Cold-formed steel shear wall

A Type I cold-formed steel shear wall segment sheathed with wood structural panels or steel sheet: nominal unit shear from the sheathing and screw spacing, the aspect-ratio rules, the overturning forces on the chord studs and the hold-downs. AISI S400-20 (seismic) and AISI S240-20 (wind), chord studs by AISI S100-16, ASCE 7-22 load combinations, LRFD or ASD. The seismic provisions and tables were checked on 1 November 2026 against AISI S400-15 with Supplement S1-16, the edition on disk; S400-20 is taken as unchanged in them until it is available.

Inputs of the cold-formed steel shear wall #

• Wall: the segment length w and height h, and the stud spacing (the chord carries the gravity load of half a spacing).
• Sheathing and screws: 15/32 in. Structural 1 sheathing (4-ply), 7/16 in. OSB or 0.018 in. steel sheet, on one side or on both sides (same sheathing and screws: the strengths add), the edge screw spacing (6, 4, 3 or 2 in.; field 12 in.) and the stud and track thickness. The seismic value is read from the S400 table row for that thickness: wood structural panel rows apply to the listed thicknesses only (S400 Table E1.3-1 note 5), the steel sheet row to 33 mil or thicker; where two rows apply the larger value is used when the wall's aspect ratio is within the row's limit; the 68 mil rows require No. 10 screws (No. 8 otherwise). For any other assembly of the tables (other steel sheets) or a tested assembly, choose Entered and give the nominal unit shear for wind and for seismic (one side) and the maximum aspect ratio.
• Loads: the in-plane shears W and E at the top of the wall (strength level, E including ρ; both directions are checked) and the gravity line loads on the wall by load type. The dead load resists overturning with the factor of each combination (0.9D, 0.6D); every gravity load adds to the chord compression. Seismic amplification for chords and hold-downs: Ω0 = 3.0 is prefilled (ASCE 7-22 Table 12.2-1 for cold-formed steel light-frame walls sheathed with wood structural panels or steel sheet); the seismic part of the chord and hold-down forces is multiplied by it. SDS adds the vertical seismic effect Ev = 0.2SDS D (ASCE 7-22 12.4.2.2) to the seismic combinations: (1.2 + 0.2SDS)D and (0.9 − 0.2SDS)D in LRFD (2.3.6), (1.0 + 0.14SDS)D, (1.0 + 0.105SDS)D and (0.6 − 0.14SDS)D in ASD (2.4.5). It is 0 by default (Eh only, as in SDC B); a note says so while E is present.
• Chords and hold-downs: the chord stud (SSMA designation), the number of studs per chord, Fy, the bracing spacing of the chord (Ky Ly = Kt Lt; Kx Lx is the wall height), the distance from the wall end to the chord centroid e (d = w − 2e), and the hold-down's design strength (LRFD) or allowable strength (ASD) from its evaluation report for the stud thickness used.

Auto-design (editor toolbar) varies the sheathing, one or both faces, edge screw spacing, framing thickness and the chord studs (section and count). Objectives: lowest cost index (sheathing, screws, framing, chords). Every other input is kept; see Auto-design.

Checks performed #

The drawings (on screen, in the report and on the PDF / DXF drawing sheet) are the shear wall elevation (the wall with its chord studs at each end, the gravity loads by type, the in-plane shear V at the top, the hold-down location (T) and the compression chord (C), length and height) and the chord stud section. The sheathing, screw schedule, stud spacing, loads by type and the governing chord forces T and C with their combinations are in the sheet notes. The hold-down product, anchor rods, track anchorage, collectors, the sheathing panel layout and the arrangement of a built-up chord are not part of the calculation and are not drawn.

Limitations #

• Shear wall deflection and drift (S400 E1.4.1.4 / E2.4.1.4; Eq. E1.4.1.4-1 in S400-15) are not computed; check the story drift separately.
• Type I walls with blocked sheathing only; Type II (perforated) walls, unblocked sheathing, gypsum board, fiberboard and strap-braced walls are not covered.
• The seismic chord and hold-down forces use the amplified load (Ω0 × E). S400 E1.4.1.2 / E2.4.1.2 take the required strength from the wall's expected strength ΩE Vn (ΩE = 1.8, E1.3.3 / E2.3.3) but not more than the load with overstrength; the expected-strength value is not computed, so the module's force is never less than the required one (conservative).
• Built-up chords are taken as n individual studs, each braced at the entered spacing (no composite action). The chord studs are checked for axial load only (no out-of-plane wind bending of an exterior chord). Net-section fracture at the hold-down screws, the screws to the hold-down, the shear anchorage, the track and the collectors are not checked.
• Checked against AISI S400-15 with S1-16 (1 November 2026): the seismic unit shears of Tables E1.3-1 and E2.3-1 (U.S.), φ = 0.60 and Ω = 2.50, the summing of two sheathed sides (E1.3.1.1.2 / E2.3.1.1.3), the 2w/h rule to 4:1, the 24 in. minimum length and the capacity design of chords and hold-downs (E1.4.1.2). Corrected: the seismic values now follow the table rows by stud and track thickness (the module had used one row per sheathing taken from AISI S213-07, with 3 in. and 2 in. values the S400 table does not give for 33 mil framing, and 700 / 780 plf for every thickness: 7/16 in. OSB on 43 or 54 mil framing is 825 plf at 6 in.), and the 4:1 aspect ratio only for the rows that allow it.
• Still to verify: the same tables and factors in S400-20; the wind values and φ / Ω of AISI S240-20 Table B5.2.2.3-1 (not on disk; values from AISI S213-07); the equation number of the deflection equation in S400-20.

Verification examples #

Verification status: 27 values compared in 8 examples (6 published, 2 hand calculations from the cited equations): 27 within tolerance, 0 recorded deviations. Code basis: written from an older edition, with the differences noted. Not yet compared line by line with the target edition.

The seismic unit shears are checked against the published values of AISI S400-15 with S1-16 (Table E1.3-1, p. 19; Table E2.3-1, p. 30; Eq. E1.3.1.1-2 for 2 < h/w ≤ 4, p. 17; both faces E1.3.1.1.2, p. 18; φv = 0.60 / Ωv = 2.50, E1.3.2, p. 21) in S400-T1 to S400-T6. The arithmetic that follows (overturning, hold-down, chord studs) is checked by hand calculations in closed form (backend/tests/test_verify_cfs_shearwall.py). No free published worked example of a cold-formed steel shear wall design was found (the AISI D113 Shear Wall Design Guide is sold), so the chord and hold-down forces are compared with hand calculations only, and deflection is not computed by the module.

All values agree within 0.01 %.