Select a W section to serve as purlins between roof trusses spaced at 4.6 m on centers. Assume all loads passes through the Centroid of the purlins. Spacing of purlins is 1.4 m on centers. Assume that the purlins are fully laterally supported and subject to the following: Loads Snow = 1440 N/m2 of roof surface Roofing = 288 N/m2 of roof surface Wind surface = 720 N/m2 perpendicular to roof surface Slope of the roof truss is 1 vertical to 2 horizontal. Sag rods are provided at the midpoints of the truss. A36 steel, Fy=248 MPa Select from any W section listed in the table below. Use ASD
Select a W section to serve as purlins between roof trusses spaced at 4.6 m on centers. Assume all loads passes through the Centroid of the purlins. Spacing of purlins is 1.4 m on centers. Assume that the purlins are fully laterally supported and subject to the following: Loads Snow = 1440 N/m2 of roof surface Roofing = 288 N/m2 of roof surface Wind surface = 720 N/m2 perpendicular to roof surface Slope of the roof truss is 1 vertical to 2 horizontal. Sag rods are provided at the midpoints of the truss. A36 steel, Fy=248 MPa Select from any W section listed in the table below. Use ASD
Chapter2: Loads On Structures
Section: Chapter Questions
Problem 1P
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Question
Transcribed Image Text:For ASD.
Mas
May
Mnx/2b Mny/92b
Max
M
ay
=
=
M
ax +
M
nx
Ω
+
w, L²
8
w, L²
32
= 8.68kN m
= 0.753kN m
M
M
ay
≤1.0
ny
Ω
≤1.0
Wx= 3282-28 N/m
Wy= 1138.87 W/m
No LTB: M₁ = Mp
Mpx = Fy(Zx) = 248×93.9(10³) = 23.29kN.m
For Cb: Cb = 1.30
M=1.30(23.29) = 30.277kN.m
Mpy = Fy(Zy) = 248x 25.6(10³) = 6.35kN-m
8.68
30.277
1.67
+
0.753
6.35
1.67
= 0.677 < 1.0
check if section is compact
b₁
100.026
2t₁
2(4.928)
=
= 10.15
8
.. section is adequate
Use W6x8.5
< 0.38
E
Check the upper limit:
Z₁
= 1.55 < 1.6 ..My = Mpy = 6.35kN m
S₁
= 10.79
Fy
.. section is compact
Transcribed Image Text:Select a W section to serve as purlins between roof trusses spaced at 4.6 m on centers. Assume all loads passes through the
Centroid of the purlins. Spacing of purlins is 1.4 m on centers. Assume that the purlins are fully laterally supported and
subject to the following:
Loads
Snow = 1440 N/m2 of roof surface
Roofing = 288 N/m2 of roof surface
Wind surface = 720 N/m2 perpendicular to roof surface
Slope of the roof truss is 1 vertical to 2 horizontal.
Sag rods are provided at the midpoints of the truss. A36 steel, Fy=248 MPa
Select from any W section listed in the table below. Use ASD
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