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Structural Analysis Guidelines for Antennas:
The below listed standards and methods are used to calculate the Survival Wind
Velocity and all other related moments, stresses and deflections:
TIA Document
Telecommunications Industry Assoc., Minimum Standards for Communications
Antennas, Base Station Antennas.
TIA-329-C (August 2003)
Definitions of Wind Velocity and Loading:
Rated Wind Velocity-
The Rated Wind Velocity and Loading for antennas is calculated using industry
standard TIA-329-C. The calculation for rated wind velocity determines the
maximum wind velocity at which the mechanical stresses in the antenna are below
the yield point of the materials by a safety factor of not less than 1.65 as
specified in 5.1.2 of the standard.
Rated Wind Velocity calculated using this methodology is the wind speed at which
an antenna can endure sustained exposure without failure.
Survival Wind Velocity-
The calculation for Survival Wind Velocity determines the maximum wind velocity
at which the mechanical stresses in the antenna components are just below the
allowable yield strength of the mast, boom and dipole material. Survival Wind
Velocity calculated using this method is the wind speed at which an antenna
cannot endure sustained exposure over longer periods of time without
experiencing some degree of material deformation or malfunction. Inspection
after the survival wind speeds is recommended.
Flat Plate Equivalent and Horizontal Thrust Calculation.
Notes on how to calculate flat plate equivalent areas and horizontal wind thrust
for antennas specified in Sinclair published catalogues. FPE is defined as the
flat plate area that would result in the same wind load as the antenna under the
same wind condition. To determine the flat plate equivalent area is to multiply
the drag coefficient by two thirds of the projected area of a structural member.
1) The Flat Plate Equivalent Area, ft²:
FPE= Cd 2/3 A, published value.
Where: FPE, is the Flat Plate equivalent Area, ft²
2/3, conversion factor for flat surfaces areas.
A, is the projected area
Cd, is the drag coefficient
The standard values for drag coefficients, CSA-37-94:
For round members Cd=1.0
For flat plates Cd=1.5
Note: The drag coefficient is difficult to determine, it varies with the shape,
aspect ratio and surface roughness of the antenna or its structural members.
Published text book or data from standard associations i.e. CSA-37, TIA/EIA may
be used for this calculation, however the most reliable drag coefficients are
experimentally determined by wind tunnel trails. For the selection of the drag
coefficient Sinclair makes use of both sources.
2) Calculation of Horizontal Thrust or Wind Load (W):
The horizontal thrust or wind loading is the product of the flat plate
equivalent area (FPE) and the wind velocity pressure (P) which is expressed in
pound force, Lbf.
Calculating the Wind Load acting on Antennas:
W= P (FPE), in Lbf.
Where: P, is the wind velocity pressure in pounds per square foot, lb/ft²
FPE, is the Flat Plate Equivalent Area, ft² (see paragraph 1)
Calculating the wind velocity pressure, TIA-329C:
P=KV2, in lb/ft²
Where: K, is the wind conversion factor, a nominal value of K for pressure on
the projected areas of flat surfaces is 0.0042.
V, is the stated maximum wind velocity in miles per hour, mph.
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