Abstract
A line of transmission towers extending from Anchorage to Fairbanks ,
Alaska has been designed using a highly flexible X frame. A s upporting
structure which can "give " and redistribute the heavy wind and ice loading
has long been recognized to be efficient in this e nvironment. This
structure has posed a difficult analytical problem because it has a
pinned base and is guyed with a load balancing yoke on each side. The
configuration of the legs and the s lende r members which are typically
used , make the structure susceptible to buckling. Despite these problems ,
the structure has a habit of standing up without its required analytical
foundation .
Because of the problems associated with the structure , it was decided
to s tudy the tower ' s behavior before a detailed analysis was required
for bidding . The Union Metal Manufacturing Company felt that a
nonlinear analysis of this structure would add to the credibility of their
proposal to fabricate these towers . Some staff members had some previous
experience with this type of tower and had seen full scale tests . They
were able to add some insight in setting up the finite element model.
Two approaches using ANSYS were considered and compared to verify
the results. The first was a large displacement analysis with stress
stiffening and initial strain. The second was a slow dynamics ana1ysis
to handle the ins tabilities due to the guyed support system . Both of
these approaches produced reasonable results which will be discussed in
this paper .
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