Electrical Substation Gantry Structure 3

[KillBill7]

I hope this is the right forum to ask this question...... I am designing terminal gantry structure for the substation where incoming transmission line will terminate. I do have max tension data from the client which is 1500lbs per phase, I do know the deterministic weather loading criteria (combined wind & ice loads) for the the area from the CSA standard. However,I am missing the reliabilty based loading criteria (heavy wind and rime ice)for the area. I know the max tension so I know worst case longitudinal load, however, for worst case transverse and vertical loads do I need to know reliability based loading for the area?
In our company setup, electrical does the main transmission line design with the help of civil/structural. So electrical provides the joint loads (loading tree) to structural and then they design the gantry structure based on the loading requirements. My other question for structural engineers is do you design the gantry structures on the basis on pulling force only or do you also take into account transverse and vertical loads.

Curious to know your thoughts on this.

 

[oldestguy]

For what it may be worth, in my experience I have seen two such transmission lines fail, not the structure or cables, but the foundation is pulled out of the ground. Make sure the engineers have an experienced geotech on this design.

 

[STrctPono]

I can't help you in regards to the loads on the conductors but I can tell you that when I have been involved with the design of transmission line poles/towers, the Electrical Engineer typically works with the power company to figure out the tension and sage of the conductor. The Electrical also calculates the vertical loads and transverse loads due to self weight, wind, ice, etc. Those loads are provided to me (The Structural) as they occur on the structure. The structure has additional wind loads that it needs to be designed for which the Structural Engineer will calculate and combine as necessary with the conductor loads. Structural typically then works with Geotechnical to size the foundation.

 

[r13]

Down to the basic, you shall provide the known design loads (pull, gravity and transverse), and the reference of design criteria that need to be followed. Yes, we do consider all, but since the transmission line is not well covered under typical structural codes, it will be in your best interest to be as clear as possible, rather than letting us do our own research, as it is usually time consuming, yet non-productive.

 

[Lomarandil]

Answering the original question, yes, it is usually necessary to know vertical and transverse loading, not only the line tensions, in order to design a dead-end structure.

It is dependent on the size and geometry of your dead end, but there is typically at least some interaction between the applied loads, even when line loads drive the design.

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just call me Lo.

 

[KillBill7]

Thank you guys for the input. I think I got my answer.