Design of joint 8-9 (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, h₈ = 60 mm, a = 140 mm; the bending moments at the centre of the flange (the welded joint) are:

M_X9 = F_Y (L_c + Z₁) = 75000 Nmm,

M_Y9 = F_X (L_c + Z₁) + F_Z (X₁ + h₆/2 + a) = 550000 Nmm,

M_Z9 = F_Y (X₁ + h₆/2 + a) = 75000 Nmm.

Dimensional constraints: the lower column body 8 is welded to flange 9, with dimensions h₈ = 60 mm and thicknesses t₈ = 5 mm, g = 10 mm.

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

Design constraints: weldable materials for elements 8 and 9.

Materials and heat treatments

Elements 8 and 9 were designed in weldable S235 steel according to SR EN 10025-2 (STAS 500/2).

Material properties

Sizing

From the sizing relation obtained from the shear strength condition of the weld, with F_Xs = F_Z = 700 N, F_Ys = F_X = 1500 N, F_Zs = F_Y = 300 N; M_Xs = M_Z9 = 75000 Nmm, M_Ys = M_X9 = 75000 Nmm, M_Zs = M_Y9 = 550000 Nmm; h = h₈ = 60 mm; σ_at = 235/(2…3) = (78.33…117.5) MPa, σ_at = 100 MPa adopted; τ_afs = (0.6…0.7)σ_at = (60…70) MPa, τ_afs = 60 MPa adopted; the weld throat thickness is a^nec = 2.01 mm; a = 3 mm is adopted.

Constructive-technological shape