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 #

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 %.