04-27-1999 Council Agenda - Laserfiche WebLink

Home Browse Search

25.1998"— 2 :26PM COMM TWR 402 359 5856 ve VALMONT. MICROFI.ECT COMM MR Valmont Industries. Inc. • West Highway 275 • P.O. Sox 358 Valley. Nebraska 680640358 U.S.A. • (402) 359 -2201 August 25, 1998 US West Wireless, LLC 426 North Fairview Avenue Suite 101 St Paul, MN 55104 Attention: Mr. Adrian Schottroff Subject Failure Modes for Poles and a Description of the Design Criteria US West Wireless Site: SCL005 Valmont Order No. 17453 -98 NO.760 P.1/3 AUG 25 '98 01:16PM Dear Mr. Schottrof£ I have been asked to write to you about the mode of failure for pole type structures used to support wireless phone antennas and equipment, and give some information to allow you to judge how remote the chances of failure occurring would be. I think it would be appropriate to start off by a brief description of the design criteria that is typically used. The pairs Valmont supplies are designed in accordance with E.I.AJT.I.A.g Sirictures." entitled "Structural Standards for Steel Antenna Towers and Antenna Supporting This is an approved A.N.S.I. standard that has dealt with the design of lattice type structures for a number of years. Revision E is the first version that goes into extensive detail about the design of pole type structures. The provisions of the standard have, as their foundation, provisions of other nationally known specification and standards that have a long history of reliability. This history should be of interest to you considering the hundreds ofthousands swill d out sites throughout the United States which have structures designed (published by A S.C.t in. publications like "'The Design of Steel Transmission for E Structures" (p fished Luminaries and Traffic and "Standard Specifications for Structural Supports used to design poles in these two Signals" (published by A.A.SILT.O.). Many of the concepts publications are included in the E.LA./TS.A. 222 Revision F Standard. The E.I.AJT.LA. 222 Revision F requirements dictate a basic wind spee police w nduse speed to be used depends on the location of the site within Statistically, the wind y is to used the wind loading in E.LA.IT.I.A. 222 as a minimum loading reoccurrence dsp listed to in E3.AJT.I.A. 222 has been determined to be that wind which has an average of 50 years. This wind is also a "fastest mile" wind which means that it is the average velocity of a mile wind passing a point. For example, a 70 mph average fastest mile wind would take 51 "fastest mile" wind is customized with factors that apply seconds the particular to pass la a point This standard response factor imposed to account for sudden to the particular installation. There is a 1.69 gust Page 37