Concentrated load on a beam web
Verified against CSA S16-19, AISC 360-22 and CISC SST 12.1, 2026-09-29
Web yielding, crippling and sidesway buckling of a W shape, and bearing stiffeners, to CSA S16. Check a W shape under a concentrated load or a support reaction, at its end or inside the span. The unstiffened web is checked for local yielding, crippling and sidesway buckling; a pair of bearing stiffeners is checked with its strip of web as a column, for bearing on the flange, and for its welds to the web.
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This printed copy omits the derivation. The full report, with every step, is the PDF at https://calc.struct.work/calc/concentrated-load.pdf.
Checks
| Check | D/C | Utilisation | Result |
|---|---|---|---|
| Web slenderness ok\(\frac{\htmlClass{sym-h}{h}}{\htmlClass{sym-w}{w}} \cdot \frac{\htmlClass{sym-F_y}{F_{y}}}{1\ \mathrm{MPa}} \leq 83000 \quad \Rightarrow \quad \frac{\htmlClass{sym-h}{225\ \mathrm{mm}}}{\htmlClass{sym-w}{7.4\ \mathrm{mm}}} \cdot \frac{\htmlClass{sym-F_y}{350\ \mathrm{MPa}}}{1\ \mathrm{MPa}} \leq 83000\) | 0.13 | PASS | |
| Stiffener outstand ok\(\frac{\frac{\htmlClass{sym-b_1}{b_{1}}}{\htmlClass{sym-t_1}{t_{1}}} \cdot \sqrt{\htmlClass{sym-F_y1}{F_{y1}} \cdot 1\ \mathrm{MPa}}}{1\ \mathrm{MPa}} \leq 200 \quad \Rightarrow \quad \frac{\frac{\htmlClass{sym-b_1}{80\ \mathrm{mm}}}{\htmlClass{sym-t_1}{10\ \mathrm{mm}}} \cdot \sqrt{\htmlClass{sym-F_y1}{300\ \mathrm{MPa}} \cdot 1\ \mathrm{MPa}}}{1\ \mathrm{MPa}} \leq 200\) | 0.69 | PASS | |
| Stiffened ok\(\htmlClass{sym-P_f}{P_{f}} \leq \htmlClass{sym-C_r}{C_{r}} \quad \Rightarrow \quad \htmlClass{sym-P_f}{400\ \mathrm{kN}} \leq \htmlClass{sym-C_r}{609.3\ \mathrm{kN}}\) | 0.66 | PASS |
Results
| Quantity | Description | Value | Unit |
|---|---|---|---|
| \(\htmlClass{sym-B_r}{B_{r}}\) | Bearing resistance without stiffeners | 206.2 | \(\mathrm{kN}\) |
| \(\htmlClass{sym-C_r}{C_{r}}\) | Bearing resistance with stiffeners | 609.3 | \(\mathrm{kN}\) |
| \(\htmlClass{sym-B_r4}{B_{r4}}\) | Flange local bending, a tensile force | 133.4 | \(\mathrm{kN}\) |
| \(\htmlClass{sym-B_r5}{B_{r5}}\) | Web buckling, forces on both flanges | 200.1 | \(\mathrm{kN}\) |
Derivation
S16 Cl. 14.3.2
