SPECIFICATION FOR THE DESIGN OF - Transcon Steel

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30 Commentary on the Prescriptive Method for One and Two Family Dwellings - 2004 A4 Deflection Limits Table A4.1 Deflection Limits Framing Component Deflection Due to Deflection Due to Live Load 1 Total Load 1 Floor Joists L/480 L/240 Headers L/360 L/240 Wall Studs 2 L/240 - Ceiling Joists L/360 L/240 Roof Rafters L/240 L/180 1 Unfactored loads were used to calculate deflections. 2 A factor of 0.7 was applied to the deflection limit of load combinations including components and cladding wind loads in accordance with the IRC (ICC, 2000b). A5 Design Checks and Assumptions Summarized in Table A5.1 are the design checks for each framing component. Framing Component Bending Shear Table A5.1 Design Checks Web Crippling Bending & Shear Bending & Web Crippling Axial Axial & Bending Deflection Floor Joists 1,2 √ √ √ √ Headers 3 √ √ 4 √ 4 √ √ Wall Studs √ √ √ √ √ √ Ceiling Joists √ √ √ √ √ 5 √ Roof Rafters √ √ √ 1 All joists should have web stiffeners at support locations. 2 Combined bending and shear was checked for double spans. 3 The header connection to the stud via a clip angle was considered a web stiffener. 4 Shear, and combined bending and shear, do not need not be checked (AISI, 2001c). 5 For two (continuous) ceiling joist spans without web stiffener. General Assumptions • All members are assumed to have 2-1/2” x 4” (1-1/2” x 4” for studs) web holes along the centerline of the web. Holes are not less than 24 inches on center, and are not within 10 inches from the end of the member or bearing condition. • <strong>Steel</strong> comes in 33 and 50 ksi yield strength. • ASCE 7 (ASCE, 1998) wind load provisions are used. • Design limited to Seismic Design Category A, B, C, D1, D2 and E, in accordance with the IBC (ICC, 2000a). • LRFD load combinations are used. • Increase in yield strength due to cold work of forming is used where allowed. • Design thickness is minimum thickness/0.95. • House widths of 24’, 28’, 32’, 36’ and 40’.
Commentary on the Prescriptive Method for One and Two Family Dwellings - 2004 31 Floor Joists • Joist Spacing: 12”, 16”, 19.2” and 24” oc • Live Loads: 30 psf and 40 psf • Span: Single (simply-supported span) and Two-equal spans with stiffeners at bearing locations (uniform load over the entire two-spans; i.e., no alternate loading is considered) • Joist Size Range: 550S162-33 to 1200S162-97 • Yield Strengths: 33 ksi steel for single spans and 33 and 50 ksi steel for multiple spans • Floor Dead Load 10 psf • Design Checks: Bending, shear, and combined shear and bending (for two-spans only) • Deflection Criteria: L/480 for live loads and L/240 for total loads • Bracing: Joists considered to be continuously braced at the top flange by floor sheathing • Bearing Stiffeners: All floor joists are assumed to have stiffeners at bearing support locations • Bearing Length: Minimum bearing length of 1½” at end supports and 3½” at interior supports Structural Wall Studs • Stud Spacing: 16” and 24” on center • Wind Speed: 85 through 130 mph Exposures A/B (3-sec. gust wind speeds) with adjustments for Exposure C (enclosed buildings) • Seismic Design Category: A, B, C, D1, D2 and E • Stud Heights: 8’, 9’, and 10’ • Stud Size Range: 350S162 and 550S162-33 to 97 mil thickness • Ground Snow Loads: 20 psf, 30 psf, 50 psf, and 70 psf • Attic Live Load: No attic live load acting on the studs. Tables are footnoted to allow attics with storage by jumping to the next snow load column • Snow Load: 0.7xGround Snow Load (16 psf minimum) • Stud Bracing: Bracing of the interior and exterior flanges of the studs by sheathing or mechanical bracing (mechanical bracing at mid-height for 8' studs, 1/3 point for 9' and 10' studs) • Yield Strengths: 33 and 50 ksi steel • 2 nd Floor Dead Load: 10 psf • 2 nd Floor Live Load: 30 psf • 2 nd Floor Wall Dead Load: 10 psf • Roof Dead Load: 7 psf • Ceiling Dead Load: 5 psf • Design Checks: Bending only: C&C loads per ASCE 7 (ASCE, 1998) Combined axial and bending: MWFRS loads and load combinations
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SPECIFICATION FOR THE DESIGN OF - Transcon Steel

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