Design of joint 10-11 (welded joint) — example

Design data

External forces: F_X = 1500 N, F_Y = 300 N, F_Z = 700 N act at distances L_c = 70 mm; X₁ = 80 mm; Z₁ = 180 mm and h₆ = 60 mm, a = 140 mm, g = 10 mm; the bending moments at the centre of the flange (the welded joint) are:

M_X10 = F_Y (L_c + Z₁) = 75000 Nmm,

M_Y10 = F_X (L_c + Z₁) + F_Z (X₁ + h₆/2 + a + 2g) = 564000 Nmm,

M_Z10 = F_Y (X₁ + h₆/2 + a + 2g) = 81000 Nmm.

Dimensional constraints: flange 10 is welded to the central bar 11, with dimensions L_f = 120 mm, g = 10 mm, h₁₁ = 60 mm, t₁₁ = 5 mm.

Operating constraints: temperature T = (−30…40) °C; outdoor working environment with high humidity.

Design constraints: weldable materials for elements 10 and 11.

Materials and heat treatments

Elements 10 and 11 were designed in weldable S235 steel according to SR EN 10025-2 (STAS 500/2).

Material properties

Sizing

Calculation data

– loading: F_X = 1500 N, M_Y10 = 564000 Nmm;

– shape and dimensions: the weld bead is rectangular, with dimensions L_f = 120 mm and h₁₁ = 60 mm;

– materials: σ₀₂ = 235 MPa – the yield strength; c = 2…3 – the safety factor; σ_at = σ₀₂/c = (80…118) MPa – the allowable tensile stress; τ_afs = 0.65σ_at = 70 MPa – the allowable shear stress of the weld.

Sizing

From the sizing relation obtained from the shear strength condition of the weld, with F_X = 1500 N, M_Y10 = 564000 Nmm, h₁₁ = 60 mm and τ_afs = 70 MPa, the weld throat thickness is a^nec = 0.83 mm; a = 3 mm is adopted.

Constructive-technological shape