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COMM TWR 40~ 359 5856 <br /> <br />COMM TWR <br /> <br />M0.760 <br /> AUG ~5 <br /> <br /> P.1/3 <br />~98 OI:16PM <br /> <br />Valmont Industries, Inc. · West Highway 275 · P.O. Box :358 <br /> Vatiey, Nebraska 68064-0358 U.S.A. · (402) 359-2201 <br /> August 25, 1998 <br /> <br />US West Wireless, LLC <br />426 North Fairview Avenue <br />Suite 101 <br />St. Paul, MN 55104 <br /> <br />Attention: Mr. Adrian Sehottroff <br /> <br /> Subject: Failure Modes for Poles and a D~cription of the Design Criteria <br /> US West Wireless Site: SCLO05 <br /> Valmoat Order No. 17453-98 <br /> <br />Dear Mr. Schottroff: <br />I have been asked to write to you about the mode of failure for pole type structures used to <br />support wireless phone antennas and equipment, and give some information to allow you to <br />judge how remote the chances of failure occurring would be. I think it would be appropriate w <br />start off by a brief description of the design criteria'that is typically used. <br />The pol:~s Valmont supplies are designed in accordance with E.I,A.FLLA. 2:22 Revision F <br />entitled "Structural Standards for Steel Antenna Towers and Antenna Supporting Structures." <br />Tkis is an approved A.N.S.L standard that has dealt with-the design of la, ce type structures for a <br />number of years. Revision E is the first version that goes into extensive detail about the design <br />of pole type structures. The provisions of the standard have, as their foundation, provisions of <br />other raxtionally known specifications and standards that have a long history of reliability. This <br />history should be of interest to you considering the hundreds of thousands (if not millions) of <br />sites throughout the United States which have structures designed with concepts spelled out in <br />publications like "The Design of Steel Transmission Pole Structures" (published by A.S.C.E.), <br />and "Standard Specifications for Structural Supports for Highway Signs, Luminaries and Traffic <br />Signals" (published by A.A.S.H.T.O.). Many of the concepts used to design poles in these two <br />publications are included in the EZ.A2T.I.A. 222 Revision F Standard. <br /> The E.I.A./T.LA. 22:2 Revision F requirements dictat~ a basic design wind speed. The wind <br /> speed :o be used depends on the location of the site within the state. Vahnont's policy is w use <br /> the wind loading in E.LA./TiA. 2:22 as a minimum loading. Statistically, the wind speed listed <br /> in E.I.A./T.LA. :222 has been determined tn be that wind which has an average reoccurrence of <br /> 50 years. This wind is also o''fastest mile" wind which means that it is the average velocity of a <br /> mile wind passing a point. For example, a 70 mph average fastest mile wind would take 51 <br /> seconds to pass a point. This standard "fastest mile" wind is customized with factors that apply <br /> tn the particular installation. There is a 1.69 gust response factor imposed to account for sudden <br /> <br />EXHIBIT D <br /> <br /> <br />