• | -------- | ------- | ------- | -------------------- | -------------------- | | W8x31 | 9.13 | 3.47 | 2.02 | 383 | 335 | | W8x58 | 17.1 | 3.65 | 2.25 | 720 | 653 | | W10x33 | 9.71 | 4.17 | 1.09 | 414 | 234 | | W10x49 | 14.4 | 4.35 | 1.77 | 614 | 474 | | W10x68 | 20.0 | 4.44 | 2.07 | 855 | 715 | | W12x45 | 13.2 | 5.15 | 1.95 | 571 | 401 | | W12x65 | 19.1 | 5.28 | 3.02 | 829 | 738 | | W12x87 | 25.6 | 5.38 | 3.07 | 1114 | 993 | | W14x53 | 15.6 | 5.73 | 1.92 | 680 | 408 | | W14x68 | 20.0 | 5.82 | 2.44 | 872 | 639 | | W14x90 | 26.5 | 6.14 | 3.26 | 1167 | 1024 | | W14x120 | 35.3 | 6.24 | 3.44 | 1556 | 1387 | | W14x159 | 46.7 | 6.38 | 3.67 | 2054 | 1859 |

Note: phiPn values are approximate for KL = 12 ft (pin-ended, strong and weak axis). Actual capacity depends on effective length, end restraint, and intermediate bracing. Always verify with the Column Capacity Calculator.

UB / UC Column Capacities (AS 4100, Le = 3.6 m, Grade 300)

HEA/HEB Column Capacities (EN 1993, Lcr = 3.6 m, S355)

W-Shape Column Capacities (CSA S16:24, KL = 3.6 m, 350W)

Column Buckling Curves by Standard

AISC 360 Buckling Curves

AISC 360 uses a single column curve per section type (unlike EN 1993's multiple curves). The curve is built into Fcr equation:

AS 4100 Buckling Curves (Table 6.3.3(1))

EN 1993-1-1 Buckling Curves (Table 6.2)

CSA S16:24 Column Curves

CSA S16:24 uses the SSRC multiple column curve approach with exponent n:

Design Procedure Summary

AISC 360

1. Determine KL (effective length) and r_min for the section
2. Compute KL/r (slenderness ratio)
3. Compute Fe = pi^2 x E / (KL/r)^2
4. If KL/r <= 4.71 sqrt(E/Fy): Fcr = (0.658^(Fy/Fe)) x Fy; else: Fcr = 0.877 x Fe
5. Pn = Fcr x Ag; phiPn = 0.90 x Pn

AS 4100

1. Determine Le (effective length) and r
2. Compute lambda_n = (Le/r) x sqrt(kf) x sqrt(fy/250)
3. Determine alpha_b (from buckling curve), compute alpha_a = 2100 x (lambda_n - 13.5) / (lambda_n^2 - 15.3 x lambda_n + 2050)
4. Compute lambda = lambda_n + alpha_a x alpha_b
5. Determine alpha_c (from Table 6.3.3(2) or formula)
6. Nc = alpha_c x kf x An x fy; phiNc = 0.90 x Nc

EN 1993-1-1

1. Determine Lcr and i (radius of gyration)
2. Compute lambda = sqrt(A x fy / Ncr)
3. Select buckling curve and imperfection factor alpha
4. phi = 0.5 x (1 + alpha x (lambda - 0.2) + lambda^2)
5. chi = 1 / (phi + sqrt(phi^2 - lambda^2))
6. Nb,Rd = chi x A x fy / gamma_M1

CSA S16:24

1. Determine KL and r
2. Compute lambda = (KL/r) x sqrt(Fy / (pi^2 x E))
3. Cr = phi x A x Fy x (1 + lambda^(2n))^(-1/n)
4. phi = 0.90

Combined Compression and Flexure

All four codes also require interaction checks for columns subject to combined axial load and bending moment:

Effective Length (K) Factors

The effective length factor K accounts for end restraint conditions:

Use alignment charts (AISC CA-7.1, AS 4100 Fig 4.6.3.2) with column and beam stiffnesses for more precise K-factor determination. See the K-Factor Calculator for automated calculation.

