AISC 360-22
This page covers design checks to the AISC Specification for Structural Steel Buildings (ANSI/AISC 360-22) for I-sections, channels, tees, angles and HSS, in the standalone calculator and the FEA design tab. Both LRFD (Load and Resistance Factor Design) and ASD (Allowable Strength Design) are supported.
Open AISC 360-22 Calculator - Verification report
Standard Reference
| Standard | ANSI/AISC 360-22 (2022) |
| Design Methods | LRFD and ASD |
| Units | Calculator: kips, kip-ft, ksi, in; equation intermediates may use kip-in |
| Verification Source | AISC Manual Companion v16.0, Volume 1: Design Examples |
| Verification Cases | 42 published comparisons, 0.34% average numerical difference |
Supported Section Types
- I-Shapes (W, S, M, HP; rolled or welded built-up)
- Channels (C, MC)
- Tees (WT, ST, MT)
- Rectangular Hollow Sections (HSS rectangular and square)
- Circular Hollow Sections (Pipe, HSS round)
- Single Angles (equal and unequal leg)
Checks Performed
Each check in the design-check table reports the clause it applies. The checks are grouped as follows:
- Section classification (Table B4.1): Compression and flexural element classes are reported separately where they affect member checks.
- Tension (D2/D3): Gross yielding and effective-net-section rupture are checked; detailed bolt-hole paths are not inferred. Channels require an entered shear-lag factor U; without it, rupture and dependent tension interactions are INCOMPLETE. Confirm assumed shear-lag factors against the actual connection; defaults are not universally conservative. A valid tensile strength is required for rupture and dependent tension interactions.
- Compression (E3/E4/E5/E7): FEA member angles use E3 with recovered eccentric moments and H2 interaction; standalone angle calculators retain E5 eccentricity treatment. Both paths additionally check E4 when the longest full leg b/t exceeds 0.71√(E/Fy), using E7 effective area where required. For I-sections that need an E4 check, missing or invalid torsional or warping properties leave compression resistance unresolved, and the dependent compression-bending checks are not reported.
- Flexure (F2-F12): Flexural paths follow section family and axis. Channel major-axis bending requires compact webs and flanges; noncompact or slender channels have no major-axis resistance or dependent H1 interaction. Unequal-I major bending uses conservative F5 only where the compression flange is braced (continuous top-flange restraint under sagging moment, or both flanges braced), including both flange yielding limits, flange local buckling and web reduction. Other unequal-I major-axis flexure is not checked; the remaining checks are still reported.
- Shear (G2-G6): Web, flange, HSS, tee-stem, and single-angle shear rows report the applicable local shear path.
- Combined actions and torsion (App. 8 A-8-3 / H1/H2/H3): Compression-bending interactions include Appendix 8 B1 amplification for local member effects. P-Delta analysis retains frame sway and checks local member effects separately; section checks retain the full analysis moments. Where a P-Delta member has no first-order moment diagram (for example an internally subdivided member), B1 is applied to the P-Delta moments, which is conservative. Standalone moments are treated as first-order and receive B1. Invalid amplification prevents completion of the affected interaction. Frame sway amplification B2 and the complete Chapter C / Appendix 7 frame assessment remain separate. Closed-HSS torsion is checked when applied torsion is available.
Implemented 360-22 Deltas
- F6 minor-axis slender flange local buckling: uses the AISC 360-22 coefficient
0.70E/(b/tf)^2. - H3-6 HSS torsion interaction: uses both major- and minor-axis flexure ratios and takes
Vr/Vcas the larger x- or y-axis shear ratio. - F7 rectangular HSS local buckling: noncompact flange and web local buckling use the 360-22 interpolation between Mp and FyS with the Table B4.1b limits.
Design Inputs
The standalone calculator takes manually entered section dimensions or a section from the built-in US section library (manually entered I-shape, channel, tee and angle sections are calculated without root fillets), design actions and the inputs below. In the Structural FEA workflow, section geometry and material properties come from the member's assigned section and material, while design parameters are supplied per member. Calculator units are kips, kip-ft, ksi, in, with member lengths in ft.
Design Method
Select LRFD or ASD. The method sets the resistance or safety factors applied to the capacities.
Fabrication: for I-shapes, Hot Rolled or Welded / Built-up. Built-up affects flange classification, removes the G2.1(a) shear factor of 1.00 and triggers the E4 check. For HSS, ERW uses 0.93 tnom and SAW uses tnom. Optionally, I-shapes accept a different bottom flange (bf,bot and tf,bot).
