Methodology & References
Design load — total load at each lug = vessel weight × g × N_d. Single combined factor lumps dynamic, impact, and skew effects. Default N_d = 2.0 per ASME BTH-1 Class A; 3.0 for Class B.
Pin bearing — σ = P / (D_p · t) ≤ 1.25·F_y / N_d per BTH-1 §3-3.3.1.4.
Net-section tension — σ = P / [(W − D_h)·t] ≤ 0.45·F_y per BTH-1 §3-3.3.1.1.
Shear tear-out — τ = P / (2·a·t) ≤ 0.40·F_y per BTH-1 §3-3.3.1.2.
Double-plane shear — τ = P / [2t·√(R² − (D_p/2)²)] ≤ 0.40·F_y per BTH-1 §3-3.3.1.3.
Combined axial + bending at base — σ = P_v/(W·t) + 6·P_h·H/(t·W²) ≤ 0.66·F_y per AISC F1 / AS 4100 §8.
Weld combined action — closed rectangular line group L = 2(W+t); resultant σ_res = √[(τ_v + σ_b)² + τ_h²] ≤ φ·0.6·f_uw per AS 1554.1 §6.7.4.
Calculator implements widely-used limit-state checks for plate-type lifting and tailing lugs; an aid to qualified engineers. Does not assess local shell stress (refer WRC 107/297 or FEA), pad-to-shell weld design, lift-point clearance, or rigging hardware capacity. Final design and certification remain the responsibility of the responsible engineer per applicable Australian, ASME and project-specific codes.