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Cold-Formed Steel Beam and Column Design

Independently of panel studs, a bond beam (beam) or tie column (column) in the model can be designed with a cold-formed steel section. The calculation is carried out through the effective width method (EWM) with the finite element envelope forces of the member (M3, V2, N; additionally M2 for columns) — the cold-formed steel counterpart of the steel beam and column workflow. For panel design, see the article Cold-Formed Steel Panel and Stud Design.

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Which editions? Cold-formed steel calculations are available in the StatiCAD Ultimate edition.

1. Assigning a section​

  1. In the Bond Beam (Tie Column) Properties window, select the “Cold-Formed Steel” option in the Member Type box (next to the timber and steel options).
  2. Open the Prefabricated Profile window for the section and select the C, Z, U, C+, Sigma or Sigma+ category under Cold Formed. The 527 profiles in the predefined tables are listed in the form “CC C200x80x16x2”, “ZZ Z200x60x15x2”, “UU U200x94x4”, “CPLUS C+200-89x25x15x4”, “SIGMA S200-50x67x16x2”, “SIGMAPLUS S+200-55x95x25x15x4”.
  3. Select the profile and click Assign; the section drawing (actual outline), the gross properties (catalogue A, Ix, Iy) and the torsional properties come automatically. A steel grade (e.g. S235, S355) is assigned as the material; Fy and E are read from this material.
  4. Run the analysis; the results appear in the analysis warning list and in the report.

2. Load combinations​

The demands are taken from the HCBTİE 4.3.1 combinations in addition to the program’s combinations — LRFD: 1.4G; 1.2G + 1.6Q + 0.5S; 1.2G + 1.6S + 1.0Q; if wind is present, 1.2G + 1.0Q + 0.5S + 1.6W and 0.9G + 1.6W; ASD: the corresponding ASCE 7 combinations. In this way the vertical combination factors in the project (default 1.0G + 1.0Q) do not fall short for cold-formed steel members. The report gives the name of the governing combination; the marking “[1.2G+1.0Q]” or “[GKT]” shows that the factors of the program combination have been converted according to the method (GKT: ASD).

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There is no wind load case in the TBDY combination list: for wind to be included in beam and column design, defined load cases and combinations must be selected (otherwise a warning is given). Beam deflection is calculated from the unfactored service combinations (G + Q, G + S). The design method (LRFD/ASD) comes from the same project setting as for the panel studs.

3. Checks​

MemberDemands (analysis envelope)Buckling lengthsChecks
BeamM3, V2, NLx = span; unbraced length by moment sign: Lb+ = member length or user Le (if the top flange is connected to the sheathing, there is no lateral–torsional buckling under positive moment), Lb− = bracing interval of the bottom flange (Lb+ if there is no input); Cb from the moment diagram (1 for a cantilever and when Lb < L)Signed M+/Md+ and M−/Md−, V/Vd, P/Pd + M/Md (Eq. 4.8.4), combined bending + shear (Eq. 4.8.5/4.8.6, Mdlo in the denominator), web crippling at the support (4.8.3), 7.4 stiffener requirement, deflection L/K and live-load-only L/250 (Table 7.1), vibration (7.5)
ColumnN, M3, M2, V2KLx = KLy = storey height (K = 1) or user inputN/Pd, P/Pd + Mx/Md,x + My/Md,y (Eq. 4.8.4), V/Vd, KL/r > 200 warning; for a column in tension, T/Td (Eq. 4.8.1/4.8.2)
  • The bending strength is the smallest of the global (lateral–torsional), local and distortional buckling rows; the compressive strength is determined in the same way.
  • For columns, the weak-axis bending capacity is calculated separately for the two directions from the effective section.
  • The adequacy of the edge stiffener (lip) is checked according to HCBTİE 4.9.3; if there is a reduction, it is written in the footnote of the report.
  • Sections that do not satisfy the HCBTİE Chapter 3 cross-section conditions (e.g. the lip is ignored in sections with a lip/flange ratio < 0.20) are indicated in the footnote of the report.
  • For the inputs specific to floor joists (sheathing connection, bottom flange bracing interval, support type, bearing length, stiffener, bridging) and the details of the checks, see the article Cold-Formed Steel Floor: Floor Joists and Diaphragm.
  • The Z section is calculated as a purlin/beam bending about the axis perpendicular to the web; in the U section, since there is no lip, the flanges are taken as unstiffened elements and no distortional row occurs; in C+ and Sigma+ sections the return lip at the end of the lip is taken into account as part of the edge stiffener.

4. Rotational restraint of the sheathing​

For beams and columns too, the rotational restraint (kφ) that the sheathing provides to the flange can be taken into account: in the member properties (Timber2 tab for a beam, Timber tab for a column), the sheathing type, member spacing, board bending stiffness, screw spacing and, if necessary, the user kφ value are entered in the “Cold-Formed Steel: sheathing rotational restraint” box.

