Steel Column (CSA S16:19)

How it calculates

The Steel Column (CSA S16:19) calculator designs hot-rolled steel columns and posts using limit state design per CSA S16:19 with load combinations per NBCC 2015. It runs a structural analysis to determine factored demands, then applies CSA S16:19 capacity equations for all limit states.

Structural analysis

The calculator performs FEA on the column as a beam-column, resolving axial forces, bending moments, and deflections under applied loads. End conditions (pinned, fixed, roller) are specified at each support. Concentrated axial loads and distributed lateral loads can be applied at any height. The member is assumed straight and prismatic (non-tapered) with a uniform cross-section along its full height. The member is treated as part of a braced frame; K-factors for sway frames should be derived from a rational analysis.

Section classification

Cross-sections are classified as Class 1, 2, 3, or 4 per CSA S16:19 Table 1 based on the flange and web width-to-thickness ratios under the combination of axial load and bending. Class 1 and 2 sections reach full plastic moment; Class 3 sections are limited to the yield moment. Class 4 sections are not supported - where a Class 4 result is determined the check will show as failing.

Axial compressive resistance

Axial compressive resistance Cr follows CSA S16:19 Clause 13.3:

utilization = Cf / Cr ≤ 1.0

Cr = phi * A * fy * (1 + lambda^(2n))^(-1/n), where lambda is the modified slenderness and n = 1.34 for hot-rolled sections. Major- and minor-axis effective lengths are evaluated separately to find the governing buckling axis.

Flexural resistance

Factored moment resistance Mr follows CSA S16:19 Clause 13.5:

utilization = |Mf| / Mr ≤ 1.0

For laterally supported members Mr = phi * Mp or phi * My depending on section class. For unsupported lengths exceeding Lu, lateral-torsional buckling reduces Mr per the omega_2-modified curve. Strong- and weak-axis moment resistances are evaluated independently.

Combined axial and bending

Combined axial compression and biaxial bending interaction follows CSA S16:19 Clause 13.8. The interaction checks for both cross-section and overall member stability are performed. The checks apply to columns with simultaneous axial and moment demands from gravity, wind, or seismic load combinations.

Outputs

Results are displayed as colour-coded utilization ratios for each limit state with CSA S16:19 clause references. Section class, governing demands, capacity values, and resistance factors are tabulated for report documentation.