Cold-Formed Steel DSM Verification
Benchmarking the shared DSM equations against the AISI DSM Design Guide (CF06-1, 2006). Country-specific routing is tested separately; independent AS/NZS and CSA end-to-end benchmarks remain a release-validation gap.
Methodology
All three CFS standards share a single DSM core engine. The 28 displayed rows use expected values from the AISI Direct Strength Method Design Guide (CF06-1, June 2006), with results shown in metric. Country-specific φ factors, clause mappings, and wrapper routing are covered by automated regression tests, including additional Bentley STAAD.Pro checks that are not displayed in this table.
Page references are the page numbers printed in CF06-1; in the local PDF they are offset by 12 PDF pages. Source inputs are retained in their published US customary units before results are converted for display.
These benchmarks verify the shared DSM numerical core; they do not independently validate complete AS/NZS 4600 or CSA S136 member workflows. Independent worked examples for those two national paths remain required before unrestricted commercial release. Web crippling is covered by automated formula-level hand calculations. Manual-warning and OUT_OF_SCOPE paths documented on the CFS engine page remain outside the benchmark set.
Signed minor-axis member LTB is populated only for 769 geometry-audited bundled Cee and lipped-Z sections. The Appendix 2 principal-axis equation is benchmarked against HH7121's independent mesh-converged finite-strip curve to within 1.5%; catalog geometry must also match stored area and principal inertias within 5% and J within 10%. Deferred families and failed records omit this member capacity and dependent biaxial member interactions rather than inherit a nearby section's curve. This documented product-scope omission does not set the overall result to OUT_OF_SCOPE.
- DSM Bending: Examples 8.1-1 (lipped Cee), 8.3-1 (unlipped track), 8.4-1 (modified track), and 8.5-1 (Z-section). All three buckling modes: global (LTB), local, and distortional.
- DSM Compression: Examples 8.1-4 (fully braced), 8.1-5 (global buckling at 6.1m), 8.3-3 (unlipped track), and 8.4-2 (modified track). Inelastic and elastic global regimes.
- Effective Ieff: Ieff/Ig reduction at service demand from Example 8.1-3 (p.83).
- LTB with Cb: Example 8.1-2 verifies Cb=1.67 pushes Mcre/My above 2.78 → stocky regime (Mne=My).
- N+M interaction comparator: Example 8.1-6 checks the legacy DSM Design Guide C5.2.2-1 member-stability and C5.2.2-2 section arithmetic. It is comparator evidence only: it does not validate current AISI/CSA H1.2 or certify Chapter C analysis compliance, and it is not an independent AS/NZS worked example.
Where textbook values differ from engine output by more than 0.5%, the deviation is explained, typically from integer rounding of intermediate kip-in values vs full-precision computation.
Verification Results
Demand rows compare the engine to a published number. Capacity-policy rows are labelled as a split, not scored as a percent fail.
