Pat,
Regarding the following message:
>>I am musing over a sketch of a guyed tower, plan view, and wonder
how the positioning of guy anchor points changes with sloped ground. Does
one try to keep constant angle by all guys to the tower, by changing the anchor
radius, or do you keep a constant distance to the anchor point, with the
resulting different vertical angles? Also, if the ground rises a
significant amount on one side, then for a 2 level guy system, the top
guy, and the middle guy, assuming they would converge to a single point
anchor, on level ground, intesect the real world sloping
ground at two points that have significant spacing between them. In this
instance, with sloped ground, do you anchor the top and middle guys at 2
locations?
If the angles of different guys at, say, the center guy point on the
tower, are different, and the guys are tensioned equally, there will be
different horizontal and vertical force components attributable to each
guy.....How do you deal with sloped ground when guying?
K1IR: I believe that your objective will be to create a horizontal RESULTANT
FORCE at the
attachment point on the tower for each guy which is equal to the RESULTANT
created when using the recommended anchor point. You will first decide on a
location
for your anchor on the ground. This point will be plus/minus in elevation and
distance
from the recommended standard location. Next, you will use your trig to
calculate
the horizontal components of force at each attachment point when the
anchor is at the recommended position. The inputs to your calculation are the
standard angles and guy tension. You will solve for new guy wire tensions
using your proposed angles from the ground and the required horizontal force we
just
calculated. Finally, you'll calculate the angle that the rod needs to be at as
it comes out
of the ground. This will be the resultant of the combined guy wire force
vectors at the
anchor point on the ground.
The result of this will be that guy wires anchored at a lower elevation and the
same distance
from the tower as in manufacturer's recommended anchor placement will have to be
tighter, and the rod angle will be higher. The wires anchored at this location
will
contribute more compressive force on the tower than the other wires. You will
also need a
bigger block of concrete in this case, since there is more guy tension.
If you have to put the guy anchor at a lower elevation, it's a good idea to
move it further
from the tower. This helps you balance the horizontal and compressive forces
with the other
guy wires.
As you bring the anchor point lower and closer to the base, the horizontal
forces become
more and more difficult to control. Until it all falls down.
Jim K1IR
ps I'm an EE and an MBA, not and ME or a PE! But I think this still makes sense.
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