Lifting Lug / Padeye Pin-Hole Check
Checks an engineered lifting lug or padeye against four ASME BTH-1 pin-hole failure modes.
Example
You enter
- Applied load (kip) 20
- Plate thickness t (in) 1
- Hole diameter Dh (in) 1.06
- Pin diameter Dp (in) 1
- Hole-center to edge a (in) 2
- Plate width at hole w (in) 4
- Yield Fy (ksi) 36
- Ultimate Fu (ksi) 58
- Design factor Nd 2
You get
- Bearing (kip) 22.5
- Tearout (kip) 56.21
- Demand-to-capacity ratio 0.89
Checked against published worked examples from: ASME BTH-1 Section 3-3.3 (pin-connected plates).
Details, formula, and sources
ScopeBearing, tension through the pinhole, single-plane fracture beyond the hole, and double-plane shear tear-out (dishing is a separate check) -- and reports the governing capacity and DCR. These modes trade off through hole placement; a lug sized for gross tension alone can tear out at the pin.
Formula or tablebearing = 1.25 Fy Dp t / Nd; tension through the pinhole = Cr Fu 2 t beff / (1.20 Nd), beff = min(4t, be, 0.6 be (Fu/Fy) sqrt(Dh/be)), Cr = 1 - 0.275 sqrt(1 - Dp²/Dh²); single-plane fracture beyond the hole = Cr Fu / (1.20 Nd) [1.13 (a - Dh/2) + 0.92 be / (1 + be/Dh)] t; double-plane shear tear-out = 0.70 Fu Av / (1.20 Nd), Av = 2 t (a - Dh/2 + (Dp/2)(1 - cos φ)), φ = 55 Dp/Dh degrees; governing = min of the four; DCR = load / governing.
Source and editionThe ASME BTH-1 Section 3-3.3 pin-connected-plate (lifting lug / padeye) strength checks, by name.
Free accessASME BTH-1 is available through ASME; the pin-plate strength relations are established design checks. An estimate; the engineer of record governs.
What governsEstimate. Head rigger and manufacturer working-load-limit charts govern. Inspect every piece of hardware before the show.
API field namesapplied_load_kip, plate_thick_in, hole_dia_in, pin_dia_in, edge_dist_in, plate_width_in, fy_ksi, fu_ksi, design_factor, bearing_kip, tearout_kip, dcr
- Three checked modes bearing, tension through the pinhole, and double-plane shear tear-out; the minimum governs (dishing and cheek-plate welds are separate)ASME BTH-1 3-3.3
- Design factor Nd 2.00 (Design Category A, the default) or 3.00 (Category B); 1.67 is AISC's ASD factor, not BTH-1'sASME BTH-1 3-1.3