  • The entered sheathing is assumed to be present on both flanges; leave “Undefined” for members with only one flange sheathed.
  • For edge members where the board is on only one side of the member (e.g. an edge slab beam), enter half of the board bending stiffness.
  • Conditions: screw spacing ≤ 305 mm and member spacing ≤ 625 mm; otherwise kφ = 0 is taken and the reason is written in the report.

5. Reports​

If the project contains a cold-formed steel beam or column, the Cold-Formed Steel Beam Design (EWM) and Cold-Formed Steel Column Design (EWM) pages appear in the Cold-Formed Steel Member Reports group: member name and section, geometry (L, Lb / KL, slenderness, A, I), method and material, demands and governing combinations, bending (global / local / distortional → Md; positive and negative moment separately for beams), shear, axial + bending interaction, deflection for beams, web crippling, web stiffener and vibration rows, compression rows for columns and a note on assumptions.

6. Predefined cold-formed steel profile library​

The profiles are read from the HafifCelikProfil.txt file in the installation folder. The table contains the 527 predefined cold-formed steel sections: C (89), Z (90), U (88), C+ (87), Sigma (90), Sigma+ (83); height 100–400 mm, wall thickness 1.0–4.0 mm.

Each row contains the type code (1 = C, 2 = Z, 3 = U, 5 = Sigma, 8 = C+, 9 = Sigma+), the full geometry (H, A, B, C1, C2, D return lip, E, F, G, T, R) and the catalogue section properties (weight, A, Ix, Wx, ix, Iy, Wy, iy, ex, ey). Only C, C+, Sigma and Sigma+ sections are offered in the panel stud list. In design, the gross A, Ix, Iy are taken from the catalogue columns; the geometry columns are used in the effective width, torsion and distortional buckling calculations.

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Adding your own profiles: The file is in simple text format; lines beginning with # are comments. You can add your own profiles with the same column layout (geometry in mm, section properties in cm units, decimal separator is a point). If the catalogue columns are left empty or 0, the properties are calculated from the geometry (sharp-corner model, a few percent higher).

# Tip|Ad|H|A|B|C1|C2|D|E|F|G|T|R|Agirlik_kgm|Alan_cm2|Ix_cm4|Wx_cm3|ix_cm|Iy_cm4|Wy_cm3|iy_cm|ex_cm|ey_cm
1|C200x80x16x2|200|80|80|16|16|0|0|0|0|2|3|5.9|7.51|471.93|47.19|7.91|60.29|10.51|2.83|2.26|0
5|S200-50x67x16x2|200|67|67|16|16|0|50|15|25|2|3|5.89|7.5|430.94|43.09|7.55|32.56|7.46|2.08|2.34|0

7. Scope and assumptions​

  • Only the sections in the predefined profile table (HafifCelikProfil.txt) are calculated; if a section that is not in the library is assigned, the calculation is marked inadequate with the note “kütüphanede yok” (not in the library).
  • The beam calculation is based on the assumption that the load passes through the shear centre or that torsion is restrained by the connections (HCBTİE Chapter 5). In C, U and C+ beams, if the two flanges are not effectively connected to the sheathing, additional torsional bracing must be provided.
  • The Z section is calculated only for bending about the axis perpendicular to the web; bending about the principal axis and biaxial behaviour without lateral restraint are not modelled.
  • For tension in columns, the net area is taken equal to the gross area; screw and bolt holes and the connection strength must be checked separately.
  • The artificial (composite) axial force produced together by the beam axis offset and the rigid diaphragm is subtracted from the axial force in cold-formed steel beam design (see Cold-Formed Steel Floor: Floor Joists and Diaphragm).

8. Frequently asked questions​

I get the warning “… hafif çelik kiriş/kolon hesabı yapılamadı: kesit kütüphanede yok” (… cold-formed steel beam/column calculation could not be performed: section not in the library). A section other than the predefined profile table has been assigned to the member. Select a section from the C, Z, U, C+, Sigma or Sigma+ category under Prefabricated Profile → Cold Formed.

I get the warning “… hafif çelik kiriş yetersiz (M/Md=… V/Vd=… sehim=…)” (… cold-formed steel beam inadequate (M/Md=… V/Vd=… deflection=…)). Increase the section or review the lateral bracing (Le) inputs. If the top flange of a floor joist is continuously connected to the sheathing, tick this in the Cold-Formed Steel tab; under positive moment lateral–torsional buckling is eliminated.

In the U profile report the distortional rows say “yok” (none). The distortional buckling row is not applicable to a U section without lips; these rows are for flanges with edge stiffeners.

A “Çekme” (Tension) row appears for the column. The column is in tension in at least one combination. The tensile strength is calculated with the assumption net area = gross area; holes and connection strength must be checked separately.