General Dynamics 500-0646, Operation Manual

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500-0646A D-1
APPENDIX D. MOUNTING CONSIDERATIONS
There are two basic mounting approaches for small antennas: ground mount and roof
mount. For ground mounting, the user should build a qualified antenna foundation and
consult a structural professional for the foundation soil structures. For roof mounting,
some special considerations should be taken as follows:
The antenna system should be properly supported to provide transfer of all the antenna
loads into the main building structures, sustaining all the wind loading exerted on the
antenna along with the antenna self-weight. The designed roof-mounting frame must
distribute loads from the antenna interface location to the building’s roof beams and
columns.
The structural concepts that will be incorporated to achieve an effective frame
configuration are as follows:
•
At each foundation interface location, provide a direct load path for each load vector
component.
•
Where feasible, align axes of framing members to the vector direction of the applied
loads. This can reduce bi-axial bending and torsional effects.
•
Eccentricity between the applied load vector and the framing member centroid can
produce large torsional forces. These torsional effects require more complex joint
details to transfer forces properly and introduce increased structural deflection.
•
Reinforcing members are required where the antenna structure is bolted to a beam.
The reinforcement should be designed to prevent flange bending and web crippling
under concentrated load.
•
Use correct anchors in concrete surface.
•
Avoid use of double-nutting (one nut on top and one nut on bottom of the plate) to
provide leveling. This will induce undesirable anchor bolt bending conditions.
•
Use friction type connections where it is possible to provide 100% load reversal
capacity.