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2 Story 24" Pier Hmmm Maybe For An 8" SCT

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Posted by Rick Crockett on September 12, 2000 05:36:01 UTC

Hi guys:

Bob is definately correct but even that may not be enough.

Funny I was experimenting with a pier Saturday after we left the TM class Bob. Mass can actually make a pier vibrate more. It may be more resistant to deflection and the period of oscillation much lower but it takes a l o n g time to dampen.

I am fairly convinced that a 1/2" wall 24" steel pipe casing would be better than filled with concrete(except at the bottom) and the steel rods seem to help little. Concrete can be prestressed and that seems to stiffen it up. I would investigate this further before assuming your pier will do the trick.

Two rods 120 apart on the south side of the pier and extending down and outward at a 20 to 30 angle passing through but not touching the wall and anchored to the ground would probably work best. Stress the pier with the rods then set your latitude. A 12" pier done this way should be many times stiffer than just a poured 24". If you can find a structural engineer challenge him to do the calcs. He most likely will think an 8" pier will do but then tell him that you need to maintain deflections of less than 1/10th sec. of arc. with 20 to 100lbs of perpendicular load at the top end. He may be so embarassed as to do the calcs and engineering for free.

Then tell us, He He He!

Cheers,
-Rick

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