Determine structural member sizes.
B-11
(1) Braced Frames (Low Roof).
Determine Design Loads:
Per paragraph 7-3.a (5) (a), structural steel braced frames will conform to the requirements of the AISC
seismic provisions for structural steel buildings.
Axial load per braced frame;
1-ft = 0.30m
2.5k / 2
Phoriz
= 0.78k (3.47KN)
Pu = Paxial
=
=
Therefore;
2 cosφ 2(0.8)
Two brace elements per brace frame
Design Members (use HSS w/ Fy = 46ksi or 317.2MPa):
Per paragraph 7-3.b (3), the effective out-of-plane unbraced length is equal to two thirds of the total length.
Therefore;
KL = (2/3)25'= 16.7'or 200" (5.09m)
KL 1000
h
110
≤
≤λp =
Per AISC seismic provisions;
r
t
Fy
Fy
KL Fy
200" 46ksi
r≥
=
= 1.36 - in (34.5mm)
Therefore;
1000
1000
110
λp =
= 16.2
ksi
46
Try TS 4X4X1/4;
From AISC column load tables for an effective length KL = 17' φc Pn = 42 k > 0.78k = Pu
O.K.
φt Pn = 0.9(46ksi )3.59 - in2 = 149 k > 0.86k (662.8KN > 3.83KN)
O.K.
O.K.
r = 1.51" > 1.36" = rreq'd
h/t = 16 < 16.2 = λp
O.K.
Choose TS 4X4X1/4 (TS101.6mmX101.6mmX6.35mm)
H4-21
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