Section 13.0 - Plans, Assembly Tolerances and Marking

ID #1091

Section 13.3 question regarding plumb measurement of monopoles; submitted 7/20/2011

QUESTION: My question involves the plumb measurements of monopoles obtained through our regular tower inspections. It is often difficult to obtain accurate field measurements of monopoles due to well known issues such as existing loading, wind, solar expansion as well as the difficult task of transit set-ups to read these measurements accurately (and in the right directions). Since the pole is a single element - it is up to the inspectors discretion in which directions the transits should be placed (at daybreak) to read the "worst" deflection. 1. If we measure only the maximum deflection at the top of a monopole - will that be sufficient to address the out-of-plumb issue using a P-delta analysis to prove the structure is compliant? If the P-delta analysis is found passing that should indicate the pole in its deflected condition is capable of supporting its existing loading and should be considered as compliant, correct? RESPONSE: Measurement(s) of the out of plumb condition must be sufficient to accurately reflect the installed condition. The number of measurements is dependent upon the installed condition and the engineer of record's review of the significance of the measured values. Treatment of the measurements utilizing the standard addendum 1 Annex J.1 (K) Note is the acceptable means of resolving conditions that are not in conformance with Section 13. It is as follows: Note: The assembly tolerances specified in Section 13.0 represent tolerances that are readily obtainable using ordinary installation methods as opposed to tolerances beyond which structural capacity is reduced to insignificance. Measured mis-alignments within the tolerances specified in Section 13.0 may be ignored in the analysis of a structure; however, when measured mis-alignments exceed the specified tolerances, the measured mis-alignments must be accounted for in the analysis model of that structure. Response 7/20/2011

Tags: 13.3

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Last update: 2013-09-27 22:41
Author: Brian Reese
Revision: 1.0

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