Laserfiche WebLink
NWTE NorthWest Tower Engineering <br /> 76th Street, Everett, WA Report No. 210622.08 February 1, 2021 <br /> Exposure Category B (wooded or suburban area) and Topographic Category 1 (flat or rolling <br /> terrain, no wind speed-up) were used for the analysis. <br /> Analysis Method <br /> A three-dimensional finite element model of the tower was created using tnxTower Version <br /> 8.0.7.5 (Tower Numerics Inc., 2020). This computer software program calculates and distributes <br /> wind and ice loads in the model. It calculates the resulting forces (required strength) in all <br /> structural members and determines tower deflections and foundation loads. Required strength <br /> of each structural member is compared to each member's design strength determined using the <br /> TIA-222-G standard. <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 /> Leg 26 27 <br /> 180 — 0 Diagonal 34 33 <br /> Horizontal 1 1 <br /> The attached tables contain more detailed lists of member forces and capacities. Capacities of <br /> all structural members were found to be adequate. <br /> Calculations confirmed the adequacy of the anchor bolts and the bolts in each leg splice and <br /> bracing connection. Welds, plates, and other elements of the connections are assumed to be <br /> adequate. <br /> A foundation drawing was not provided. However, foundation reactions listed on the Valmont <br /> Microflect drawings were increased by a factor of 1.35 per TIA-222-G, Section 15.5, to allow a <br /> comparison to be made with the calculated foundation reactions from this analysis. The factored <br /> original design reactions were found to be significantly greater than the calculated reactions <br /> from this analysis. Based on this comparison, the foundation is considered to be adequate. <br /> Seismic calculations were performed using the equivalent lateral force procedure in accordance <br /> with ASCE 7-10, Minimum Design Loads for Buildings and Other Structures. Seismic forces <br /> were distributed over the height of the tower in accordance with ASCE 7-10. Resulting values <br /> for shear forces in the tower were then calculated at multiple levels and compared with shear <br /> forces generated from wind loads. Wind load was found to govern over the full height of the <br /> structure. <br /> NorthWest Tower Engineering 4 www.nwtower.net <br /> 3426 Broadway,Suite 302,Everett,WA 98201 Tel 425-258-4248 Fax 425-258-4289 <br />