Material Properties
| Symbol | Description | Unit |
|---|---|---|
Fy | Minimum yield stress | ksi |
Fu | Minimum tensile strength | ksi |
An | Optional net tension area after hole deductions; blank defaults to Ag. | in² |
U | Optional D3 shear-lag factor. Blank uses the section-family default (I-shapes 0.90 if bf ≥ 2d/3, otherwise 0.85, Table D3.1 Case 7; angles 0.80, Case 8; tees 0.85; HSS 0.75) except for channels, which return INCOMPLETE until U is entered | - |
Member Lengths And Bracing
| Input | Description | Unit/Basis |
|---|---|---|
Ky | Compression effective length factor about the weak/minor axis. The effective length is Ky × L; the standalone calculator takes KyL directly, blank = L. | - |
Kz | Compression effective length factor about the strong/major axis. The effective length is Kz × L; the standalone calculator takes KxL directly, blank = L. | - |
Lb | Member LTB length; blank = L. Not used for square or round HSS. | ft |
Kt / Lcz | Chapter E4 torsional/flexural-torsional factor (standalone: effective length), independent of KLT/Lb; blank = L. Not required where Cw = 0 (closed HSS/pipe, thin-wall angles). | - / ft |
Cb | LTB factor for the same sections as Lb, except tees (F9 has no Cb). Valid range 0.1 to 3.0 (1.5 for angles). Blank = calculated from the moment diagram in the FEA design tab, and 1.0 where KLT is not 1.0. In the standalone calculator a single moment entry is a uniform moment, so blank = 1.0 unless Quick Calc fills it. The calculator's Cantilever checkbox forces Cb = 1.0. | - |
KLT | FEA-tab factor where Lb = KLT x L. | - |
In the FEA Design tab these lengths are entered as factors on the member length: Kz, Ky, Kt and KLT.
Continuous restraint means the top flange is continuously restrained. Sagging (negative) major-axis moment compresses the restrained top flange and has no LTB reduction. Hogging (positive) moment compresses the unbraced bottom flange and is checked and reported separately by the unrestrained Chapter F method over Lb = KLT × L with the same Cb rules as an unbraced member. H1 interaction uses the flexural strength for the moment sign along the member. KLT = 0 declares the bottom flange braced as well, so neither moment sign has an LTB reduction. For single angles, continuous restraint applies to the whole member for both moment signs.
In the FEA Design tab the Cantilever control has three settings: Auto (default) follows the model and shows what it detected, for example "Auto (detected: cantilever, held at Node A)"; Span and Cantilever override the detection. On a cantilever the automatic Chapter F LTB checks use Cb = 1.0.
Design Actions
| Action | Description | Sign Convention |
|---|---|---|
P | Design axial force envelope | Compression or tension from the member forces; the applicable checks are made for each. |
Mz | Strong/major-axis bending moment | Tees: positive = hogging (stem in compression). Single angles: the sign sets the compression side. With continuous restraint: negative = sagging, positive = hogging. |
My | Weak/minor-axis bending moment | Weak (minor) axis moment. |
Vy | Major-axis shear demand | Paired with major-axis bending Mz. |
Vz | Minor-axis shear demand | Paired with minor-axis bending My. |
T | Torsion demand | Checked for closed HSS/pipe torsion when available. |
Resistance Factors
| Check | LRFD (φ) | ASD (Ω) |
|---|---|---|
| Tension (yielding) | 0.90 | 1.67 |
| Tension (rupture) | 0.75 | 2.00 |
| Compression | 0.90 | 1.67 |
| Flexure | 0.90 | 1.67 |
| Shear | 0.90 (1.00 for rolled I-shapes with h/tw ≤ 2.24 sqrt(E/Fy)) | 1.67 (1.50) |
| Torsion (H3, closed HSS) | 0.90 | 1.67 |
Limitations & Notes
- Analysis and amplification basis: Compression-bending checks include Appendix 8 B1 amplification (Eq. A-8-3) for local member effects in both linear and P-Delta FEA. In P-Delta FEA, B1 is applied to the member moment diagram without its local P-δ contribution, so frame sway comes from the analysis and local effects are not counted twice; section checks retain the full analysis moments. Where that diagram is unavailable, B1 is applied to the full analysis moments, which is conservative. Where αPr reaches the member elastic buckling load Pe1, B1 is undefined: the limit is reported and the affected interaction is not evaluated. Enter first-order moments in the standalone calculator; moments that already include local second-order effects would be amplified twice. Frame sway amplification B2 and the overall Chapter C or Appendix 7 stability assessment are checked separately.
- Member-strength scope: classification, tension, compression, flexure, shear, closed-HSS torsion, and combined actions are checked. Connection design is outside this member check.
