pier design question

[muletopia]

Some time ago the most informative thread

http://www.iceinspace.com.au/forum/showthread.php?t=111597&page=2

gave insight into pier design.

The nett conclusion was that large diameter steel pipes with gussets as specified by Avandonk are best.
The main unresolved question is the reflection of vertical vibrations form the mount back into the mount at the top of the massive pier.

My pier will be 4 feet of 9 inch diameter 10mm wall thickness steel pipe. The gussets are planned to be 3 feet tall.

My neighbour, who is fabricating the pier and has so far cut out the 25 mm thick base plate and drilled the holes as specified by Avandonk, has volunteered that he can machine an internal taper in the pipe. The taper to start at the top of the gussets and reduce the wall thickness to 5 mm at the top of the pier.

My questions are:-
Is this taper likely to reduce the reflection of vertical vibrations?
Is this taper likely to introduce other unwelcome dynamic effects?

Chris

[Paul Haese]

Don't bother with the taper. The thick wall thickness will help.

[muletopia]

Thanks Paul,
No taper will be machined.
The concrete mass was poured this morning, it set out to be one cubic metre but delays and bailing out after rain caused this to expand to 1.3 cubic metres, ah well a bigger bill will come. When the pier is on the pad I will recount how and problems encountered in a new thread.
Cheers
Chris