Handbook of Civil Engineering Calculations

3. Determine the design flexural strength
   To determine <feMn* (me design flexural strength), refer to the Load Factor Design Selec-
   tion Table for Beams in the AISC LRFD Manual. Since the W14 x 159 is not tabulated
   therein, the basic equations are used instead.
   M 1 / M 1 \2
   Q = 1.75 + 1.05 —
   l

• 0.3 —M < 2.3
  M 2 \M 2 I

Again, M 1 IM 2 = -1.0.

Cb = 1.75 + 1.05(-1.0) + 0.3(-1.0)

2

= 1.0

If C 6 = 1.0, Mn = Mp ZxFy for bending about the jc axis if Lb < L 77 ; Z^ = &QQry/Fy) for W

shapes bent about the x axis [Eq. (F 1-4)}. For a W14 x 159, ry = 4.0 in (10.2 cm) and

(300 x 4.0 in)/(12 in/ft)

£,= ^ 16.7 ft (5.1 m)

Because (Lb = 15.0 ft) < (Lp = 16.7 ft),

M.-ZS,-

287in3

,^l

kiPS/in2

-8611dp.ft(1167kNm)

and <M4r = 0.90 x 861 kip-ft = 775 kip-ft (1050 kNm)

Substituting the interaction formula, we obtain

8 210 kip-ft

0.65 + — x £—

9 775 kip-ft

= 0.63 + 0.24 = 0.87 < 1.0 o.k.

By a similar solution of interaction formula (Hl-Id) 9 it can be shown that a W14 x 145 is

also adequate.

Related Calculations. This procedure is the work of Abraham J. Rokach, MSCE,

Associate Director of Education, American Institute of Steel Construction. SI values were

prepared by the handbook editor.

SELECTION OF CONCRETE-FILLED

STEEL COLUMN

Select a 6-in (15.2-cm) concrete-filled steel-pipe column for a required axial compressive
strength of 200 kips (889.6 kN), where KL = 10.0 ft (3.05 m), Fy = 36 ksi (248 MPa),
fcf = 3.5 ksi (24.1 MPa), using normal-weight concrete = 145 Ib/cu ft (2320 kg/cu m)

Calculation Procedure:

1. Try a standard-weight concrete-filled pipe


2. Analyze the selected column