Steel Column (ASD, AISC 360-22)

How it calculates

The Steel Column (ASD, AISC 360-22) calculator designs hot-rolled steel columns and posts using Allowable Stress Design per the latest edition of the AISC Specification. It runs a first-order structural analysis to determine service-level demands, then applies AISC 360-22 allowable capacity equations for all limit states.

Structural analysis

The calculator performs FEA on the column as a beam-column, resolving axial forces, moments, and deflections under service loads. End conditions (pinned, fixed, roller) are specified at each support. Concentrated axial and distributed lateral loads can be applied at any height. A first-order moment amplification factor accounts for P-delta effects; the member is assumed to be part of a braced frame.

Axial compression capacity

Allowable axial compressive strength follows AISC 360-22 Chapter E:

utilization = Pa / (Pn / Omega_c) ≤ 1.0

where Omega_c = 1.67. The nominal compressive strength Pn is governed by flexural buckling for doubly-symmetric shapes. For singly-symmetric and unsymmetric sections, flexural-torsional buckling is additionally evaluated. Slender element Q factors are applied per Section E7 where local buckling reduces the available strength.

Flexural capacity

Moment demands from eccentricity or lateral loads are checked per AISC 360-22 Chapter F:

utilization = |Ma| / (Mn / Omega_b) ≤ 1.0

where Omega_b = 1.67. Compact, non-compact, and slender section classifications per Table B4.1b govern the applicable strength equations. Lateral-torsional buckling is evaluated against the unbraced length and limiting lengths Lp and Lr.

Combined axial compression and bending

The AISC H1-1 interaction check (ASD form) covers simultaneous axial and biaxial bending:

• For Pa * Omega_c / Pn ≥ 0.2: (Pa * Omega_c / Pn) + (8/9) * (Mxa * Omega_b / Mnx + Mya * Omega_b / Mny) ≤ 1.0
• For Pa * Omega_c / Pn < 0.2: (Pa * Omega_c / 2Pn) + (Mxa * Omega_b / Mnx + Mya * Omega_b / Mny) ≤ 1.0

Both strong- and weak-axis moments are included in the interaction check.

Axial deformation

Axial shortening under service loads is calculated and reported alongside strength checks for serviceability review.

Outputs

Results are displayed as colour-coded utilization ratios for each limit state with code clause references. The governing check, critical load case, and section properties are summarised for report documentation and QA review.