Web holes in cold-formed members
A C-section checked at the section of a web hole, punched, unpunched or reinforced, under the forces you enter there. To AISI S100-16 (with S2-20) F3.1.2, F4.2, G3, G6 and Appendix 1 1.1.1 and 1.1.3.
Inputs of the web hole check #
- Member: an SSMA designation or custom dimensions, and Fy.
- Web hole: punched (circular, or noncircular with depth dh and length Lh), none (the unpunched member, to compare), or reinforced. The hole spacing along the member enters the G3 / G6 clear distance and the compression limits.
- Reinforced: S100-16 has no strength for a reinforced hole. The usual detail is a patch of the same or thicker steel lapped past the hole and screwed around it. Once you have designed it and confirm it, the member is checked as unpunched. The patch and its screws are your design.
- Forces at the hole: axial compression, moment and shear by load type, from your analysis of the member; the ASCE 7-22 combinations follow.
- Bracing: Kx Lx, Ky Ly, Kt Lt, a braced compression flange, Cb, distortional buckling with Lm and kφ.
- Bearing near the hole: the case (end or interior one-flange), the bearing length N, the flange fastening, the hole's distance from the edge of bearing x, and the reaction by load type.
Auto-design varies the section (lightest first). The hole, forces and bracing are kept.
Checks performed #
| Check | Basis |
|---|---|
| Hole limits (depth, length, dh/h, h/t, 9/16 in.) | S100 G3, G6, Appendix 1 1.1.3 |
| Clear distance between holes at least 18 in. | S100 G3(d), G6(d) |
| Compression hole limits | S100 Appendix 1 1.1.1 |
| Flexure at the hole | S100 F2 (gross), F3.1.2, Appendix 1 1.1.3(a) |
| Distortional buckling with the hole | S100 F4.2, Appendix 2 2.3.4.3 |
| Shear at the hole, c/t at least 5 | S100 G2, G3 |
| Bending and shear | S100 H2 |
| Compression at the hole | S100 E2, E3, Appendix 1 1.1.1 |
| Compression and bending | S100 H1.2 with B1 (C1.2.1.1) |
| Web crippling next to the hole | S100 G5, G6 (Eqs. G6-1, G6-2) |
Limitations #
- The hole is taken centred in the web.
- The forces at the hole are yours; this type does not analyse the member.
- A hole within the bearing length needs a bearing stiffener (G6): not covered.
- A reinforced hole is checked unpunched on your confirmation; the patch is not designed (CFSEI technical note on web hole reinforcement, not on disk, to confirm against its text).
- The E3.1.2 exemption for small circular holes is not applied (conservative).
Verification examples #
Verification status: 27 values compared in 15 examples (13 published, 2 hand calculations from the cited equations): 27 within tolerance, 0 recorded deviations. Code basis: not yet recorded for this module.
Published values: the SSMA Product Technical Guide (2022), pp. 10-12 (Vanet at the 1-1/2 × 4-1/2 in. punchout for six sections; Mal, Mad and Vag of five unpunched sections) and p. 59 (web crippling). Hand calculations: a circular hole by G3 and a hole near an end bearing by G6. No published example of a punched member in compression or of F4.2 is on disk (AISI D100).