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"'�'�.r�r�► ViIIVCl3111VI •IM.011s171"cxtenSIon <br /> • <br /> Teleceanmunications Center <br /> WHA Radio&Television <br /> 821 University Avenue <br /> Madison,Wisconsin 53706 <br /> (608)263-3970/263-2121 " <br /> June 18, 1984 <br /> MEMORANDUM <br /> TO: ANN MILLER <br /> FROM: DON BORCHERT <br /> SUBJECT: IMPACT AREA RELATED TO TALL TOWER FAILURE <br /> This memo refers to guyed tall towers only . . Tall towers are <br /> usually considered to be those that are more than 1000 feet above <br /> ground level . I think it is important to say that it is very rare <br /> for tall towers to structurally fail and fall to the ground. While <br /> no specific study has been made, it appears as if the failure rate <br /> for all causes is less than 1%. In Wisconsin there are at least 15 <br /> tall towers, some of which have been standing for more than 25 years. <br /> I can only recall one tower failure and that was in Rhinelander. The <br /> tower was hit by an aircraft. Fact is towers withstand severe storms <br /> very well due to minimum wind loading characteristics and very con- <br /> servative design. Tall towers usually remain in tact when buildings <br /> all around them sustain damage. Another important fact is that 90% <br /> of the towers that fail structurally fall within an area of 40% of <br /> their total height and none fall outside of the perimeter of their <br /> outer guying foundations. <br /> /341-0 /3044,14. <br /> UW-Extension provides equal opportunities in employment and programming. <br />