CSA S16-19

The CSA S16-19 engine implements CSA S16-19 - Design of Steel Structures, the Canadian standard for the design of steel structures. It supports Class H (hot-formed/stress-relieved) and Class C (cold-formed) fabrication types for hollow sections.

Open CSA S16-19 Calculator

Standard Reference

Supported Section Types

• I-Shapes (W-shapes, WWF - rolled and welded wide flanges)
• Channels
• Tees (WT - beam tees and column tees with stem compression detection)
• Rectangular Hollow Sections (HSS rectangular and square - Class H and Class C)
• Circular Hollow Sections (HSS round - Class H and Class C)
• Angles (equal and unequal leg)

Checks Performed

The design-check table shows the specific row and clause used for each member result. The documentation keeps the same clause groups at a summary level:

• 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.
• 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.
• Flexure and LTB (Cl 13.5 / Cl 13.6): Section bending, LTB, tee, angle, and biaxial bending rows use the active section family path.
• Shear and torsion (Cl 13.4 / Cl 14.6 / Cl 14.10): Local shear paths, plate-girder shear-moment interaction, and closed-section torsion are reported where applicable.
• Combined actions (Cl 13.8 / Cl 13.9): Compression-plus-bending and tension-plus-bending paths use station-coincident demands. Non-P-Delta compression interaction uses U1; Cf/Ce at or above 1.0, or invalid amplification inputs, fails closed and suppresses the interaction. P-Delta moments are not amplified again.

Calculator Inputs

The standalone CSA S16-19 calculator accepts the following inputs. All values are in metric units.

Fabrication Type

Select the fabrication method - this affects the compression branch and section classification:

• Rolled - standard rolled sections (W, C, WT, angles)
• Class H - hot-formed or stress-relieved HSS
• Class C - cold-formed HSS

Section Geometry

Select a shape group, then enter dimensions or pick from the built-in section library (CISC shapes).

Material Properties

Member Lengths & Bracing

The explicit Cantilever switch forces ω₂/ω₃ to 1.0and ignores the applicable typed ω₂ or ω₃ override while enabled. Turn it off only when applying a rational cantilever LTB result through the manual inputs.

A Continuously Restrained checkbox bypasses the LTB check. For single angles it also switches the bending-resistance path from principal-axis Cl. 13.6(g) to geometric-axis Cl. 13.5(d), since Cl. 13.6(g) only applies to angles without continuous lateral-torsional restraint. L_u, the applicable ω₂/ω₃ override, and the cantilever LTB input are inactive while continuous restraint is enabled.

Design Actions

Capacity Reduction Factor

The engine applies CSA S16 resistance factors internally. Result details and handcalc output report the governing factor used by each emitted check.

Fabrication Types

Class 4 Effective Section Properties

Class 4 sections use reduced effective properties per Clause 13.3.4 (compression) and 13.5(c) (flexure). Result details report the effective area, effective section modulus, or effective yield value used by the governing check.

• I-shapes & channels: Effective area and effective section modulus are computed from the gross section while reducing only the relevant slender compression elements.
• Tees: Class 4 output reflects the active stem stress state and the governing station branch used by the emitted check.
• Angles: Class 4 single-angle checks use the Clause 11.3.1(b) effective-area basis and the Clause 13.5(d) effective-yield branch where applicable.
• RHS/SHS: Effective flat widths follow the Clause 11.3.2(b) convention. Axial compression preserves gross corner area and reduces only ineffective flat strips; bending and interaction checks use the active station stress state where applicable.
• Minor-axis I-shape bending: Effective section modulus uses the appropriate local flange outstand reduction for the weak-axis case.

Section Classification (Clause 11.2)

Per Clause 11.2, Table 1 applies to members subject to axial compression, while Table 2 applies to elements in flexure or combined flexure and compression. The web interaction limits are used only for the Table 2 rows that require them. RHS/SHS checks use the Cl. 11.3.2(b) flat-width convention and the active station stress state for Class 4 bending or 13.8.4 interaction output.

Limitations & Notes

• Analysis and amplification basis: Linear/non-P-Delta compression interaction, including the standalone calculator, uses Clause 13.8 U₁. C_f/C_e at or above 1.0 gives an axis-specific FAIL; invalid E/I/K/L inputs give INCOMPLETE, and the affected compression interaction is suppressed. Structural FEA P-Delta moments are used directly and are not amplified again.
• Custom-section axis convention: The engine expects section properties in the AutoCalcs strong/weak convention: Izz is major/strong-axis inertia and Iyy is minor/weak-axis inertia. In raw section-library files, Szz/Syy are plastic section modulus values, not elastic Sx/Sy; the loader may expose those plastic values internally as Pzz/Pyy. Displayed/report Sx/Sy elastic values are derived separately from Wel fields or geometry/inertia. Custom or imported sections with these axes swapped can produce incorrect bending, buckling, and LTB axis assignments.
• Net section: Tension resistance under Cl 13.2 uses entered A_n and U; blank A_n defaults to A_g and blank U defaults to 1.0. Bolt holes, staggered paths, and connection shear-lag geometry are not inferred.
• Unequal-leg angle LTB: Uses the Clause 13.6(g)(ii) angle branch and applies the standard sign convention based on long-leg compression.
• Transverse-load moment amplification: Linear moment diagrams use the applicable end-moment path. Transverse-load cases use a conservative default.
• Cantilever moment factor: The cantilever switch forces ω₂/ω₃ = 1.0; turn it off only when applying a rational cantilever LTB result through the manual inputs.
• WWF detection: Welded wide flanges are auto-detected from the section description and assigned the Class H compression branch.
• Concentrated forces and reactions: The CSA S16 member engine does not perform local bearing, web local yielding, web crippling, web buckling, bearing-stiffener, or column force-transfer checks, and it does not derive these checks from FEA reactions, point loads, or connection forces. Check support bearing and concentrated load introduction regions separately from the member-strength result.
• Torsion (14.10): Not an input in the standalone calculator. In the model workflow, torsion is checked for closed hollow sections (RHS/CHS) only. Warping torsion for open sections (I-beams, channels, angles, tees) is not performed.
• Tee LTB centroid: Tee LTB uses a geometry-derived centroid for the flange and stem.
• Tee effective yield (Cl. 13.5(c)): The reported value is the value used by the governing emitted check. It reflects the active stress-state branch for that check and should not be read as a single global member class.
• Angle effective yield (Cl. 13.5(d)(ii)): Applied for Class 4 single-angle bending where the clause branch requires it.
• RHS shear area: Uses the clear flat-width convention for hollow-section wall shear.
• Serviceability and special design states: Structural analysis results may report displacements separately, but the CSA S16 design engine does not perform serviceability limit comparisons, vibration checks, fatigue, fire, corrosion/durability, connection detailing, or execution checks unless handled by a separate workflow.

Verification

The engine is benchmarked against 50 independent test cases from published steel design examples and independent verification benchmarks, with an average difference of 0.16%.