The 1ft by 6ft cylindrical pier you suggest will weigh only 627 lbs. Imagine
the wind blowing perpendicular the tilt up hinge piers. Now the only thing
resisting your tower from tipping over that 627lb pier. The wind forces on
the tower will cause a upward vertical load on that pier and attempt to pull
it out of the ground. Given you also want to add a spiral stair case etc,
you are significantly increasing wind load. Having gone thought all the
calculation the structural engineer did for my 45 ft tower, and that
calculation specified much more concrete that you are suggesting for your
much higher wind load tower.
I strongly suggest you seek the help of a structural engineer which this
installation.
Kirby - AF6OP
> Since in its new life this tower base is not holding up a 100 ft heavy
> duty tower what is a reasonable pier size and depth? I can auger up
> to 12 inch diameter holes up to nearly 6 ft deep with my equipment,
> Alternatively I have a ride on trencher (like a backhoe but self
> propelled not on the back of a tractor) that can dig a 13 inch wide
> trench down to 7 ft or so. I could block off part of the trench and
> back fill prior to the pour and have a more or less rectangular pier
> about 13 by xx inches up to about 7 ft deep but this is more effort and
pending your input may not be required.
>
> I intend to add a spiral (triangular) staircase around the outside of
> the tower to access the observation/work platform that I will install
> at the 40 ft level. This deck will be larger than the tower's triangle
> dimensions at the top (40 ft level) and so will be cantilevered. I
> will not extend this deck so wide as to extend beyond a vertical
> projection of the piers thus not risk a tip-over event due to any load
> of sightseers. I want to install an automated crank-up tower inside
> this tower such that when fully lowered you can stand on the platform
> and access the lowest antenna on the tube coming out of the center of the
top of the crank-up tower.
>
> Any thoughts?
>
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|