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AISI S100-16(2020) w/S2-20United States

Cold-Formed Steel Beam

Beam reactions link to connected column calculations automatically - change a load once and every linked calculation updates. Design cold-formed steel sections to AISI S100-16(2020) using the Direct Strength Method for local, distortional, and global buckling; checks cover flexural strength, shear, web crippling at supports, and deflection. Assumes no holes in the cross-section; stiffeners are to be designed separately.

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What it calculates

Design cold-formed steel beam sections to AISI S100-16(2020) using the Direct Strength Method for local, distortional, and global buckling. Checks cover flexural strength, shear, web crippling, and deflection. Beam reactions link to connected column calculations so changes propagate automatically.

Code standards

  • AISI S100-16(2020) w/S2-20

How it calculates

The Cold-Formed Steel Beam calculator designs cold-formed steel sections to AISI S100-16(2020) using the Direct Strength Method (DSM). The FEA solver applies ASCE 7 LRFD factored load combinations and envelopes results to find the governing demands.

Flexural capacity (DSM)

Positive and negative moment capacities φMn are determined by DSM, which accounts for three buckling modes:

  • Global (lateral-torsional) buckling - governed by the effective unbraced lengths for top flange, bottom flange, and torsional restraint (Leff values entered by the user with effective length factor K for each axis).
  • Local buckling - critical local buckling load Mcrl is determined from the section geometry. The DSM local interaction equations give Mnl.
  • Distortional buckling - critical distortional buckling load Mcrd gives Mnd via the DSM distortional equations.

The nominal flexural capacity Mn = min(Mne, Mnl, Mnd) and the utilization check is Mu / φMn ≤ 1.0 where φ = 0.90.

Shear capacity

Shear capacity φVn is computed per AISI S100-16 Cl G2.1 based on web shear yielding and buckling. A combined bending-and-shear interaction check is applied where both demands are significant:

MV_int = (Mu/φMn)² + (Vu/φVn)² ≤ 1.0

Web crippling

Web crippling capacity φPn is checked at each support using AISI coefficients for the applicable loading condition (end one-flange, interior one-flange, nested/doubled). A combined bending-and-bearing interaction check is also applied for Cee and Zee sections.

Deflection

Three deflection limit states are checked against user-defined L/n thresholds: short-term (live/roof live service loads), long-term (creep-modified), and simplified DL+(LL or SL). Deflection utilization = δ / Δmax ≤ 1.0.

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Frequently asked questions

What design method and standard does this calculator follow?
AISI S100-16(2020) with Supplement 2 (S2-20), using the Direct Strength Method (DSM) for local and distortional buckling checks on cold-formed and light gauge steel sections. Load combinations follow ASCE 7/IBC LRFD provisions.
What are the key inputs?
Member designation (Cee, Zee, Hat, Track, or built-up section from the CFS section database, or custom dimensions), span length, support configuration, lateral bracing intervals for top flange, bottom flange, and torsional restraint (with effective length factor K for each), applied loads by type (D, L, Lr, S, R, W, Ev, Eh) as area intensities or point loads, and user-defined deflection limits (L/n ratios).
What checks does it perform?
Positive moment capacity φMn+, negative moment capacity φMn-, shear capacity φVn (AISI S100-16 Cl G2.1), bending-and-shear interaction, web crippling capacity φPn at supports, bending-and-bearing interaction (Cee/Zee sections), short-term deflection, long-term deflection, and simplified DL+(LL or SL) deflection. All checks are expressed as demand-to-capacity ratios.
Does it support back-to-back and boxed built-up sections?
Yes - the section type input allows Simple Beam (single section), Back-to-Back (two sections sharing the web), and Boxed Beam (two sections toe-to-toe). For built-up sections, a single-member DSM capacity is computed then multiplied by two.
What assumptions does the calculator make?
No holes in the cross-section. Stiffeners present are to be designed separately - their contribution to capacity is not included. The DSM implementation follows AISI S100-16 Appendix 1 for local and distortional buckling.
Does this calculator support load linking with column calculations?
Yes - beam support reactions link directly to connected column or footing calculations in the same project. When loads or geometry change in this beam, all linked calculations update automatically.

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