Section 15.0 - Existing Structures

ID #1052

Section 15.4 question regarding existing tower re-analysis; submitted 12/31/2007

QUESTION: I was looking for clarification as to whether or not it is a requirement of TIA-222-G to complete a structural analysis on a tower when antennas and lines are being removed. I have had conflicting answers from those who are working with the standard daily and would like to hear from TIA on the matter. RESPONSE: The intent of the Standard was to require a structural analysis when the number of appurtenances increases or decreases. This was required to cover the "obvious" situations where increasing the number of appurtenances would increase member forces but also to cover the "not so obvious" situations where removing appurtenances could result in increased member forces. This situation could occur for guyed masts and for tapered self-supporting latticed towers supporting significant straight sections. The intent was not to override the judgment of a qualified engineer who may decide that a full structural analysis would not be required for a specific situation. This is similar to when the type of antenna is changed. The engineer may decide that although the type has changed, the change in loading on the structure would be of no significance. Response 12/31/2007 Response amended on 11-1-2012 Per Addendum 2 Evaluation of appurtenance changes for existing Class I and II structures originally designed in accordance with a previous revision of this Standard may be based on Revision F of this Standard. The appurtenance change shall be considered significant when strength requirements increase by more than 5% for any structural component, in which case the required modifications and/or final acceptance shall be determined in accordance with this Standard. 121

Tags: 15.4

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Last update: 2012-11-01 20:06
Author: Brian Reese
Revision: 1.1

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