HomeMy WebLinkAboutUP16-0005 - Horizon Fall Letter CertifiedDecember 12, 2014
Ms. Suzie Densmore
Horizon Tower, LLC
117 Town & Country Dr., Suite A
Danville, CA 94526
RE: Proposed 80’ Sabre Monopine for Oroville, CA
Dear Ms. Densmore,
Upon receipt of order, we propose to design and supply the above referenced Sabre monopine for
a Basic Wind Speed of 85 mph in accordance with the Telecommunications Industry Association
Standard ANSI/TIA-222-G, “Structural Standard for Antenna Supporting Structures and Antennas”.
When designed according to this standard, the wind pressures and steel strength capacities include
several safety factors, resulting in an overall minimum safety factor of 25%. Therefore, it is highly
unlikely that the monopine will fail structurally in a wind event where the design wind speed is
exceeded within the range of the built-in safety factors.
Should the wind speed increase beyond the capacity of the built-in safety factors, to the point of
failure of one or more structural elements, the most likely location of the failure would be within the
monopine shaft. Assuming that the wind pressure profile is similar to that used to design the
monopine, the monopine will buckle at the location of the highest combined stress ratio within the
monopine shaft. This is likely to result in the portion of the monopine above “folding over” toward the
portion below. Please note that this letter only applies to the above referenced monopine
designed and manufactured by Sabre Towers & Poles. In the unlikely event of total separation,
this would result in the portion above collapsing within a radius of 80 feet.
Sincerely,
Keith J. Tindall, P.E.
Vice President of Engineering