Angles welded in TOWER
Angles welded in TOWER
(OP)
Hi,
I´m new in the forum. I am new working with software TOWER of powerline. I have to design a small tower, the complete head is welded. I have seen that in the examples of TOWER, in the library of tower, there are a kind of angles SAW (single angle welded) but all of them are really big. Are there any table with dimension of this size? I'm from Spain and here we don't use inches, and I want to finde the dimensional characteristics of this angles to configure the angles we use.
Thank you very much.
I´m new in the forum. I am new working with software TOWER of powerline. I have to design a small tower, the complete head is welded. I have seen that in the examples of TOWER, in the library of tower, there are a kind of angles SAW (single angle welded) but all of them are really big. Are there any table with dimension of this size? I'm from Spain and here we don't use inches, and I want to finde the dimensional characteristics of this angles to configure the angles we use.
Thank you very much.





RE: Angles welded in TOWER
Your welded "head" is not a term I am familiar with. Do you have a truss section consisting of single angles welded to the legs? If so you just use SAE or SAU type members and do not use bolts or holes.
As far as properties in metric units, you might write to PLS support and see if they have any tables of metric shapes. If your client or company does not have the metric tables already done, you will need to derive the properties yourself. Older versions of the AISC manual have formulas for angles. I have done a spreadsheet to generate the table data required for the PLS .ANG file.
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I have been called "A storehouse of worthless information" many times.
RE: Angles welded in TOWER
What I have is a truss section consisting of single angles welded to the legs. I have a complete table of metric shapes. The problem with this kind of tower is that in the tower fail about 115% but in the real test the tower is OK. This tower is design in 80's but now the results in TOWER is not OK. I just model like you said without bolts or holes. I wanted to ask if there was any other way to do.
Thanks
RE: Angles welded in TOWER
About the only thing you can do is report your results to your management and recommend that the tower be modified or replaced and let them make the economic decision. There is a saying, "the loss of human life will be more than offset by the cost savings". If they choose to ignore the failure and risk the potential damages, you can point to your results that predicted failure in the event the towers collapse.
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I have been called "A storehouse of worthless information" many times.
RE: Angles welded in TOWER
I have model the tower in all possibilities. And always fail in PLS-TOWER. Reduce the RLX, RLY, RLZ but always fail.
The final decission will be modify the old tower according the result of PLS-TOWER. The most important thing is the security.
Thank you very much for your help.
RE: Angles welded in TOWER
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I have been called "A storehouse of worthless information" many times.
RE: Angles welded in TOWER
In the attached file you can see the details of the tower.
RE: Angles welded in TOWER
If the towers already exist, you may be able to weld in the additional lacing and bolt in the redundants.
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I have been called "A storehouse of worthless information" many times.
RE: Angles welded in TOWER
RE: Angles welded in TOWER
RE: Angles welded in TOWER
_____________________________________
I have been called "A storehouse of worthless information" many times.
RE: Angles welded in TOWER
RE: Angles welded in TOWER
_____________________________________
I have been called "A storehouse of worthless information" many times.
RE: Angles welded in TOWER
RE: Angles welded in TOWER
If I have the leg of the firs part of body like in the drawing attached. In the angle member conectivity for the RLX, RLY, RLZ, I think should be 2/1/1. The old design was made with 2.4/1.34/1.34. If I use 2/1/1 the weight of structure is less. Am I right?
Thanks
RE: Angles welded in TOWER
To answer your question, yes the tower design will be lighter if you use the staggered bracing and 2/1/1, but I'm not sure you can justify it unless you do some testing.
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I have been called "A storehouse of worthless information" many times.
RE: Angles welded in TOWER
RE: Angles welded in TOWER
RE: Angles welded in TOWER
Thanks for all your support.
RE: Angles welded in TOWER
The legs are continuous but are usually analyzed as truss members with pinned joints. The program takes into account some bending stiffness of the legs so that it is mathematically stable. In the strictest sense, a truss member analysis of the staggered leg bracing is unstable and a normal FEA program will never solve the stiffness matrix because of the instability that you see.
Our T-Line industry is fairly unique in that we will accept occasional failure in order to put up cost effective lines. The bridge and building engineers that have to consider human occupancy would faint if they had to deal with the factors of safety we use all the time.
I have attached a marked up screen shot with a few redundants added that would stabilize the legs and allow K=1 for them.
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I have been called "A storehouse of worthless information" many times.
RE: Angles welded in TOWER
You might write to tech support at PLS and ask about that example Number 8 leg bracing factors. Also, take a look at example number 5 where the bracing ratios are 2.4/2.4/0.67 for the staggered braced legs. Example 12 also uses 2/1/1.
Like I said before, I don't use these staggered bracing patterns and I would have to ask the experts I know.
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I have been called "A storehouse of worthless information" many times.
RE: Angles welded in TOWER
I will be conservative to avoid problems.
