H Pole Foundation (Overturning)

[Albert20]

Hello there

I need a push in the right direction to allow me to look at the foundation of a power line H pole assembly. The structure is an intermediate structure and as such is mostly subject to a lateral wind load acting on the conductors and poles. I've attached a drawing for reference.

I know that if the structure is cross braced the main loads are uplift on one leg and bearing on the other (similar to a broad based transmission tower with individual footings). However, what's throwing me here is the fact that there is no cross bracing between the poles above ground but yet the poles are connected and braced below ground.

Does this mean that the main foundation loads are still uplift and bearing on the left and right legs respectively (as pictured).

Many thanks for your help.

 

[MikeE55]

I would treat this as each post carrying the same load and being fixed base. You don't have enough load transfer between the posts to consider tension on one and compression on the other.

 

[paddingtongreen]

Is this a standard for somebody? it looks expensive, lots of excavation and carefully tamped backfill. I suspect that the bracing is just to keep them aligned during erection, so I agree with MikeE55. Considering the multiplier (height of pole above brace multiplied by the wire wind load, divided by the depth of the brace) the connections would have to be more than single bolt.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[Albert20]

Thanks for taking the time to reply. Yes, its a standard design and it requires a big excavation! Variations on this design are used at different voltage levels.

If I'm understanding this correctly, treat each pole as having an independent fixed base foundation and design this to resist one pole's bending moment load? So, basically the above design will have twice the capacity of a single pole.

Apologies if these questions seem a bit basic, I've kinda been thrown in the deep end...

 

[paddingtongreen]

Albert20, this is one where, for your own understanding, you should work it both ways just to see the ramifications. Sometimes you just have to talk to a structure, you have to ask it questions. Suppose it was intended that the bracing do the work, pick an example and see what the loads are.

As to loads, you do have the wire loads and the wind on both poles to share between them, in the separate pole case.

Michael.
Timing has a lot to do with the outcome of a rain dance.