How to dimension a foundation for a lamppost?

[konrad3]

Hello, I am going to cast a foundation for a cast-iron lamppost, weighing about 100 kg. The base is about 32 cm in diameter, and there's a lot of sand in the ground. I'm planning to cast threaded rods to bolt down the posts. The question is, how large do these foundations need to be?

 

[scorp1on]

If one were to perform a calculation according to all the rules of the art, one should check the base pressure under the foundation, risk of sliding, and overturning (when the wind pushes from the side). You should verify that the soil can handle the pressure and that you have a sufficiently large foundation so that the anchor bolts have adequate anchorage. You should also calculate the crack reinforcement in the foundation...

How tall is the pole?

 

[konrad3]

The pole is 3.20m high. Father-in-law also says that the foundation should be 10-15cm outside the bolts. Since I plan to dig 1m down and the form will then be about 45x45cm, it will weigh between 400-500kg. To me, that feels like a lot?

 

[Taxture]

https://www.ljustema.se/stolpar-fun...MIqpSH_ufA8AIVo4BQBh2plgnsEAQYHCABEgJgcPD_BwE

57kg for a 4-meter light pole...
Perhaps a little guidance?

 

[Fulkemisten]

It is not the weight of the foundation but how well the quality is made that holds it in place that matters. Indirectly, a larger foundation becomes heavier, and this of course matters.