How strong is that concrete pier?
Posted 01 April 2013 - 12:19 PM
Posted 01 April 2013 - 12:55 PM
It's a good choice because:
- It has high mass (due to it being cheap and thus solid)
- It has high stiffness (due to diameter, mostly)
- It has a high damping coefficient (5-10 times that of steel or aluminum)
Posted 01 April 2013 - 08:54 PM
If you do the base right it shouldn't move. 12 inch diameter was
plenty beefy for my AP900.
Posted 01 April 2013 - 09:03 PM
Posted 01 April 2013 - 10:11 PM
My 12 inch diameter pier is literally rock solid. Vibration, what's that?
Posted 01 April 2013 - 10:27 PM
A concrete pier needs a solid footing below the frost line so that it won't shift with the seasons. Some rebar inside won't hurt.
What is the need for rebar? Will the pier be stressed in tension?
Posted 02 April 2013 - 12:18 PM
Check with an engineering textbook for formulas to calculate the amount of bending. Steel rebar reinforcing of a concrete post should decrease the bending because the steel bars will need to expand and compress as the post bends. (This assumes proper placement of the rebar.)
Concrete beams that are supported on both ends and are expected to support a load in the middle (ie bridge supports) always have steel reinforcement. Concrete is much stronger when compressed which is why pretensioned steel cables are used in bridge construction.
Posted 02 April 2013 - 02:26 PM
Concrete will bend but unless you are mounting a monster scope, don't worry about it. Pour and enjoy.