FWIW I am not an engineer nor even a TOWER TECH but I might toss in a tidbit.
Round pipe filled with concrete does add more bending resistance - but it will
snap like a pretzel when the concrete gets its first crack in it which will
happen quite easily when it is flexed any at all. Concrete does not like to
bend period. If you
were to ram it full of rebar you might gain some more strength but it will
still crack. Where ever the crack occurs, which will be right at ground level,
the pipe will hold for a period and then the entire thing will break off
immediately without warning. I feel like I would rather have it empty where I
could see if it was bending any than with cement where you would have no
warning. Steve has given you the best advice on the H beam or I beam for
strength. On the other hand - weren't you only going 40 foot to begin with?
Dave / NØATH
I'll second the observations made by W8JI - you've got the wrong
material. I've always gone by the 60/40 rule for elevated guys - 40% in the
60% sticking up so you've got way too much sticking out with too little bending
resistance. (Remember your high school physics? If you have X force at one
foot, you'll have 16X force with a 16' lever arm.)
BTW even if you fill the round pipe with concrete, that doesn't really
add any more bending resistance to the pipe.
You need to pow-wow with an enginer to get the design details worked out.
TOWER TECH --
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