| ID | Description | Section | Expected | Result | Diff % |
|---|---|---|---|---|---|
| CFS-01 | Bending, fully braced Cee: Mbe = My = 14.3 kN·m (no LTB reduction) AISI DSM Design Guide CF06-1, §8.1-1 (p.80) | 9CS2.5x059 (Fy=379 MPa) | 14.3 kN·m | 14.3 kN·m | 0.00% |
| CFS-02 | Local buckling Mbl: λl = 1.22, Mbl = 10.6 kN·m AISI DSM Design Guide CF06-1, §8.1-1 (p.80) | 9CS2.5x059 (Fy=379 MPa) | 10.6 kN·m | 10.6 kN·m | 0.13% |
| CFS-03 | Distortional buckling Mbd: λd = 1.08, Mbd = 10.5 kN·m AISI DSM Design Guide CF06-1, §8.1-1 (p.81) | 9CS2.5x059 (Fy=379 MPa) | 10.5 kN·m | 10.5 kN·m | 0.16% |
| CFS-04 | Governing Mn = min(Mbe, Mbl, Mbd) = 10.5 kN·m [Distortional] AISI DSM Design Guide CF06-1, §8.1-1 (p.81) | 9CS2.5x059 (Fy=379 MPa) | 10.5 kN·m | 10.5 kN·m | 0.16% |
| CFS-05 | Compression, fully braced Cee: Nce = Ny = 215.4 kN AISI DSM Design Guide CF06-1, §8.1-4 (p.85) | 9CS2.5x059 (Fy=379 MPa) | 215.4 kN | 215.3 kN | 0.04% |
| CFS-06 | Local buckling Ncl: λl = 2.89, Ncl = 86.3 kN AISI DSM Design Guide CF06-1, §8.1-4 (p.85) | 9CS2.5x059 (Fy=379 MPa) | 86.3 kN | 86.2 kN | 0.08% |
| CFS-07 | Distortional buckling Ncd: λd = 1.92, Ncd = 87.2 kN AISI DSM Design Guide CF06-1, §8.1-4 (p.85) | 9CS2.5x059 (Fy=379 MPa) | 87.2 kN | 87.1 kN | 0.11% |
| CFS-08 | Governing Nc = min(Nce, Ncl, Ncd) = 86.3 kN [Local] AISI DSM Design Guide CF06-1, §8.1-4 (p.85) | 9CS2.5x059 (Fy=379 MPa) | 86.3 kN | 86.2 kN | 0.08% |
| CFS-09 | Global buckling 6.1m column: λc = 0.96, Nce = 145.9 kN AISI DSM Design Guide CF06-1, §8.1-5 (p.86) | 9CS2.5x059 (Fy=379 MPa) | 145.9 kN | 145.9 kN | 0.01% |
| CFS-10 | Local + global interaction: Ncl = 67.6 kN AISI DSM Design Guide CF06-1, §8.1-5 (p.86) | 9CS2.5x059 (Fy=379 MPa) | 67.6 kN | 67.5 kN | 0.18% |
| CFS-11 | φcNc = 0.85 × 67.6 = 57.4 kN (global + local governs) AISI DSM Design Guide CF06-1, §8.1-5 (p.87) | 9CS2.5x059 (Fy=379 MPa) | 57.4 kN | 57.4 kN | 0.10% |
| CFS-12 | Bending, unlipped track: Mbe = My = 2.51 kN·m AISI DSM Design Guide CF06-1, §8.3-1 (p.93) | 550T125-54 (Fy=228 MPa) | 2.51 kN·m | 2.51 kN·m | 0.00% |
| CFS-13 | Distortional Mbd = 2.17 kN·m (governs for unlipped track) AISI DSM Design Guide CF06-1, §8.3-1 (p.94) | 550T125-54 (Fy=228 MPa) | 2.15 kN·m | 2.17 kN·m | 1.21% |
| Textbook rounds to integer kip-in. Engine keeps full precision. | |||||
| CFS-14 | Bending, Z-section: Mbl = 9.8 kN·m (local) AISI DSM Design Guide CF06-1, §8.5-1 (p.104) | 8ZS2.25x059 (Fy=379 MPa) | 9.8 kN·m | 9.8 kN·m | 0.61% |
| CFS-15 | Distortional Mbd = 8.6 kN·m (governs over local) AISI DSM Design Guide CF06-1, §8.5-1 (p.104) | 8ZS2.25x059 (Fy=379 MPa) | 8.6 kN·m | 8.6 kN·m | 0.28% |
| CFS-16 | φbMn = 0.90 × 8.6 = 7.7 kN·m AISI DSM Design Guide CF06-1, §8.5-1 (p.104) | 8ZS2.25x059 (Fy=379 MPa) | 7.8 kN·m | 7.7 kN·m | 0.59% |
| The guide prints Mn = 76 kip-in; the engine retains the unrounded value, 76.21 kip-in. | |||||