RE: Angles welded in TOWER
The examples provided with PLS-Tower are meant to show the program functionality and some modeling concepts and are not meant to be 100% correct. I think Ex8, Ex5, and Ex12 were probably provided by clients.
If your new tower is square, I would drop the staggered leg bracing and/or add some redundants (these can be included in the PLS-Tower model now) to get the legs symmetrically braced.
_____________________________________
I have been called "A storehouse of worthless information" many times.
RE: Angles welded in TOWER
Thank you very much for your help.
RE: Angles welded in TOWER
RE: Angles welded in TOWER
http://content.asce.org/files/pdf/ETS2012PrelPrgfo...
As far as text books, I don't know of any out there. I have written a paper that is available on the PLS-CADD web site called Efficient Tower Design that you can read although it is getting old and was based on older versions of the program.
http://www.powline.com/contrib/EfficientTower.pdf
Maybe once I retire, I will write a book on transmission tower design. I could probably sell 100 copies because our industry is so specialized that there are not many more than 100 of us in the world.
You might also get a copy of the loading guide ASCE 74.
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I have been called "A storehouse of worthless information" many times.
RE: Angles welded in TOWER
As you said our industry is so specialized and there are no many documentation to learn. And here in Spain there is not many documentation because of this I am looking for in USA. If you write a book I will buy a copy sure!
I have the ASCE 74 and IEC 60826 but at this moment I don't have time to study.
RE: Angles welded in TOWER
RE: Angles welded in TOWER
The restraint code can be tricky and you have to remember which axis controls the compression.
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I have been called "A storehouse of worthless information" many times.
RE: Angles welded in TOWER
In PLS-TOWER is possible have in consideration an earthquake load? For example the tower have to support 0,4 in the three directions. How I use this in PLS-TOWER? I have read in a CIGRE document that is not necessary for a TOWER, but one company ask me if our towers support this earthquake load.
RE: Angles welded in TOWER
If you have access to some high powered FEA programs, you could model the tower in SAPS/Nastran/GTstrudl and put the mass of the conductors at the end of the insulators and find out the dynamic forcing function for an earthquake in you area and check the tower for that load. I really doubt that the earthquake load will control anything, and I would try to really discourage your client from requiring it. I think it could be done with lots of extra work, but I doubt it will be worth the extra effort.
Now you could just tell the client, "sure, our towers will withstand 0.4G in all 3 directions" and hope the big earthquake never happens. I would probably write to PLS Tech support and see how they recommend you analyze for the seismic loads.
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I have been called "A storehouse of worthless information" many times.
RE: Angles welded in TOWER
I was speaking with the client and I have said that in ASCE or IEC or ISO standars don't have seismic loads. I have explain what ASCE and IEC said and he said OK, they will think about it.
Tell the client, "sure, our tower will withstand 0.4G in all 3 directions" I have to defend the project in front of them. Is better try to persuade and don't ask for de 0.4G.
There is no way to do a load case in PLS-TOWER, I should calculate the LTV loads whit a standar (ASCE, ISO or IEC) but no one have formulation to do.
RE: Angles welded in TOWER
Take a look at ASCE 113 (if you have a copy) in section 3.1.7.1 which gives an equation for an earthquake load where you calculate an equivalent static load that is applied at the centroid. You could make a PLS-Tower load case with no wind and all factors as 1.0 and apply a joint load on a joint close to the centroid. I doubt that this load will control any members but I believe is is possible.
If you can convince the client that the earthquake performance of a tower is good, you will be better off. I have heard of only one incident where an earthquake damaged a tower. The fault line went between the tower legs and the relative foundation motion ripped the tower apart.
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I have been called "A storehouse of worthless information" many times.
RE: Angles welded in TOWER
I supose my 0.4 should be Ss or S1. Is this correct?
When it speak about Structure Earthquake loads it said lateral force (Transversal). How I apply in 3 directions?
And the last doubt, in the Eq. 3-10, W that is the dead load, could I use the maintenance load for example.
Please find the attached file.
RE: Angles welded in TOWER
Good luck;
George
_____________________________________
I have been called "A storehouse of worthless information" many times.
RE: Angles welded in TOWER
RE: Angles welded in TOWER
I believe the simple equivalent static approach will give you something to input into PLS-Tower to check the members, and I really doubt these loads will control anything. In order to do a thorough seismic analysis, you would need to model the tower in some FEA program like ANSYS and apply the earthquake forcing function and run a dynamic analysis.
_____________________________________
I have been called "A storehouse of worthless information" many times.
RE: Angles welded in TOWER
RE: Angles welded in TOWER
Thanks.
RE: Angles welded in TOWER
_____________________________________
I have been called "A storehouse of worthless information" many times.
RE: Angles welded in TOWER
RE: Angles welded in TOWER
Take a look at ASCE 10, Example 7 for a very good explanation of which code to use.
_____________________________________
I have been called "A storehouse of worthless information" many times.
RE: Angles welded in TOWER