Section 2.0 - Loads

ID #1104

2.6.7.4 Gust Effect Factor for Structures Mounted on Other Structures

Question: I would like an interpretation as to what Gh should be used for attaching antenna mounts to existing building walls and for figuring ballast for roof top antenna mounts. I've been using 1.35 and then paying the price when evaluating the ballast impact on the roof structure. The first paragraph talks about mounting to flexible structures. The second paragraph talks about using the Gh for the parent structure. Most buildings we encounter have height width rations of much less than 5. Response: In accordance with TIA-222-G Section 2.6.9 a gust factor of 1.0 and a directionality factor per Table 2-2 shall be used for roof mounted appurtenances. The TIA standard does not specifically address wind speed up for appurtenances mounted on roof top structures; however, ASCE 7 provides guidance to address this issue. Section 2.6.7.4 was not intended for antenna mounts on roof tops.

Tags: 2.6.7.4, 2.6.9

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Last update: 2012-06-07 22:39
Author: Robert Hamlin
Revision: 1.0

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