How to overcome the moment at the base of a footing of a lamp post

[structcivi]

It is stadium lamp post and the moment at the foundation level is about 5000kNm. So how to overcome the uplift force generated? Also there are anchor bolts in 20 numbers in a circular arrangement for a depth of 3000mm.

 

[msquared48]

Either an augercast concrete pile or a large concrete spread footing.

Mike McCann
MMC Engineering

 

[hokie66]

I don't think a single pile is going to do it. A spread footing will work if the soil conditions are adequate. If not, a group of compression/tension piles, either precast or bored piers, with a big pile cap, would be required.

 

[rowingengineer]

Maybe not a solid pile but a concrete cyclinder gets used for wind farms. If you have rock, maybe rock anchors with hokie's solution of a pile cap/footing.

3000mm seems deep for the bolts, I would suggest the bolts be bolted to a ring plate at the bottom to reduce this requirement for depth.

Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that them like it

 

[structuresguy]

I have done stadium light poles before, as well as some highway high mast lighting. They have all been done with a single large diameter drilled pier. The diameter can get quite large, 5 to 6 feet in diameter is not uncommon. The depth is governed by the soil conditions, and the diameter of the pier.

 

[structuresguy]

Just out of curiosity, can you describe the pole and light fixture a bit. That is a very high moment (if my conversion to imperial is correct). That is much higher than I have seen from stadium poles that I have done. Mine have been in the range of 100 ft high, with fixtures that have 75 SF tributary area at the top.

 

[structcivi]

This is a light post that is used in day and night cricket matches. Height is about 45m.

 

[hokie66]

These are a lot higher than yours, but according to the article, they used a group of four bored piers under each tower.

http://www.mcg.org.au/The MCG Stadium/Facts and Figures/Light Towers.aspx