3000 ROCKEFELLER AVE ADMIN BLDG WEST 2022-05-13

4 R Page 2 0 PROJECT: SNOHOMISH COUNTY HVAC IMPROVEMENT, ADMINISTRATION EAST BUILDING EVERETT, WA BASIS OF DESIGN The scope of this structural design packet is limited to: 1. The seismic anchorage for replacement and new rooftop mechanical equipment. 2. Design of supplemental steel framing to support the proposed mechanical equipment. 3. Confirmation of the existing framing and load path for the revised loads. The existing roof framing consists of composite slab with 5-1/2" normal weight concrete on W3 x 20 ga metal deck. The roof framing consists of WF composite beams that span east -west with approximately 10' tributary width between beams. The loads maps from the original structural drawings indicate that the bay was originally designed for 125 psf non -reduced live load. The incoming loads are less than the original design live load Currently, the existing cooling towers are spring -isolated and bear on 1'-6" by 1'-6" concrete curbs that we installed during a previous mechanical upgrade. The replacement cooling towers and fluid cooler will be supported by the existing concrete curb. Supplemental steel will be configured to span between concrete curbs to support incoming CT and fluid cooler. New spring isolators will be configured. A welded, wide -flange base rail will be installed between the equipment and the spring -isolators. Smaller mechanical equipment will be supported by factory curbs. 0 Design Approach: • Use MCK seismic spreadsheet to determine controlling wind/seismic reactions. o Seismic will control as mech equipment is located within an existing screen wall. • Design WF base -rail with deflection critera per incoming mechanical equipment. • Select spring -isolator. • Design supplemental steel and embed plates. o Configure HSS as steel will be loaded in -plane and out -of -plane loads. o Detail epoxy connections for embed plate connections. • Confirm support framing (composite beam) for revised loads. • Design screw connection fastening adapter curb to existing curb. Overturning moment and base shear will be calculated for the connection of the replacement units per criteria defined in ASCE 7-10, Chapter 13. REFERENCES • IBC 2015 with WA Amendments • Minimum Design Loads for Buildings and Other Structures, ASCE Standard-SEI/ASCE 7-10 • MKA Structural Drawings: S001-S606, Issued for construction, rev 1, dated: 10-17-03. LOADING CRITERIA Dead Loads = Self Weight of replacement mechanical equipment + self wt of steel and springs. 0 5005 3rd Avenue South ■ Seattle, WA 98134 ■ 206.762.3311 ■ FAX 206.762.2624 Colorado ■ California ■ Idaho ■Kansas ■ Minnesota ■ Montana ■ Oregon ■ Texas ■Washington ■ Wisconsin