SPECIFICATION FOR THE DESIGN OF - Transcon Steel

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.
• Steel 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’.