huangyhg

town square christmas tree
don't know how i got selected for this but our agency is donating an approx. 40' tall christmas tree for the town square. the area were the tree is to be placed is exposed to large winds. i don't know have any information on soil characteristics.
my first thought of how to support the tree was to drill a large hole (approx 1' great dia than base of tree) insert a culvert of the same diameter into the hole place the trunk into the hole and fill with sand/concrete.
i have a couple of issues with this plan.
1) how deep to drill in culvert to resist overturning
2) how far to insert trunk into culvert
any thoughts or other solutions would be greatly appreciated
talk to your power company engineering group they have a lot of expierince putting wood poles in the ground. they should be able to give you good advice
i would probably use a steel tube of sufficient diameter and thickness with bolts located top and bottom for 'squaring' the tree. the tube should have an equivalent strength of the tree and the bolts accordingly. bolt placement may be 6 or 8 times the tree diameter. you might see if you can enlist a local engineer to do a pro bono... then you have to design the base..
dik
i would think that whatever you do, you may want to use deadman/guywires to anchor it
try calling rockefeller center - they have a lot of experience with christmas trees (212)632-6797.
as i recall, the tree is set above grade and surrounded with soil.
my hat's off to you and your town for calling it a christmas tree and not a holiday tree, winter tree, etc.
40' tall tree? - easy erect the barricades 50' away!
on a more serious note, you probably don't know the strength of the tree trunk or the wind speed local to where the tree grew up. it is therefore risky to rely on the trunk for total stability.
while i've never designed such systems, the ones i've seen have guy wires hidden within the branches and fixed to the ground below. i'd guess they fix the the trunk at about mid height.
hope that is of some help.
you may want to consider talking to an overhead sign structure producer since they make highway signs that resist the same loading. you could also talk to your local highway department. the florida department of transportation has a mathcad spreadsheet for designing o/h sign structure supports, which is available on the web if you have a current version of mathcad. i suspect you will need a soil boring unless you want to overkill the design. also consider that you want to be able to water the tree to prevent fire.

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