Cold-formed steel track anchorage
The bottom (or top) track of a wall fastened to concrete or steel: uplift and shear along and across the track per foot, the fastener at each location and the track sheet around it. To AISI S100-16 J3.3, J4, J5 and J7, with the loads combined by ASCE 7-22 2.3.1 or 2.4.1.
The track type (cfs_track) designs the stud-to-track connection under the studs' out-of-plane reaction. This type adds what that one does not: uplift, in-plane shear, the S100 power-actuated fastener equations (J5 and J7.2), pull-over of the track and the combined tension and shear check.
Inputs of the track anchorage #
- Track: thickness (mils), Fy, Fu (ASTM A1003: 45 ksi for 33 ksi steel, 65 ksi for 50 ksi) and the web width; the fastener sits on its centreline.
- Loads per foot of track, nominal, by load type: uplift (dead load on the track negative), shear along and across the track. For a Type II shear wall, AISI S240-20 B5.2.4.3 asks the bottom track between the wall ends to be anchored for an uplift equal to the unit shear v plus any roof uplift: enter it as an uplift row.
- Fasteners: power-actuated fasteners (PAFs) into concrete or steel, screws into steel, or anchor bolts or screw anchors into concrete; the spacing and the number at each location.
- PAFs: shank diameter, head or washer diameter (at most 0.6 in. counts, J5), the pull-over factor αw of J5.2.3, the hardness (HRC 52 or more gives Fuh = 260 ksi), and the pull-out strength from the product's evaluation report (S100 gives no equation: J5.2.2, J7.1.2).
- Concrete: f′c, normal weight or not, thickness, embedment hET and edge distance, which decide whether S100 J7.2.2 applies; otherwise the PAF shear strength from the report.
- Steel support: thickness t2, Fy2, Fu2, and the bearing factor αb of J5.3.2.
- Anchors: diameter, washer, and the anchor's tension and shear strengths from ACI 318-19 Chapter 17 (the anchor types of this program) or its report.
Auto-design varies the fastener spacing (widest first), the number at a location and the track thickness. The fastener kind and size, the support and the loads are kept.
Checks performed #
| Check | Basis |
|---|---|
| PAF in concrete: pull-out in shear, Pnos = 1,450 lb (φ 0.50, Ω 3.25), with conditions (a) to (e) | S100 J7.2.2, Table J7.2.1-1 |
| PAF tension strength Pntp, shear strength Pnvp | S100 J5.2.1, J5.3.1 |
| PAF pull-out in tension | Evaluation report (S100 J5.2.2, J7.1.2) |
| Pull-over of the track | S100 J5.2.3 (PAFs), J4.4.2 (screws); J7.1.2 for anchors with the same form (to confirm against the code text) |
| PAF in steel: bearing and tilting, pull-out in shear | S100 J5.3.2, J5.3.3 |
| Track bearing at a PAF in concrete | S100 J7.1.3 with the Eq. J5.3.2-1 form (to confirm against the code text) |
| Screws: sheet shear, screw shear, pull-out, screw tension | S100 J4.3.1, J4.3.2, J4.4.1, J4.4.3 |
| Track bearing at an anchor bolt | S100 J3.3.1 (mf = 0.75: no washer under both head and nut) |
| Anchor tension and shear | ACI 318-19 Ch. 17 or the report (entered) |
| Spacing and edge distance | S100 Tables J5.1-1, J7.2.1-1; J4.1, J4.2 |
| Combined tension and shear | S100 J5.4, Commentary Eq. C-J5.4-1 with n = 1 (linear) |
Limitations #
- The concrete's own capacity (breakout, pryout, splitting) is in the strengths you enter; this type does not apply ACI 318 Chapter 17.
- The track's bending between fasteners under uplift, the studs, the stud-to-track connection and hold-downs are not designed.
- Combined tension and shear uses the linear form of Commentary Eq. C-J5.4-1 for every fastener kind; S100 J5.4 only asks for the interaction to be considered.
- The pull-over of the track at an anchor washer and the track bearing at a PAF in concrete use S100 equations written for steel-to-steel connections, a rational reading (to confirm against the code text).
Verification examples #
Verification status: 16 values compared in 4 examples (1 published, 3 hand calculations from the cited equations): 16 within tolerance, 0 recorded deviations. Thin: only 1 published example. Code basis: not yet recorded for this module.
The J7.2.2 shear strength (1,450 lb with φ 0.50 and Ω 3.25) is the value printed in AISI S100-16. No published worked example of a track anchorage is in the free library; the other values are hand calculations of the cited S100 equations.