Why would there be no grouting in this case? 1

[kingnero]

See attached pics, approx. 100 ft pole for overhead electrical lines with a circular baseplate mounted on threaded studs.
Doesn't look that old, however the installation has been in service for a few years, so unlikely that grouting is still planned to do.
There is no cable (apart from a ground strap) that goes from the pole to the concrete foundation (even though it looks like that).

What could be the reason grouting is not done?

 

[Tomfh]

It’s common in some industries to support column baseplates on levelling nuts, with no grout. There are some additional checks required regarding plate bending, bolt bending, etc.

There’s been a number of threads on it before. Example:

https://www.eng-tips.com/viewthread.cfm?qid=451445

 

[STpipe]

The general thought on this is to leave the base ungrouted to prevent any accumulation of moisture and provide better corrosion protection.

 

[MillR]

It also moves the reaction couple further apart. If you grout, the compression half of the moment couple moves in from the bolts. With no grout, the bolt has to take the tension and compression. None of the base plates for utlities in FL are grouted, but they are in CA, CO, etc.

 

[Boiler106]

i have also seen grouted base plates under light poles in downtown cleveland (US) where the grout has cracked and separated, reducing the bearing area (and no setting nuts). The pole would move considerably in the wind.

 

[BridgeSmith]

Grout would serve no structural purpose, since the steel bolts are much stiffer than the grout, so nearly all the load would still go to the bolts. This is common for poles for several reasons, but the biggest 2 are that the axial load is very small relative to the moment, so the compression stress is not significantly more than the tension stress, and geometric control (getting the pole exactly plumb) is necessary for a proper installation.

 

[canwesteng]

How are the bolts much stiffer than the grout? Elastic modulus of at most 10 times that of the grout, but the area of the grout is going to more than ten times the area of the bolts in most cases.

 

[JStephen]

Most of them that I see have fatter bolts and less of a gap to the ground, so those bolts look a bit spindly.
Another common construction around here (north Texas) just has the pole itself embedded in the concrete. I don't know how they're actually detailed, or whether there are bolts below ground or what.

 

[BridgeSmith]

Elastic modulus of at most 10 times that of the grout, but the area of the grout is going to more than ten times the area of the bolts in most cases.

That's a good point. You're probably right. I guess it's mostly that grout is not needed because the design compression stress on the bolts is only slightly greater than the design tension, and each of the bolts have to be designed for both. For our high mast light towers, the compression stress in the bolts due to axial load is about 0.4 ksi. I'm guessing the loading is similar for the transmission tower pictured.

 

[jhnblgr]

This design is pretty common due to corrosion for pole structures. Relationship between bolt diameter is used for determining max stand-off. Washers used are also key since the nut isn’t much larger than the bolt holes, standard bolt holes are recommended.

Design guidance

https://www.towernx.com/downloads/Technical_Manual_MP_BasePL.pdf

Issue is typically these structures fail in fatigue at the base plate to post connection due to stress concentrations.

Looking at this structure the edge distance is too small likely and the anchors would most likely fail first.

 

[kingnero]

Thanks to all for your interesting replies. Being mostly mechanical/welding, I've learned again something new (for me) here.