SPECIFICATION FOR THE DESIGN OF - Transcon Steel

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32 Commentary on the Prescriptive Method for One and Two Family Dwellings - 2004 • Deflection Criteria: L/240 for C&C ASCE 7 wind loads with 0.7 factor • Other Assumptions: • Studs are simply supported beams. • Maximum roof overhang of 24” on either side of roof. • Roof slopes limited to a range of 3:12 to 12:12. • Ceilings, roofs, and floors span full width of the house; no interior load bearing walls. Headers • Headers Supporting: Roof and ceiling and one floor, roof and ceiling, roof and ceiling with center beam supporting first floor • Header Types: Back-to-Back, Box Beam and L-Header • Header Size Range: 350S162-33 through 1200S162-97 • L-Header Size Range: 600L150-43 through 1000L150-68 • Ground Snow Loads: 20 psf, 30 psf, 50 psf, and 70 psf • Attic Live Load: No attic live load is considered in the header design. Tables are footnoted to allow for attics with storage by jumping to the next snow load column. • Snow Load: 0.7xGround Snow Load (16 psf minimum) • 2 nd Floor Dead Load: 30 psf • 2 nd Floor Live Load: 10 psf • 2 nd Floor Wall Dead Load: 10 psf (for 8 feet) • Roof Dead Load: 7 psf • Ceiling dead Load: 5 psf • Yield Strength: 33 ksi steel • Design Checks: All headers designed per AISI Standard for Cold-Formed <strong>Steel</strong> Framing – Header Design (AISI, 2001c). • Deflection Criteria: L/240 for total load • Other Assumptions: • Headers are simply supported beams. • Maximum roof overhang of 24”. • Roof slopes limited to a range of 3:12 to 12:12. • Ceilings, roofs, and floors span the full width of the house, no interior load bearing walls, except as noted. • The allowable capacity of each header is calculated as twice the allowable capacity of a single member (i.e. no composite action). • The number of king and jack studs was determined by taking the width of the opening and dividing it by the stud spacing. The results were then rounded up to the next full stud. Ceiling Joists • Joist Spacing: 16” and 24” • Live Loads: 10 psf and 20 psf • Spans: Single and two-equal spans, with and without web stiffeners (uniform load over the entire two-spans; no alternate loading was considered) • Joist Size Range: 350S162 through 1200S162, 33 to 97 mil thickness
Commentary on the Prescriptive Method for One and Two Family Dwellings - 2004 33 • Ceiling Dead Load: • Yield Strength: • Bracing: • Deflection Criteria: • Basic Load Combinations: • Design Checks: • Bearing Width: 5 psf 33 ksi steel Unbraced, mid-span, and third point bracing L/240 for total load LRFD loads and load combinations Bending, shear, combined bending and shear, combined bending and web crippling 3-1/2” at ends and at interior supports Rafters • Rafter Spacing: 16” and 24” • Ground Snow Loads: 20 psf, 30 psf, 50 psf, and 70 psf • Wind Speeds: Same as wall studs wind speeds • Seismic Design Categories: A, B, and C • Spans: Single and two-equal spans • Joist Size Range: 550S162-33 through 1200S162-97 • Roof Dead Load: 12 psf • Yield Strength: 33 ksi steel • Roof Pitch: 3:12 to 12:12 • Deflection Criteria: L/240 for live load and L/180 for total load • Snow Load = 0.7 x ground snow load (16 psf minimum) • Basic Load Combinations: LRFD loads and load combinations • Bracing: Mid-span bracing • Other Assumptions: • Rafter spans are designed based primarily on gravity loads; hence the rafter spans are reported on the horizontal projection of the rafter, regardless of the slope. The gravity loads consist of a roof dead load and the greater of a minimum 16-psf live load or the applied roof snow load. • Wind load effects are correlated to equivalent snow loads. Wind pressures were calculated using the ASCE 7-98 Components and Cladding pressure coefficients. Wind loads acting perpendicular to the plane of the rafter were adjusted to represent loads acting orthogonal to the horizontal projection of the rafter. Wind loads were examined for both uplift and downward loads and the worst case was correlated to a corresponding snow load. • The roof system must consist of both ceiling joists (i.e. acting as rafter ties) and rafters. • Rafters are simply supported beams. Summarized in Table A5.2 are the loads and other design assumptions used in developing the Prescriptive Method.
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SPECIFICATION FOR THE DESIGN OF - Transcon Steel

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