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ill <br /> um ka. :y( 41:la-rl f 11LLEiiBc Rf ID _.._.. _ 77MILLER ru`{D P.1 <br /> JUN 05 '97 02t14PM <br /> •� • . <br /> June 5, 1997 <br /> ?. Scott Ballance <br /> • Bechtel <br /> US West Wireless Project <br /> 426 North Fairview, Room 101 <br /> �' St. Paul,MN 55104 <br /> RE: Miferbernd Mfg. Co. Antenna Monopole Structural Integrity <br /> The Millerbemd Mfg. Co. monopoles used by US West for this project meets or exceeds the <br /> requirements of EIAJTIA 222 "Structural Standards for Steel Antenna Towers and Antenna <br /> Supporting Structures" specification. This is the recognized specification for these types of <br /> towers. When designing the structure, wind&ice loading along with the number, size, height <br /> : -:, and style of mounting of the antennas are taken into account to determine the size of the <br /> structure required. The structure will have an approximate safety factor of 1.5, or in other <br /> words,will be 1.5 times stronger than it needs to be. The monopole has been designed to <br /> withstand at least 100 MPH with a 1/2"thick coating of ice on the monopole and antennas. <br /> III 0 <br /> Millerbemd Mfg. Co. only uses American-Made carbon steel(ASTM A572 or A6 7)which has <br /> a 50,000 PSI min yield. All our steel is ordered with mdl certifications to verify integrity of the <br /> material. The mill certifications are kept on file, should a copy be required at some future date. <br /> Only AWS-D1.1 "Structural Welding Code" qualified personnel will be used during the wi-ldin¢ <br /> of the structure. Weld inspections will be performed by SNT-TC-1A qualified Non-Destructive <br /> Test Personnel to verify the soundness of the welds. <br /> With the pole designed and manufactured in accordance with the above criteria, Mi lerbernd <br /> : • Mfg. Co. certifies that the monopole will not collapse. If for some reason,the wind loading <br /> exceeds the monopole carry capabilities,the pole will not collapse,but rather the top of the pole <br /> 2"' will start to bend over and the pole will begin to look ltice an upside down I. The bending wi l <br /> continue until the antennas at the top of the pole reach a position such that the wind is blowing <br /> over the antennas and not into them Once this position is reached, the monopole will stop <br /> bending and maintain that position. For the bending to happen, the wind would have to reach <br /> over 175 MPH and be maintained for a length of time. <br /> • <br /> MILLERBERND MANUFACTURING COMPANY• P.O. BOX 98 • W/NSTED, MINNESOTA 55395 <br /> PHONE(320) 485-2111 • FAX(320) 485-4420 <br />