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 cos*φ * 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

≤

≤*λ*p =

Per AISC seismic provisions;

r

t

Fy

Fy

KL Fy

200" 46ksi

r≥

=

= 1.36 - in (34.5mm)

Therefore;

1000

1000

110

= 16.2

ksi

46

Try TS 4X4X1/4;

From AISC column load tables for an effective length KL = 17' *φ*c Pn = 42 k > 0.78k = Pu

r = 1.51" > 1.36" = rreq'd

h/t = 16 < 16.2 = *λ*p

H4-21

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