Professional AS 4100:2020 Structure Analysis
Evaluate structural steel member capacities according to AS 4100:2020. This calculator automates section slenderness, member stability, and combined action interactions.
Design Check Overview
The calculator classifies your cross-section as Compact, Non-compact, or Slender based on plate width-to-thickness ratios and residual stress category. It then determines section capacities (tension, compression, bending, shear) and member stability accounting for effective lengths, buckling curves, and lateral-torsional buckling. Where multiple actions are present, combined interaction checks are performed automatically.
Clause Compliance Coverage:
- Section classification (Table 5.2 / Cl 6.2.4): Bending classification and compression form-factor effects are selected from the active section state.
- Tension (Cl 7.2): Gross yielding and net-section fracture are checked using optional member An; blank An defaults to Ag because fastener-hole geometry is not inferred.
- Compression (Cl 6.2 / Cl 6.3.3): Ordinary major/minor flexural buckling is checked. The additional FTB mode is numerical for fabricated unequal-flange I-sections, fabricated equal-flange channels, and minor-axis-braced hot-rolled channels; unequal-flange fabricated channels remain incomplete.
- Flexure (Cl 5.2 / Cl 5.6): Section bending and LTB member bending checks use the selected section orientation and restraint inputs.
- Shear (Cl 5.11.3-Cl 5.11.5 / Cl 5.12.3): Shear, shear buckling, non-uniform shear, and shear-moment rows report the active local path.
- Bearing (Cl 5.13 / Cl 6.3.3): Optional local bearing checks are reported when R*, bearing length, distance from the member end, and restraint inputs are supplied; RHS/SHS bending-bearing interaction is included where applicable.
- Combined actions (Cl 4.4.2 / Cl 8.3 / Cl 8.4): Section and member axial-plus-bending checks are reported with the applicable compression or tension branch. Linear-analysis compression interactions use station-concurrent delta_b amplification; N*/Nomb at or above 1.0, or invalid amplification inputs, fail closed. P-Delta moments are not amplified again.
Supported Section Types
I-Shapes - UB, UC, WB, WC
Channels - PFC
Tees - UBT
RHS / SHS
CHS
Angles - EA, UA
Current Limitations
- Tension fracture under Cl 7.2 uses the entered An and kt. Blank An defaults to Ag and blank kt defaults to 1.0 because connection geometry is not inferred.
- Single member analysis only: no automatic frame buckling analysis or system-level effects.
- The entered M* values are treated as design moments. This standalone calculator does not declare a frame-analysis basis and does not add Clause 4.4.2 δb; include any required second-order or moment-amplification effects in the entered actions. In the Structural FEA Design tab, linear analysis applies δb and fails closed at an invalid denominator, while P-Delta moments are not amplified again.
- No connection design, no composite construction (AS 2327), and no fatigue checks.
- Effective length factors (ke) must be user-specified (default 1.0). Moment modification factor (αm) may be entered directly or filled from the beam statics helper.
- The calculator assumes the default section orientation shown in the preview. Major and minor axis inputs are relative to that orientation. Rotated or sideways mono-symmetric members, such as channels, tees, and angles, should be checked in the FEA workflow.
- Clause 6.3.3 ordinary major/minor flexural buckling is checked for all supported compression members. Its additional flexural-torsional mode is evaluated locally for fabricated unequal-flange I-sections, fabricated equal-flange channels, and hot-rolled channels with confirmed minor-principal-axis bracing, using the referenced AS/NZS 4600 equations, the AS 4100 reduction of 0.85, and phi = 0.90. Fully non-symmetric fabricated sections remain incomplete where validated principal-axis and shear-centre properties are unavailable.
- Optional Cl 5.13 bearing checks are available for I-shapes, channels, and RHS/SHS when local bearing inputs are supplied. The calculator does not infer R*, bearing length, bearing location, or web restraint from V*; load-bearing stiffeners, end posts, and web stiffener detailing remain separate checks.
- Torsion is not an input in the standalone calculator. In the FEA tool, torsion (Bredt-Batho) is checked for closed hollow sections (RHS/SHS/CHS) only; warping torsion for open sections is not performed.
Benchmarks: 60 independent test cases, 0.17% average difference
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