- Connection/detail inputs not inferred: D3 HSS shear-lag Cases 5/6, D5 pin-connected members, D6 eyebars, and F13 bolt-hole proportioning require connection geometry and are checked separately.
- Member/detail geometry not inferred: E4(d)/(e) offset lateral bracing, G2.3 end-panel tension-field action, G2.4 stiffener design, and F11 rectangular bars/rounds require inputs or section families not present in this member tab.
- Combined axial force and biaxial bending (H1): H1.2 tension uses the governing Chapter D design strength, including net-section rupture. H1-1 adds the orthogonal moment ratios, including for round HSS; the resultant moment of round HSS is used only in the Chapter F8 flexural check.
- Angle LTB (F10): Principal-axis single-angle LTB uses F10-4, with the monosymmetry factor zero for equal angles and calculated from the geometry for unequal angles. Equal-angle geometric-axis bending uses F10-5 where applicable.
- Angle H2 stress points: The H2-1 interaction is evaluated at six points: the heel, the outer and inner tip of each leg, and the re-entrant corner. For single angles near capacity, confirm the principal-axis section properties and moment-axis assumptions against the AISC Manual tables.
- Angle compression (E4/E5): The coupled E4 check is calculated when b/t exceeds 0.71 sqrt(E/Fy), where b is the full width of the longer leg: E4-3 for equal angles and E4-4 for unequal angles. It is made in addition to E3 (FEA design tab, with the eccentric end moments from the analysis) or E5 (standalone calculator, leg ratio below 1.7), and the lower capacity is used in the H2 interaction.
- Plate girders (F4/F5): Doubly symmetric plate girders use F4 or F5. With continuous restraint, unequal-I sections use conservative F5 with tension-flange yielding (F5-10) where the compression flange is braced: under sagging moment, or under either moment sign with KLT = 0. Other unequal-I major-axis flexure, including hogging with only the top flange restrained, is not covered.
- Slender-web rectangular HSS (F7): F7 slender-web boxes are not covered when that bending axis is loaded; F7-7 is not implemented. Pure axial checks remain available.
- HSS wall thickness (B4.2): Fabrication sets the design wall thickness: ERW / cold-formed uses t = 0.93 tnom; SAW / hot-formed uses the full tnom. US library sections already store the AISC Manual design thickness and properties, so 0.93 is not applied again. For custom or non-US ERW sections t is reduced for slenderness, local buckling, shear and torsion; stored A, I, S and Z are used as entered.
- Custom-section axes: Check that the major and minor axes, moments of inertia, and elastic and plastic section moduli match the section preview. Incorrect axis assignments affect bending, buckling and LTB resistance.
- Channel major-axis bending: F2 is applied only where the web and flanges are compact. Noncompact or slender channels have no major-axis bending resistance or dependent H1 interaction; check those limit states separately. Independent axial, shear and minor-axis checks remain available.
- Required torsional buckling properties: For I-sections that need a Chapter E4 check, missing or invalid torsional or warping properties leave compression resistance unresolved: a limitation is reported and dependent compression-bending interactions are not reported. Passing flexural-buckling checks alone does not complete the member assessment.
- Net section: tension rupture and H1.2 interaction use the entered An and U. Blank An defaults to Ag; blank U uses the section-family default listed under the U input; channels need an entered U. Confirm U for the actual connection: assumed family values are not universally conservative. Bolt holes, staggered paths, connection length, and detailed shear-lag geometry are not inferred from the member model.
- Concentrated forces and reactions: AISC J10 local checks are not derived from FEA reactions, point loads, or connection forces. Check flange local bending, web local yielding, web crippling, web sidesway buckling, bearing stiffeners, and doubler plates separately.
- Design stiffness: resistance and stability checks use E = 29,000 ksi and G = 11,200 ksi as defined in the Specification. Material stiffness entered for structural analysis does not change these design values.
- Bracing design: effective lengths, unbraced lengths, restraint assumptions, and Cb overrides are design inputs. Brace strength, brace stiffness, diaphragm stiffness and attachment location are not verified.
- Torsion: H3.1/H3.2 closed-HSS torsion is checked where torsion demand is available. Torsion is not an input in the standalone calculator. Applied open-section torsion (H3.3) requires separate warping verification.
- Scope exclusions: ponding, fatigue, fire design, corrosion allowance, composite member design, seismic detailing/proportioning, and serviceability limits are outside this AISC member-strength check unless handled by a separate workflow.
Verification
The calculator is checked against 42 AISC Manual Companion v16.0 rows with an average numerical difference of 0.34%. The suite covers Chapter D tension, Chapter E compression, Chapter F flexure, Chapter G shear, and Chapter H interaction/torsion examples.