\[\begin{aligned} \htmlClass{sym-B_r1}{B_{r1}} &= \htmlClass{sym-phi_be}{\phi_{\mathrm{be}}} \cdot \htmlClass{sym-w}{w} \cdot \left(\htmlClass{sym-N}{N} + 4 \cdot \htmlClass{sym-t}{t}\right) \cdot \htmlClass{sym-F_y}{F_{y}} \\ &= \htmlClass{sym-phi_be}{0.75} \cdot \htmlClass{sym-w}{7.4\ \mathrm{mm}} \cdot \left(\htmlClass{sym-N}{250\ \mathrm{mm}} + 4 \cdot \htmlClass{sym-t}{11\ \mathrm{mm}}\right) \cdot \htmlClass{sym-F_y}{350\ \mathrm{MPa}} \\ &= 571.1\ \mathrm{kN} \end{aligned}\]S16 Cl. 14.3.2
\[\begin{aligned} \htmlClass{sym-B_r2}{B_{r2}} &= 0.6 \cdot \htmlClass{sym-phi_be}{\phi_{\mathrm{be}}} \cdot \htmlClass{sym-w}{w}^{2} \cdot \sqrt{\htmlClass{sym-F_y}{F_{y}} \cdot \htmlClass{sym-E}{E}} \\ &= 0.6 \cdot \htmlClass{sym-phi_be}{0.75} \cdot \left(\htmlClass{sym-w}{7.4\ \mathrm{mm}}\right)^{2} \cdot \sqrt{\htmlClass{sym-F_y}{350\ \mathrm{MPa}} \cdot \htmlClass{sym-E}{200\ \mathrm{GPa}}} \\ &= 206.2\ \mathrm{kN} \end{aligned}\]Branch: \(M_{f} < M_{y}\) held
Branch: \(\alpha \leq 2.3\) held
AISC J10.4 (a)
\[\begin{aligned} \htmlClass{sym-B_r3}{B_{r3}} &= \frac{0.85 \cdot \htmlClass{sym-C_rs}{C_{\mathrm{rs}}} \cdot \htmlClass{sym-w}{w}^{3} \cdot \htmlClass{sym-t}{t}}{\htmlClass{sym-h_c}{h_{c}}^{2}} \cdot \left(1 + 0.4 \cdot \htmlClass{sym-alpha}{\alpha}^{3}\right) \\ &= \frac{0.85 \cdot \htmlClass{sym-C_rs}{6.62\ \mathrm{TPa}} \cdot \left(\htmlClass{sym-w}{7.4\ \mathrm{mm}}\right)^{3} \cdot \htmlClass{sym-t}{11\ \mathrm{mm}}}{\left(\htmlClass{sym-h_c}{183\ \mathrm{mm}}\right)^{2}} \cdot \left(1 + 0.4 \cdot \htmlClass{sym-alpha}{0.8326}^{3}\right) \\ &= 921.9\ \mathrm{kN} \end{aligned}\]S16 Cl. 21.3 (b), halved at the end by AISC J10.1
\[\begin{aligned} \htmlClass{sym-B_r4}{B_{r4}} &= \frac{0.9 \cdot 7 \cdot \htmlClass{sym-t}{t}^{2} \cdot \htmlClass{sym-F_y}{F_{y}}}{2} \\ &= \frac{0.9 \cdot 7 \cdot \left(\htmlClass{sym-t}{11\ \mathrm{mm}}\right)^{2} \cdot \htmlClass{sym-F_y}{350\ \mathrm{MPa}}}{2} \\ &= 133.4\ \mathrm{kN} \end{aligned}\]AISC J10.5, halved at the end
\[\begin{aligned} \htmlClass{sym-B_r5}{B_{r5}} &= \frac{0.9 \cdot 12 \cdot \htmlClass{sym-w}{w}^{3} \cdot \sqrt{\htmlClass{sym-E}{E} \cdot \htmlClass{sym-F_y}{F_{y}}}}{\htmlClass{sym-h_c}{h_{c}}} \\ &= \frac{0.9 \cdot 12 \cdot \left(\htmlClass{sym-w}{7.4\ \mathrm{mm}}\right)^{3} \cdot \sqrt{\htmlClass{sym-E}{200\ \mathrm{GPa}} \cdot \htmlClass{sym-F_y}{350\ \mathrm{MPa}}}}{\htmlClass{sym-h_c}{183\ \mathrm{mm}}} \\ &= 200.1\ \mathrm{kN} \end{aligned}\]S16 Cl. 14.4.2, 12 w of web
