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NWTE NorthWest Tower Engineering <br /> WSDOT Monopole, Everett, WA Report No. 140636.05 September 16, 2014 <br /> Wind Load Specifications <br /> A rigorous structural analysis was performed using the provisions of the current design <br /> standard, TIA-222-G, "Structural Standard for Antenna Supporting Structures and Antennas." <br /> This standard is referenced in the 2012 International Building Code (IBC). The minimum basic <br /> wind speed of 85 mph (Vasd, 3-second gust) as listed in the standard for Snohomish County was <br /> used. A basic wind speed of 30 mph in combination with a design ice thickness of IA" as listed in <br /> the standard was also considered. Exposure Category B (suburban or wooded area), <br /> Topographic Category 1 (flat or rolling hills) and Structure Class III (essential facility) were used <br /> for the analysis. <br /> Wind loads calculated using a basic wind speed of 85 mph (Vasd) with a wind load factor of 1.6 <br /> and importance factor of 1.15 for Class III structures per the TIA-222-G standard are similar to <br /> those calculated using an ultimate design wind speed of 115 mph (V„It) for Risk Category IV <br /> with wind load and importance factors of 1.0 per the 2012 IBC and ASCE 7-10 standard. <br /> Analysis Method <br /> A three-dimensional finite element model of the tower was created using RISA Tower Version <br /> 5.4.2.0 (RISA Technologies 2010). This computer software program calculates and distributes <br /> wind and ice loads in the model. It calculates the resulting stresses in all structural members <br /> and guy wires, and determines tower deflections and foundation loads. Calculated member <br /> stresses were compared to allowable values set forth in the design standard. <br /> WSDOT requires that stress levels in all structural members be kept below 90%. <br /> Analysis Results <br /> The following ratios of required strength to design strength for the tower's structural members <br /> were found: <br /> MEMBER STRENGTH RATIO <br /> Elevation Existing Configuration Proposed Configuration <br /> Member <br /> (ft) Maximum % Capacity Maximum % Capacity <br /> Monopole Shaft 42 43 <br /> 150 - 0 Base Plate 13 I 14 1 <br /> Anchor Rods 35 36 <br /> The attached tables contain more detailed lists of member stresses. For both appurtenance <br /> configurations, strength ratios are below the WSDOT required maximum 90%. <br /> Seismic calculations were performed using the equivalent modal analysis procedure as set forth <br /> in Section 2.7 of the TIA-222-G standard. Seismic forces on each pole shaft section were <br /> calculated. The total seismic shear is much less than the total wind load and when distributed as <br /> specified over the full tower height does not produce overstress in any of the tower's structural <br /> members. <br /> NorthWest Tower Engineering www.nwtower.net <br /> 2210 I iewitt Ave,Suite 209,Everett,WA 98201-3767 ` �) rel 425-258-4248 Fax 425-258-4289 <br />