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SYMBOLSSteel Columns subject to axial force and flexure about both axes design are explained in detail under this title.

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Symbols

P_r: Required axial force resistance for = required axial strength determined using LRFD or ASD load combinations, kips (N)
P_c: Strength of axial compressive force available according to Section EM_r: Required bending moment strength for = available axial strength, kips (N)
M_r = required flexural strength, determined using LRFD or ASD load combinations, kip-in. (N-mm)
M_c: current bending moment strength according to Section F = available flexural strength, kip- in. (N-mm)

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Design for Axial Force and Flexural Moment

• The strength calculation is made by taking into account considers the combined stresses created in the elements under flexural and axial force.

• The superposition of the stresses only applies to similar stresses.

• The superposition rule does not apply to stability losses.

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Design with AISC 360-16

Equation H1.1 is used for biaxial and single symmetry axis members under the influence of axial compression and flexural moment.

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• Mathinline
  body --uriencoded--$$ \normalsize \mathrm%7BWhen%7D \;\; \dfrac%7BP_r%7D%7BP_c%7D \ge 0.2 \;\;\;\;\;\;\;\;\;\;\; \dfrac%7BP_r%7D%7BP_c%7D + \dfrac%7B8%7D%7B9%7D \bigg(\dfrac%7BM_%7Brx%7D%7D%7BM_%7Bcx%7D%7D+\dfrac%7BM_%7Bry%7D%7D%7BM_%7Bcx%7D%7D \bigg) \le1.0 \;\;\;\;\;\;\;\;\;\;\;\;\;\; \;\;\;\;\;\;\;\;\;\;\;\;\;\; (H1-1a) $$

• Mathinline
  body --uriencoded--$$ \normalsize \mathrm%7BWhen%7D \;\; \dfrac%7BP_r%7D%7BP_c%7D \ge 0.2 \;\;\;\;\;\;\;\;\;\;\; \dfrac%7BP_r%7D%7B2P_c%7D + \bigg(\dfrac%7BM_%7Brx%7D%7D%7BM_%7Bcx%7D%7D+\dfrac%7BM_%7Bry%7D%7D%7BM_%7Bcx%7D%7D \bigg) \le1.0 \;\;\;\;\;\;\;\;\;\;\;\;\;\; \;\;\;\;\;\;\;\;\;\;\;\;\;\; (H1-1b) $$

Flexural design is explained under the title of Design of Steel Members for Flexure per AISC 360-16 §F

Compression design is explained under the title of Design of Steel Members for Compression per AISC 360-16 §E

• Design axial strength,

  Mathinline
  body $$ \normalsize P_c =\phi_c P_n $$

  (LRFD)

• Allowable axial strength

  Mathinline
  body $$ \normalsize P_c =P_n/ \Omega_c $$

  (ASD)

• Design flexural strength,

  Mathinline
  body $$ \normalsize M_c =\phi_b M_n $$

  (LRFD)

• Allowable flexural strength

  Mathinline
  body $$ \normalsize M_c =M_n/ \Omega_b $$

  (ASD)

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