CSA S16 Canadian Steel Design
Perform factored resistance checks for structural steel members according to CSA S16-19. The calculator integrates Clause 11 classification, member stability, and Clause 13 interaction checks.
Design Check Overview
The calculator classifies your cross-section into Classes 1 through 4 based on Clause 11 width-to-thickness rules, then evaluates section and member resistances for tension, compression, bending, and shear. Where combined actions are present, interaction checks use the applicable Clause 13.8 or 13.9 path with the reported section properties and amplification factors.
Clause Compliance Coverage:
- Section classification (Cl 11.2 / Tables 1-2): Classification is action-specific and drives the section or effective-property branch.
- Tension (Cl 13.2): Gross yielding and net-section fracture are checked using optional member An and effective-net factor; blank An defaults to Ag because bolt-hole geometry is not inferred. Blank U uses the lowest Cl 12.3.3.2 value for open sections and 1.0 for hollow sections.
- Compression (Cl 13.3.1 / Cl 13.3.4): Member compression, supported flexural-torsional buckling, and Class 4 effective-area checks use the selected fabrication branch. Every Cr, including the Clause 13.8 section and member terms, uses the Table 1 effective area with Clause 11.3 widths; this is an engineering interpretation of S16-19, not an official CSA ruling.
- Flexure and LTB (Cl 13.5 / Cl 13.6.1 / Cl 14.3): Section paths follow the active section family. The 13.5(a) service-load yield condition for unequal-I and tee plastic resistance needs service actions, so it is reported as not checked; it is never inferred from the entered factored actions. With continuous restraint, major-axis Class 1/2 tees use full Z when the flange is compressed; when the stem tip is compressed (hogging), the 13.6.1 member check applies. Finite Class 1/2/3 tees use verified geometric beta and 13.6.1(e) member resistance, with My replacing Mp whenever the stem tip is compressed. Tee combined plastic eligibility remains limited. Class 4 tee, cantilever and destabilizing-load member methods and unsupported unequal-I LTB are not checked, and the dependent member checks are not reported. Non-square RHS receive the Clause 13.6.1 member LTB check with zero warping constant; SHS and CHS are exempt. Unrestrained cantilevers require rational analysis under Clause 13.6.1(d) and are omitted with a limitation notice; do not bypass this by switching the cantilever option off. The Clause 14.3.1 maximum web slenderness h/w <= 83000/Fy is checked, with an optional separate-analysis waiver. A reported PASS covers only performed checks.
- Shear (Cl 13.4 / Cl 14.6): Local shear paths are reported where applicable. CHS shear under 13.4.1.3 applies to Class 1/2 tubes only; Class 3/4 CHS shear is not checked. RHS shear uses the 13.4.1.1 web method with Aw = 2(D-4t)t, conservative relative to 13.4.1.3. Clause 14.6 shear-moment interaction applies to single-web beams (I-shapes and channels). Torsion is not an input and is not checked.
- Combined actions (Cl 13.8 / Cl 13.9): Compression-bending and tension-bending checks use the entered actions, including the applicable section, member, LTB and moment-only checks. Declare each frame direction as Braced, Unbraced or Unspecified under Clause 13.8.1. Braced directions apply U1 where required; unbraced directions use the entered moments with U1 = 1, and unspecified directions conservatively cover both conditions. The entered actions must include the applicable Clause 8.4 stability effects; this calculator does not run a frame analysis. Invalid amplification prevents completion of the affected interaction.
Supported Section Types
I-Shapes - W, WWF, S, HP
Channels - C, MC
Tees - WT, WWT
RHS / SHS
CHS / Pipe
Angles - L
Current Limitations
- Non-square RHS receive the Clause 13.6.1 member lateral-torsional buckling check with zero warping constant (Cw = 0), using the entered unbraced length. Square and circular hollow sections are exempt. A displayed PASS covers only the checks shown.
- Tension resistance under Cl 13.2 uses the entered An and U. Blank An defaults to Ag because holes are not inferred; blank U takes the lowest Cl 12.3.3.2 value for open sections and 1.0 for hollow sections (Cl 12.3.3.1). Check U against the actual connection.
- Single member analysis only: no automatic frame buckling analysis or system-level effects.
- The standalone calculator does not run a frame analysis or generate P-Delta moments. Declare each frame direction under Clause 13.8.1: unbraced directions use supplied moments with U1 = 1, braced directions apply U1 where required, and unspecified directions conservatively cover both conditions. Entered actions must include applicable Clause 8.4 stability effects; use the 3D FEA design check to obtain them from a P-Delta analysis. Invalid amplification gives FAIL or INCOMPLETE rather than a completed interaction check.
- No connection design, no composite construction, and no seismic provisions (Clause 27).
- CSA S16 local bearing, web local yielding, web crippling, web buckling, bearing-stiffener, and column force-transfer checks are not performed or derived from point loads, reactions, or connection forces. Check support bearing and concentrated load introduction regions separately.
- Effective length factors (K) must be user-specified (default 1.0). Unrestrained cantilevers require rational LTB analysis under Clause 13.6.1(d): with the cantilever option on, member LTB is reported as INCOMPLETE and must be designed by separate rational analysis. There is no rational-resistance input, and ω2/ω3 is only a moment factor. Do not switch the cantilever option off to obtain a result: the automatic ω2 for a cantilever moment diagram is unconservative.
- 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.
- Torsion is not an input in the standalone calculator. Use the 3D FEA design check for torsion on closed hollow sections (RHS/CHS). Applied open-section torsion requires separate warping analysis, and the Clause 14.10.4 service-load normal-stress limit is not checked.
Benchmarks: 44 published comparisons, 0.18% average numerical difference
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