\[\begin{aligned} \htmlClass{sym-A_0}{A_{0}} &= 12 \cdot \htmlClass{sym-w}{w}^{2} + 2 \cdot \htmlClass{sym-t_1}{t_{1}} \cdot \htmlClass{sym-b_1}{b_{1}} \\ &= 12 \cdot \left(\htmlClass{sym-w}{7.4\ \mathrm{mm}}\right)^{2} + 2 \cdot \htmlClass{sym-t_1}{10\ \mathrm{mm}} \cdot \htmlClass{sym-b_1}{80\ \mathrm{mm}} \\ &= 2257\ \mathrm{mm}^{2} \end{aligned}\]S16 Cl. 13.3.1, n = 1.34
\[\begin{aligned} \htmlClass{sym-C_r1}{C_{r1}} &= 0.9 \cdot \htmlClass{sym-A_0}{A_{0}} \cdot \htmlClass{sym-F_ye}{F_{\mathrm{ye}}} \cdot \left(1 + \htmlClass{sym-lambda_s}{\lambda_{s}}^{2 \cdot 1.34}\right)^{\frac{-1}{1.34}} \\ &= 0.9 \cdot \htmlClass{sym-A_0}{2257\ \mathrm{mm}^{2}} \cdot \htmlClass{sym-F_ye}{300\ \mathrm{MPa}} \cdot \left(1 + \htmlClass{sym-lambda_s}{0.04999}^{2 \cdot 1.34}\right)^{\frac{-1}{1.34}} \\ &= 609.3\ \mathrm{kN} \end{aligned}\]S16 Cl. 13.13.2.2, weld metal
\[\begin{aligned} \htmlClass{sym-V_r1}{V_{r1}} &= 4 \cdot 0.67 \cdot \htmlClass{sym-phi_w}{\phi_{w}} \cdot 0.707 \cdot \htmlClass{sym-D}{D} \cdot \htmlClass{sym-h_c}{h_{c}} \cdot \htmlClass{sym-X_u}{X_{u}} \\ &= 4 \cdot 0.67 \cdot \htmlClass{sym-phi_w}{0.67} \cdot 0.707 \cdot \htmlClass{sym-D}{6\ \mathrm{mm}} \cdot \htmlClass{sym-h_c}{183\ \mathrm{mm}} \cdot \htmlClass{sym-X_u}{490\ \mathrm{MPa}} \\ &= 683\ \mathrm{kN} \end{aligned}\]S16 Cl. 13.10 (a), clear of the fillet
\[\begin{aligned} \htmlClass{sym-V_r3}{V_{r3}} &= 0.9 \cdot 1.5 \cdot \htmlClass{sym-F_ye}{F_{\mathrm{ye}}} \cdot 2 \cdot \left(\htmlClass{sym-b_1}{b_{1}} - \left(\htmlClass{sym-k}{k} - \htmlClass{sym-t}{t}\right)\right) \cdot \htmlClass{sym-t_1}{t_{1}} \\ &= 0.9 \cdot 1.5 \cdot \htmlClass{sym-F_ye}{300\ \mathrm{MPa}} \cdot 2 \cdot \left(\htmlClass{sym-b_1}{80\ \mathrm{mm}} - \left(\htmlClass{sym-k}{32\ \mathrm{mm}} - \htmlClass{sym-t}{11\ \mathrm{mm}}\right)\right) \cdot \htmlClass{sym-t_1}{10\ \mathrm{mm}} \\ &= 477.9\ \mathrm{kN} \end{aligned}\]Questions
Why is AISC used for sidesway web buckling?
S16 has no clause for it, so the calc takes AISC 360 Section J10.4, which applies when the tension flange is not restrained at the load.
When does AISC J10.4 sidesway web buckling not apply?
When (h/w)/(L/b) exceeds 2.3 with the compression flange restrained against rotation, or 1.7 without.