Frequently Asked Questions

What is the difference between strong axis and weak axis buckling? Strong axis buckling (X-X axis) involves bending about the major axis with a larger radius of gyration rx, resulting in higher slenderness ratio KL/r and higher capacity. Weak axis buckling (Y-Y axis) uses the smaller radius of gyration ry and typically governs the column design. However, if lateral bracing is provided to the weak axis (e.g., wall girts or purlins), the effective buckling length for the weak axis reduces, and strong axis buckling may govern.

How does column effective length affect capacity? Doubling the effective length KL divides the Euler buckling load by four (capacity decreases with the square of length). A 12 ft column with K=1.0 buckling about the weak axis (ry = 2.02 in for W8x31) has KL/r = 71.3. Doubling to K=2.0 gives KL/r = 142.6, which is in the elastic buckling range. Adding intermediate braces that halve the unbraced length quadruples the Euler capacity.

When should I use ASD vs LRFD for column design? Both methods are acceptable in AISC 360. LRFD applies a resistance factor of phi_c = 0.90 to the nominal capacity. ASD divides nominal capacity by Omega_c = 1.67. LRFD provides more uniform reliability across different load scenarios and is increasingly preferred in US practice. AS 4100, EN 1993, and CSA S16 all use limit states design (LRFD equivalent).

What is the minimum slenderness ratio for a column? AISC 360 recommends KL/r <= 200 for primary compression members. AS 4100 limits Le/r <= 200 (Clause 6.3.3). EN 1993-1-1 has no explicit limit but higher lambda results in very low chi. CSA S16:24 limits KL/r <= 200. For secondary members such as wind bracing, K+sectionL/r <= 300 may be acceptable (AISC).

How does local buckling affect column capacity? AISC 360 addresses local buckling via Q (slenderness reduction factor) for slender sections. Q = Qs x Qa where Qs accounts for unstiffened elements (flanges) and Qa accounts for stiffened elements (webs). EN 1993 uses cross-section classification; Class 4 sections require effective width reduction per EN 1993-1-5. AS 4100 uses kf (form factor) — the ratio of effective area to gross area. CSA S16 uses the same Q factor approach as AISC.

Can W-shapes be used as columns or are UC/HE sections better? W-shapes (US) are widely used as columns in low-to-mid-rise construction. For taller buildings, W14 sections with deeper profiles and stockier flanges are preferred. UC sections (Australia/UK) have near-square proportions (h/b <= 1.2) that provide more balanced strong/weak axis capacity — ideal for columns. HEB sections (Europe) are also optimized for column use with similar h/b near unity. W-shapes with h/b > 1.3 are more efficient as beams but have weaker minor-axis column capacity.

What is the economic implication of choosing a heavier column section? Heavier columns (e.g., W14x159 vs W14x90) increase material cost but may simplify framing (fewer stiffeners, simpler connections). The cost premium is typically 15-30% for material plus 5-10% for connection savings. Optimal column design typically selects the lightest section that works, unless architectural constraints or column-to-beam connection standardization drives the selection.

Run This Calculation

→ Column Capacity Calculator — AISC 360, AS 4100, EN 1993, CSA S16 column design with interactive slenderness and combined loading checks.

→ Column Splice Design — column splice connection design including bearing plates, bolts, and welds per applicable code.

Try it now: Check your column capacity with our free Steel Column Capacity calculator →

Related Pages

• K-Factor Calculator — effective length factor determination
• Steel Column Design Example — full AISC worked example
• Column Buckling Equations — Euler, Johnson, and code-specific buckling formulas
• Column Splice Connection — column splice types and design guidance
• W-Shape Beam Sizes — complete section property database
• HEA/HEB Beam Sizes — European section properties
• Steel Grades Reference — A992, A572, S355, 300PLUS material properties

Design Resources

Calculator tools

• Column Capacity Calculator
• Column Splice Calculator
• Portal Frame Calculator
• Base Plate Design
• Beam Capacity Calculator

Design guides

• AISC Column Design Worked Example
• EN 1993 Column Buckling Example
• Steel Column Splice Guide
• Effective Length Guide

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