United StatesAISC 360-22
Member reactions link to connected column or footing calculations automatically, change a load and everything downstream updates. Design steel members to the current AISC 360-22 LRFD specification with combined axial and bending interaction, lateral-torsional buckling, and flexural buckling checks for US hot-rolled and HSS sections.
Method & scope
Calculation method
The Steel Member (Design Only, LRFD) calculator to AISC 360-22 accepts factored design forces from analysis and runs all LRFD member capacity checks for the selected US steel section.Section classification
Plate element slenderness ratios (b/t for flanges, h/tw for webs) are compared to the limiting values from AISC 360-22 Table B4.1a (compression) and B4.1b (flexure). Compact, non-compact, and slender classifications are determined automatically for each element. Slender elements trigger effective width reductions for compression and modified flexural strength equations.Flexural capacity and lateral-torsional buckling
Chapter F provisions govern flexure. For W-shapes and doubly-symmetric I-sections, the plastic moment Mp sets the upper bound. Lateral-torsional buckling reduces capacity when the unbraced length Lb exceeds Lp (onset of LTB). The calculator determines the limit states boundaries:- Lb ≤ Lp: Mn = Mp (plastic, no LTB reduction)
- Lp < Lb ≤ Lr: linear LTB interpolation
- Lb > Lr: elastic LTB governs, Mn = Fcr × Sx
Compression and buckling
Chapter E covers flexural buckling about both principal axes and, for non-symmetric sections, flexural-torsional buckling. The slenderness ratio KL/r is evaluated for each axis. The critical stress Fcr is derived from: φcPn = 0.9 × Fcr × Ag For slender element sections, the effective area Aeff accounts for local buckling, and Fcr is computed on the basis of Aeff/Ag. Torsional and flexural-torsional buckling provisions apply for sections with low torsional stiffness such as double angles and tees.Combined actions interaction
Chapter H interaction equations are the core result. For Pr/Pc ≥ 0.2 (high axial): interaction ratio = Pr/Pc + (8/9)(Mrx/Mcx + Mry/Mcy) ≤ 1.0 For Pr/Pc < 0.2 (low axial): interaction ratio = Pr/(2Pc) + (Mrx/Mcx + Mry/Mcy) ≤ 1.0 Each term is shown with its available and required strength values, so the relative contribution of axial and bending demands is immediately visible.P-delta and stability
A first-order moment amplification factor is used to account for P-little delta effects within the member. The member is assumed to be part of a braced frame. Second-order effects at the frame level should be confirmed before applying this calculator.Shear
Chapter G shear checks determine Vn from the product of the shear area and the shear coefficient Cv2. For compact webs Cv2 = 1.0. For slender webs the coefficient is reduced and tension-field action may be considered for interior panels.How to use it
1
Open the calculator
Open it from Run calc in the About this calculator panel above.
2
Enter your inputs
Work through the input sections from top to bottom. Click any input label to see its reference explanation, clause, conditions and assumptions. See Checks, References, Conditions and Assumptions.
3
Review the results and export
Check the utilization of each governing check in the summary, then export a PDF report. See Views and Export.
Common questions
What design method and code does this calculator use?
What design method and code does this calculator use?
This calculator uses the Load and Resistance Factor Design (LRFD) method to AISC 360-22, the 2022 edition of the AISC Specification for Structural Steel Buildings. It is the current recommended version for new US projects using LRFD. For ASD design to the same code edition, use the steelMemberASDAISC360-22 calculator.
What are the key inputs?
What are the key inputs?
You provide the section size (W, HSS, pipe, channel, or angle), member length, effective length factors or unbraced lengths for each axis, and the factored design forces, axial load, major- and minor-axis bending moments, and shear. Forces can be entered manually or linked directly from an analysis calculator.
What limit states does it check?
What limit states does it check?
The calculator checks yielding and lateral-torsional buckling for flexure (Chapter F), flexural and torsional buckling for compression (Chapter E), tensile yielding and rupture (Chapter D), shear (Chapter G), and the combined axial plus bending interaction equations from AISC 360-22 Chapter H. Compact, non-compact, and slender section classifications apply automatically based on b/t ratios.
Can it handle combined axial load and biaxial bending?
Can it handle combined axial load and biaxial bending?
Yes. The Chapter H interaction equations handle simultaneous axial force and bending about one or both axes. The calculator determines whether the high-axial or low-axial form governs (Pr/Pc ≥ 0.2 or < 0.2) and reports the controlling interaction ratio with code reference.
How do I set the effective length and unbraced length?
How do I set the effective length and unbraced length?
Effective length factors K are entered for strong- and weak-axis buckling separately, and the unbraced length Lb is set for lateral-torsional buckling. The calculator derives Lp and Lr from section properties automatically. The braced-frame assumption is used, with first-order moment amplification applied for P-delta effects within the member.
Can this member calculation link to beam and footing calculations?
Can this member calculation link to beam and footing calculations?
Yes, the member calc receives reactions from upstream calculations (e.g. frame analysis) and passes base reactions to footing or base plate calculations. Changes propagate automatically through the load path.
Next steps
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