Greetings
I am halfway into erecting my first tower. It consists of two commercial
6,5 meter (length) triangular, 450 mm (diameter) galvanized steel sections
giving me 13 meters of height plus another 3 meters of a 6 meter pole above
the top bearing. Low by USA standards (I think) but 1 meter above the legal
(without planning permission) height in South Africa :) The base consists of
two T - hinge sections where one T - section bolts onto a
heavy-duty cage set into 1 square meter of concrete. The other T - section
bolts via two hinges to the base T - section on which the three legs of the
tower slides and gets bolted into three (50 mm diameter, 5 mm thickness and
200 mm length) tubes welded to the T - section.
I have raised the possibility of the three steel tubes (45 mm diameter,)
that is welded to the one T - section onto which the three tower legs slide,
failing at the weld. The welding was done by a professional and is about
1.5 cm around the tubing. I am being told not to confuse bulk with strength
and that thicker steel will rather add weight than strength. Also that the
triangular configuration will tend to balance the forces and weight of the
tower. Still these three tubes will be taking all of the weight of the
tower and still worries me as a weak point in the process.
- Can someone explain to me the forces of gravity and wind involved in the
case of a triangular tower and where the stress points are? Will the base
tubes take these stresses (laterally and downwards)? I would like not to
have to guy the tower as it is not very high, am I being silly with such an
idea.
The base T - section hinges right at the bottom about 100 mm above the
concrete, the bolts supplied for the hinges were 20 mm diameter for a 30 mm
hole.
This would result in the T -section being able to laterally move in the
hinges if the tower is moving due to wind etc. I have acquired high-tension
steel bolts that fit tightly into the holes and now prevents any lateral
movement.
- Would there be a reason for allowing the movement or am I correct in my
assumption that such movement will put unnecessary strain on the bottom T -
sections and hinges. Some advice given says that a tower should be allowed
to have some movement?
Thank you very much
Wynand
ZS6ARF
zs6arf@telkomsa.net
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