Steel tension member / brace
A rolled shape, HSS, plate or threaded rod in axial tension, with its end connection: yielding on the gross section, rupture on the effective net area with the shear lag factor U computed by the case of AISC 360-22 Table D3.1, staggered holes, block shear and bearing at a bolted end, and the L/r recommendation. To AISC 360-22 Chapter D with B4.3b, J3.7, J3.11 and J4.3. Pin-connected members and eyebars (D5, D6) are in the steel column type, not here.
Inputs of the tension member #
- Member: a shape of the AISC Shapes Database v16.0 (W, S, M, HP, C, MC, WT, MT, ST, single and double angles, rectangular and round HSS, pipe), a plate (width and thickness) or a threaded rod (diameter). The steel grade (AISC Manual Tables 2-4, 2-5; ASTM F1554 for rods) and the fabricated length L.
- Loads: the axial loads by type, tension positive; the ASCE 7-22 combinations are formed, W and E both ways. A combination that puts the member in compression is flagged: design it as a column.
- End connection: bolted or welded; whether the force reaches every element of the section (Table D3.1 Case 1); which part is connected (W flanges or web, tee flange or stem, the angle leg); U computed or entered (your value and basis).
- Bolts: diameter (standard holes of Table J3.3), the number of bolt lines over the whole connection and the bolts per line, spacing and end distance. The net area takes each hole 1/16 in. wider (B4.3b), either across a straight section or over failure paths you enter with their Σ s²/4g. Whether hole deformation at service load is a design consideration (J3.11a: usually yes). Block shear: the planes, tension length and holes of one block, the number of blocks, and whether the tension stress is uniform (Ubs = 1) or not (0.5): your reading of the Commentary figures.
- Welds: longitudinal only (Case 4), longitudinal and transverse (Case 2), transverse only (Case 3), or for HSS a single slotted concentric gusset (Case 5) or two side gussets (Case 6); the weld lengths l1, l2 (l is their average), the weld size, the gusset thickness and the slot's clearance (1/16 in. in Design Examples D.4, D.5).
Auto-design varies the shape (lightest first within the given family), the plate thickness or the rod diameter. Loads, length, grade and the connection layout are kept.
Checks performed #
| Check | Basis |
|---|---|
| Tensile yielding, Fy Ag | 360-22 D2(a), Eq. D2-1 |
| Tensile rupture, Fu Ae, Ae = U An | 360-22 D2(b), Eq. D2-2, D3-1, B4.3b |
| Shear lag U by case, with the lower bound for open sections | Table D3.1 Cases 1 to 8, D3 |
| Block shear at the bolted end | J4.3, Eq. J4-5 |
| Bearing and tearout at the member's holes | J3.11a, Eqs. J3-6a to J3-6d |
| Longitudinal welds at least 4 times the weld size | Table D3.1 note [a] |
| Threaded rod: rupture on Fnt = 0.75 Fu, body yielding | J3.7, Table J3.2; D2 |
| L/r at most 300 (a recommendation, shown as advisory; not for rods) | D1 User Note |
x̄ is taken as the Commentary shows it (Figure C-D3.1): d/2 − Zx/A for a W connected by its flanges, Zy/A by its web, x̄ of the channel, ȳ of the tee, x̄ or ȳ of the angle by the connected leg. For a tee connected by its stem the same reasoning gives Zy/A, and Case 7 for a tee takes the parent's depth as twice the tee's (both to confirm against the code text).
Limitations #
- The bolts, welds and gusset plate are not designed here (bolt group, weld group and gusset types); neither are bolt spacing and edge distances (J3.3 to J3.6).
- Pins and eyebars (D5, D6), fatigue (Appendix 3) and tension with flexure (Chapter H) are in the steel column type.
- A failure path takes one thickness: a path through elements of different thickness is entered as an equivalent.
- A bolted HSS end has no Table D3.1 case: enter U.
- The 2022 HSS Cases 5 and 6 are read from the specification text, whose layer prints the exponents and the pairing of B and H poorly; Case 5 matches Design Examples D.4 and D.5, Case 6 is a hand check (to confirm against the code text).
Verification examples #
Verification status: 48 values compared in 10 examples (7 published, 3 hand calculations from the cited equations): 48 within tolerance, 0 recorded deviations. Code basis: the provisions it uses were read in the target edition.
AISC Design Examples v16.0 D.1 to D.6 and D.9 (yielding, rupture, U, An, L/r). Block shear, bearing, the threaded rod and Case 6 are hand calculations from the cited equations: the Examples assume the connection does not govern.