Designing a tension member end connection

The Tension member end type (Wizard group Truss & bracing, mark prefix TM) checks the end of a member in axial tension where it is bolted or welded to a gusset (or splice) plate: the member itself by AISC 360-22 Chapter D, and the connection by Chapter J. It covers the member shapes of the AISC Design Examples, Chapter D:

Tension member inputs #

• Loads: service dead and live tension (LRFD 1.2D + 1.6L or 1.4D, ASD D + L), a required strength, ASCE 7 combinations or load cases.
• Member: shape, section (the list follows the shape), material, the connected leg of an angle, and the member length. The length is used only for the recommended slenderness limit L/r ≤ 300 (enter 0 to skip it).
• Bolt pattern (bolted): bolt lines and bolts per line, pitch s, gage g (W and WT: the gage across the web; four lines per flange use the outer line gage), the first line from the angle heel, the plate side edge distance, the middle gage of a plate with four or more lines, the stagger (alternate lines offset, or the inner lines offset as in Example D.9) with its offset, and the end distances of the member and of the gusset.
• Welds (welded, and always for HSS): fillet size, weld length of each line, electrode; for HSS the slotted walls and the slot clearance beyond the gusset thickness (1/16 in. in Examples D.4 and D.5).
• Gusset: thickness (for a double angle this is also the separation), material, and the gusset width at the connection when it limits the Whitmore section (0 = wide gusset). A W-shape has one plate per flange.

Tension member checks #

• Tensile yielding Pn = Fy Ag (D2a, φ = 0.90, Ω = 1.67).
• Tensile rupture Pn = Fu Ae, Ae = An U (D2b, D3, φ = 0.75, Ω = 2.00). The net area deducts the holes (dh + 1/16 in.) or, for HSS, the two slots. With staggered bolts every failure path through one hole per line is listed with its Σ s²/4g term and the least net width governs. The shear-lag factor U is the largest applicable value of Table D3.1: Case 1 (bolted plate), Case 2 (1 − x̄/l), Case 4 (longitudinal welds only), Case 7 (W and WT flanges, three or more bolts per line), Case 8 (angles), the slotted-HSS cases, and never less than the connected area over Ag for open sections.
• Block shear of the member and of the gusset (J4.3).
• Bolts: shear, bearing and tearout per bolt on the member and on the gusset, the group as the sum of the per-bolt least values; slip resistance when slip-critical; spacing, edge distances and maximum limits.
• Welds: fillet strength with kds = 1.0 and the long-weld factor β, shear rupture of the member and of the gusset along the welds, minimum and maximum size, minimum length.
• Gusset: Whitmore-section yielding and rupture.
• Slenderness: L/r ≤ 300 as a recommendation (Spec. D1 User Note).
• Fatigue (Appendix 3): with Cyclic loading (fatigue) ticked, the member and the gusset (Whitmore section) at the bolt holes (Table A-3.1 Case 2.1 slip-critical on the gross section, 2.2 pretensioned on the net section, or Case 1.5 for snug-tight joints), or, welded, the member and the gusset at the ends of the longitudinal welds (Case 4.1, E for t ≤ 1/2 in., E′ above) and the fillets (Case 8.2, F). Cycle count and range as for the single plate; see Fatigue (Appendix 3).

Tension member drawings #

The elevation shows the member on its gusset with the member broken off past the connection: bolts in end view (W-shapes from the side, the bolts through each flange and plate in side view), or the welds seen face-on with the weld symbol, and the bolt pitch, end distances and gages dimensioned (staggered bolts at their offsets). Section A-A cuts the member at the connection: the member cross-section on the gusset, the bolts through the grip or the fillet welds in true cross-section (slotted HSS: the gusset through both walls with the four welds).

Tension member verification #

Design Examples v16.0 D.1 to D.6 and D.9 are reproduced row by row (required strength, U and each Table D3.1 case, An, Ae, the available strengths, L/r, the D.9 net widths of every path); see the Verification page. The examples assume that the connection does not govern, so their published conclusion is compared with the member limit states; the connection checks are reported alongside. Pin-connected members and eyebars (D.7, D.8) are a separate type.

Tension member limits #

• The holes are deducted only in the connected elements; W and WT bolt lines are straight (no stagger).
• Block shear of a welded open section is not checked for the member (the base-metal shear rupture along the welds is); the stagger term is not used in the block-shear tension planes.
• The gusset is checked at its Whitmore section only; its connection to the support is a separate design.
• The 2L separation is the gusset thickness; the least radius of gyration of a 2L comes from Manual Table 1-15 when the separation is listed, else from the parallel-axis rule.