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a • <br /> Ms. Finsch <br /> Tiscareno Associates <br /> Plan Check Number: B1801-032, First Review <br /> March 13, 2018 <br /> Lateral System: <br /> 34.The wind loads on the main wind force resisting system (MWFRS) are provided on structural <br /> calculations pages SC241 through SC245. See IBC Section 1609.1.1. The following comments <br /> should be addressed: <br /> a. The leeward wind pressures on pages SC243 and SC245 have been calculated using <br /> varying Krvalues per ASCE 7-10 Table 27.3-1. Leeward pressures shall be based on a <br /> single Kh value corresponding to the maximum height of the structure per Figure 27.4-1. <br /> The design pressures should be revised. <br /> b. The load on the MWFRS does not appear to include the contribution of loads on the <br /> parapets and walls at Level 4 and the roof. Additional loads shall be included per ASCE 7- <br /> 10 Section 27.4.5 and Figure 27.6-2. A load contribution shall be included for each parapet <br /> and wall normal to the wind direction, including rooftop walls interior to the building <br /> perimeter. <br /> c. The base shears on pages SC243 and SC245 are 747 kip and 164 kip, respectively. The <br /> ASD force levels are 448 kips and 98 kip, which exceed the values of 381 and 84 shown on <br /> page SC247. The wind loads should be revised. <br /> d. Page SC247 states that the seismic load controls. However, wind shear at the top story for <br /> the east-west direction exceeds the seismic shear and should control the design. <br /> 35. A lateral analysis of the structure for wind loading should be performed based on the following <br /> comments: <br /> a. Distribution of the wind loading shall be determined considering the diaphragms as rigid or <br /> semi-rigid in both directions. See IBC Section 2306.1 and AWC SDPWS-15 Section 4.2.5.2 <br /> Item 3. Shear wall designs shall consider wind loading where they exceed the seismic <br /> shear loads. The entire structure must be considered in the analysis, including the wing in <br /> each direction that may otherwise be idealized as flexible. <br /> b. The use of a rigid or semi-rigid diaphragm shall be substantiated per AWC SDPWS-15 <br /> Section 4.2.5. Alternatively, semi-rigid diaphragms may be used without analysis. <br /> c. The relative stiffness of the walls shall be considered per IBC Section 1604.4 and AWC <br /> SDPWS-15 Section 4.2.5.2. Where walls are not oriented parallel to the direction of <br /> loading, they shall be modeled explicitly with their true orientation, or an effective stiffness <br /> vector shall be used for each direction. <br /> d. The wind analysis shall consider the load combinations of ASCE 7-10 Section 27.4.6 and <br /> Figure 27.4-8. All cases shall be considered unless documentation substantiates that <br /> structure satisfies the requirements of Section D1.2.1 at each level. See IBC Section <br /> 1609.1.1. <br /> 36.The wind loading applies to the exterior wall planes instead of a distributed load throughout <br /> the diaphragm. Collectors shall be provided to distribute lateral loads to shear walls at the <br /> interior of the diaphragm. See IBC Section 1604.4 and 2306.1, and AWC SDPWS-15 Sections <br /> 4.1.1 and 4.1.4. <br /> 37.The roof diaphragm on Sheet S201a-SS has a cantilever length of at least 36 feet between <br /> Grids S-2/S:10. APA SDPWS-15 Section 4.2.5.2 Item 4 limits the length to 35 feet. The length <br /> should be reduced by moving the diaphragm edge or adding another row of shear walls. Note <br /> that adding shear walls is expected to result in a Type 4 Horizontal Structural Irregularity per <br /> ge8of11 <br /> CITY OF EVERETT • 3200 Cedar Street • Everett, WA 98201 • (425) 257-8810 • Fax(425) 257-8857 <br />