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<br /> ' Valm,~nt Indue-tries, Inc. · We~t Highway 275 · RO. Box 358. Valley, Nebraska 68064-0358 U.S.A.· (402) 359~2201
<br />changes in wind s[~ ~xf, a height coefficient to accoum for .inmc ,as,*ing wind sp~ed with h~igh~, and
<br />~ exposure coefficient m account (to some degree) the ten-alu effects.
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<br />~nne Ioads generated by this wind and'th~ v/eight of the memh::.~ (along with any ice een~idered)
<br />~z~ then used to siz~ members of the pole. '/~nere is at least a25% factor of safety r~u/:ed under
<br />Rose conditions. ~'.'.*~ assumes thai the ~,:':'nd blowing from tho worst possible dircctL, n. Some
<br />dircction~ arc wor-~ ::han others, depcndi.~ on the equipment.a~;?ched to the pole, t' ~
<br />arrangement, and fl' '~ orientation. The -~-~,h~c' must exceed all o?~' estimates for magni~u~,
<br />duration, be at tL.~ ',. ~n~ orientation an~ ~:,e.,come tho fa~u~r ~z safety. Let us assume. ~h~t a pole
<br />' ,. Iocal buckling-'
<br />c,.:~,omes overlo.'..~!' ' The typical cons~',cnc~ ofth;~ overlc ~ :~ is" '
<br />relatively small ~- .'~[Jn of thc shaft d[.,~or[~ and "k/nks" rise s~..:L This does not cause, a free
<br />.[,~lling pole. A:;'"'"., 'ri..; buckle, the cross ~c~,;.fon of the pole ie ~pah!e of carrying the
<br />ve~cal (weight) i, 2 and a substan~.! i~mdon of'the loadtb~- ~used the buclding~ ~ite pole is
<br />l~el¥, however, ~,, be dut of plumb. 'Ii£;.; may be ~omcwhsc d-~matie and the hue!dca s¢c~on
<br />:hould be repla~"
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<br />There are 3 mcr"." .isms whfch prove~::, g.~ polo from a free frq ::?/pc failure.. Firsfi zz the pole
<br />distorts this disto~ca may relieve the ~.oud f,-om the pole ei/h~.: b~-.ori~nting the po!~
<br />favorably in thc- !l~d or, ifbuckNng h~c o ',,~*am-ed, by reduc,~-~ 2;'~b.e moment arm ef~,:, rand
<br />force. The second ~aechan~m involve~ a ~,cllstribution offi..~ ~:¢ss in the pole ef:~' buckIing
<br />toward the rernaL'~g portion or the cr~s~ sect/on that b~s tr~c~-d capacity. The thkd
<br />phenomenon cud/,,are important, is tho nature of the force b~:ng spplied. We e×pe~t the wind to
<br />produce this for~, A wind that wouk, ea,:se a buckle would be larger th_an the basi.~ w~nd speed,
<br />the gust factor, and ~he factor of safe~/co..'nbined. A gust wm,.Ic~ soon dissipate an~ a~:~r this
<br />peak wiiad is gone, the stress in tho pole would be redueect POles are flera~Ie, forgivff~g
<br />structures wMch are not generally suscepU~ble tn damage by impact loads such as s wind gust or
<br />earthquake shocks. It takes some time ~or the entire stnmttms to "see" the impact loading. Even
<br />after a local buckle, the pole b,~ siguificant capacity. It is this capacity along with the transitory
<br />namm of the loading that prevent~ a pole from "falling over".
<br />
<br />Pole design and testing have provided tlm public with ~ very reliable product. Poles have gone
<br />through extensive full scale testing, resulting in a history of being extremely reliable. The public
<br />I think, h~ been served well. Yalmant has provided strnctur~ that have performed well
<br />during the ear'thqu~ fr, CalL~ornL~ the hurricanes in the South, snd a number of
<br />tornadoes, To r~ L*nowled~e, ~almont l~s never experienced an in service ~a~uro ora
<br />communication pole due to weather Induced overloading, e~en though, as in the c~ses of
<br />l:rurrtcane Hugo and Hurricane Andrew, the wind speeds may have exceeded the design
<br />wind speed.
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