Florida's tower design requirements will change March 15, 2012

Discussion in 'Design, Development and Standards Discussions' started by Wireless Estimator, Feb 17, 2012.

  1. Wireless Estimator

    Wireless Estimator Administrator Staff Member

    If you're getting ready to permit a structure in Florida, it's important to note that the 2010 Florida Building Code will go into effect March 15, 2012 and the changes will require engineers to take into account that they must convert an Ultimate Design Wind Speed to a Nominal Design Wind Speed per Section 1609.3.1.

    Although Section 1609.1.1, Exception 5 allows the use of TIA-222-G, the wind speed and structure class are different.

    Wind speed maps have all been altered and the Ultimate Design Wind Speed is to be used. However, a local jurisdiction’s requirements may surpass the specified Ultimate Design Wind speeds.

    These will be higher than the previous 3-second gust wind speeds and it will be necessary to take the Ultimate Design Wind Speed and convert it to 3-second wind speeds per the table (1609.3.1) in the 2010 FBC.

    If a new county map is not available - only Orange County has one to date - engineers will be required to use the overall Florida map (2010 FBC Figure 1609A). The wind speeds of Figure 1609A in the 2010 FBC are taken from ASCE 10-7.

    Structures near shorelines in hurricane prone regions are no longer exempt from being classified as Exposure Category D.

    Exposure Category D applies to terrain that is flat, unobstructed shorelines exposed to wind flowing over open water for a distance of 5000 ft.

    Category D includes smooth mud flats, salt flats and other similar terrain. It extends inland a distance of 600 feet or 20 times the height of the structure.

    In lieu of Importance Factors, the 2010 FBC uses Risk Categories.

    The Ultimate Design Wind speed for communication towers and steel antenna supporting structures not designated as providing essential services shall be considered as Risk Category II.

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