HomeMy WebLinkAbout1127 W. PROSPECT RD., WIRELESS TELECOMMUNICATION FACILITY - FDP - FDP160041 - SUBMITTAL DOCUMENTS - ROUND 1 - WTE / WTF INFORMATIONISE, Incorporated
Structural Engineers Telecommunications & Industrial Design
PO Box 50039 x Phoenix, Arizona x 85076 x Office: (602) 403-8614 x Fax: (623) 321-1283 x www.ISE-INC.biz
September 27, 2016
Layla Brown
Larson Camouflage
1501 S. Euclid Avenue
Tucson, AZ 85713
Subject: Monopole Fall Zone Design
Atlas Towers – 1127 W. Prospect Rd
Ms. Brown,
The steel mono-pole structure proposed for the subject site will be designed in accordance with the
Telecommunications Industries Association Standard TIA-222-G, “Structural Standard for Antenna
Supporting Structures and Antennas”. The TIA-222-G standard is a Reference Standard of the
2012 IBC. Pursuant to the 2012 IBC and the TIA-222-G, the pole will be designed for the
designated wind speed cited for the specific site location.
Per the TIA-222-G Standard, the pole and foundation design incorporate the same Factors of
Safety specified by the 2012 IBC, the American Institute of Steel Construction (AISC), and the
American Concrete Institute (ACI). The Safety Factors, as applied, yield a design that has 25%
greater strength than that required for the actual design forces; the loads would have to exceed
125% of the design forces to reach the theoretical failure loading.
The pole is designed with a “fuse flange” at 15’ below the top of the tower. This means that the
flange bolts for the top 15’ pole section have a design capacity usage of approximately 96% at the
maximum design load condition. The remaining pole sections, base plate, and anchor bolts are
designed to resist considerably more than the design wind. This design process forces an unlikely
"failure" to occur in the top pole section before any other pole sections or components.
When overstressed, steel does not suddenly “break”, it bends and buckles. In the highly unlikely
event that the pole should collapse, the flange bolts would elongate and the top pole section would
possibly bend over and, if the bolts ruptured, this upper portion would then swing down and hang
from this level or, at worst, break off resulting in a fall radius of approximately the length of the top
section. If the upper pole section is no longer upright, wind forces to the rest of the tower and
resulting overstress will be significantly reduced making further collapse unlikely.
The proposed pole for this site will be designed by a licensed engineer with a fall radius that is less
than or equal to the shortest distance between the pole and the nearest property line.
If there are any questions regarding this issue, please feel free to give me a call.
Sincerely,
Glen L, Hunt III, MS, PE, SE
Principal Engineer