overrides. In this table I try tu assimilate the properties of the horizontal angles to insulator compression capacity. What I didn't do was change Young's Modulus. Should I use Young's Modulus of insulators?

In other way, I have a doubt with other tower. It is an old tower that I have to model to calculate according our new standard. And my client said to me that the configuration of angles in red are hyperestatic and PLS-TOWER is not good to analyze the hyperestaticity and the configuration of angles in green are isostatic. Why angles in red are hyperestatyc? It is not clear for me. Could you help me?

Thanks.

 

[transmissiontowers]

First, the original question. The "E" of the insulators will only affect the displacement of the wire and should not matter much, but you can enter a new "Steel Material" property with the "E" of the insulators in the XXX.SMP table. For analyzing the tower the "E" is not too important. You are just getting the wire loads into the steel tower with these "dummy insulators".

The new problem:
You have almost stumped this storehouse of worthless information. I had to look up the two terms because in 40 years I have never run across them. The hyperstatic members are what we usually call redundant members because in an old method of joints you can ignore them (if you are old enough to remember a graphical analysis of truss structures from an era before computers and calculators). The isostatic members are what I usually call lacing members and carry the shear load from leg to leg. If you look at the green members below the bottom arm, the shear load in the tower is carried by truss action down the green members and the red members are intermediate bracing for the legs. The problem is that the joints at the bottom arm will move horizontally about the same as the joints at the end of the green members and the translation of the system will induce loads into the red members which also go from leg to leg.

In a modern FEA non-linear analysis program like PLS-TOWER, the inclusion of those red redundant members is important because they will carry load and the program will tell you how much. I have to disagree with your client that PLS-TOWER will not analyze this tower correctly. I would add the red members in the model but I would not put in the joints where they intersect with each other or the green members. The tough part will be to determine the bracing factors for the out of plane buckling.

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

 

[rubenpezu]

I will make a simulation as you said for the original question.

For new problem:

I have studied in the university graphical analysis very simple, but not so much, and I have never used out of the university. I am 29 years. I would have like calculate a tower as old times but I have never had the opportunity.

I have model all angles (red and green) as truss elements and crossing diagonals, and all are continuos. In general data I activate crossing diagonals and in RLout I have put "1". Why you call red angles redundant members? I should have to model as redudant members? I thougt that red angles have to be modeled as green angles. Am I wrong?

Thank you very much for your help.

 

[transmissiontowers]

So you are 29 years old or you have been modeling towers for 29 years?

The red members are kind of like redundants in that they could be left off the model and the leg bracing could be adjusted to account for their support, but since they will carry a calculated load, you are correct in putting them in your model with the green members and making them crossing diagonals.

The short members that brace the leg and lacing members in the bottom tower panel are true redundants and can be left out.

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

 

[rubenpezu]

Dear transmissiontowers,

Thank you for your reply. I am 29 years old.

 

[transmissiontowers]

I'm double that 29 plus a few years. Been working for the same company for over 40 years.

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

 

[rubenpezu]

Congratulations,

In actual situation I think will be very difficult work so many years for the same company. At this moment I have only 5 years of experience.

 

[transmissiontowers]

I think it is getting rare that Engineers stay at one place for as many years as I have. You certainly can jump around and get much better salary increases than staying at one company, at least that is my perception. At a public utility, there is not as much pressure to stay busy with projects that bring in fees like the consulting business. The public utility engineer must stay focused on the work, but when projects slow down, they can do some research or other productive things (like working on the PLS-CADD structure models).

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

 

[rubenpezu]

I now that to have a better salary you have to move to another company. This should not be because companies lost a person that have formed and probably a competitor company have a new good worker.

I would like to use PLS-CADD and learn but working in private company I don't have time to do any research. I was last year in Powerlinne office in the PLS-CADD training but I never had the opporutnity to use.