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AISC Manual Table 3-2: W12×26 beam, F_y = 50 ksi, unbraced length 10 ft

ToolLateral-Torsional Buckling
SourceAmerican Institute of Steel Construction (2017). Steel Construction Manual, 15th ed. AISC, Chicago. Table 3-2 (W12×26, F_y = 50 ksi) and ANSI/AISC 360-16 Section F2.
LevelProfessional

Problem

A W12×26 beam of ASTM A992 steel (F_y = 50 ksi) is bent about its strong axis with an unbraced length of 10 ft and uniform moment (C_b = 1.0). Find the limiting lengths L_p and L_r of AISC 360 Section F2 and the nominal flexural strength M_n at that unbraced length.

Inputs to Enter

  • Section from properties: A 7.65 in², I_x 204 in⁴, I_y 17.3 in⁴, S_x 33.4 in³, Z_x 37.2 in³, J 0.30 in⁴, C_w 607 in⁶, h_0 11.8 in (AISC Table 1-1); or plates b_f 6.49, t_f 0.38, d 12.2, t_w 0.23 in
  • E = 29,000 ksi, G = 11,200 ksi, F_y = 50 ksi
  • L_b = 120 in, C_b = 1.0 (entered), applied M_a = 1,000,000 lb-in, FS 1.0
Open the Lateral-Torsional Buckling tool (loaded with this example)

Answers

  • L_p = 63.74 in (Table 3-2: 5.31 ft = 63.7 in)
  • L_r = 178.8 in (Table 3-2: 14.9 ft = 178.8 in)
  • M_n = 1,522,000 lb-in at L_b = 120 in (inelastic range, tool value)
  • C_w from the plate outline 603 in⁶ against the tabulated 607 in⁶ (thin-walled 605)

Notes

The tool's default inputs are this beam; press Submit. The AISC lengths are read from Table 3-2 to three figures, the tool keeps all digits of the F2 equations.