| CFS-17 | Bending, modified track: no local reduction (λl < 0.776) AISI DSM Design Guide CF06-1, §8.4-1 (p.101) | Mod. 550T125-54 (Fy=228 MPa) | 2.55 kN·m | 2.55 kN·m | 0.00% |
| CFS-18 | Compression, modified track: Pn = 35.5 kN [Distortional] AISI DSM Design Guide CF06-1, §8.4-2 (p.102) | Mod. 550T125-54 (Fy=228 MPa) | 35.5 kN | 35.6 kN | 0.30% |
| Textbook reports Pn=7.98 kip. Engine uses full-precision DSM intermediates. | |||||
| CFS-19 | Compression, unlipped track: Ncl = 40.0 kN (local) AISI DSM Design Guide CF06-1, §8.3-3 (p.97) | 550T125-54 (Fy=228 MPa) | 40.0 kN | 40.0 kN | 0.05% |
| CFS-20 | Distortional Ncd = 31.6 kN (governs for unlipped track) AISI DSM Design Guide CF06-1, §8.3-3 (p.97) | 550T125-54 (Fy=228 MPa) | 31.6 kN | 31.4 kN | 0.43% |
| CFS-21 | Track with global buckling: Nce = 23.8 kN (inelastic) AISI DSM Design Guide CF06-1, §8.3-4 (p.98) | 550T125-54 (Fy=228 MPa) | 23.8 kN | 23.7 kN | 0.15% |
| CFS-22 | Track global+local: Pn = 20.5 kN, φcPn = 16.5 kN AISI DSM Design Guide CF06-1, §8.3-4 (p.98) | 550T125-54 (Fy=228 MPa) | 16.5 kN | 16.3 kN | 1.00% |
| Textbook rounds Pn=4.6→4.6 kip. Engine keeps full precision. | |||||
| CFS-23 | Z-section compression, fully braced: Pn = 84.5 kN [Distortional] AISI DSM Design Guide CF06-1, §8.5-3 (p.106) | 8ZS2.25x059 (Fy=379 MPa) | 84.5 kN | 84.3 kN | 0.27% |
| CFS-24 | Z-section with global buckling: Pn = 55.6 kN [Local + global] AISI DSM Design Guide CF06-1, §8.5-4a (pp.107-108) | 8ZS2.25x059 (Fy=379 MPa) | 55.6 kN | 55.3 kN | 0.56% |
| CFS-25 | Effective Ieff: Ieff/Ig = 0.96 at service moment M = 55.88 kip-in (6.31 kN·m) AISI DSM Design Guide CF06-1, §8.1-3 (p.83) | 9CS2.5x059 (Fy=379 MPa) | 0.96 | 0.965 | 0.52% |
| Engine exact value is 0.965 from full-precision DSM intermediates. | |||||
| CFS-26 | Bending with LTB: Mcre/My=2.89 (Cb=1.67) → Mne=My (stocky) AISI DSM Design Guide CF06-1, §8.1-2 (p.82) | 9CS2.5x059 (Fy=379 MPa) | 14.3 kN·m | 14.3 kN·m | 0.00% |
| CFS-27 | N+M interaction Eq C5.2.2-1: Pu/φNc + CmMu/(φMb·α) ≈ 1.0 AISI DSM Design Guide CF06-1, §8.1-6 (p.88) | 9CS2.5x059 (20ft beam-column) | 1.00 | 1.006 | 0.59% |
| Textbook says "= 1". Engine: 1.006 from exact intermediates. | |||||
| CFS-28 | N+M section Eq C5.2.2-2: Pu/φPno + Mu/φMn = 0.89 AISI DSM Design Guide CF06-1, §8.1-6 (p.88) | 9CS2.5x059 (20ft beam-column) | 0.89 | 0.89 | 0.01% |
Disclaimer: This verification page is provided for informative purposes only and does not constitute a guarantee of accuracy for all possible configurations. While we use automated verification checks to help find defects, no software is entirely free of defects. Engineers must exercise independent professional judgement and verify results through their own checks before relying on any output for design or construction decisions. AutoCalcs accepts no liability for errors, omissions, or any consequences arising from the use of this software.