Calculating Plate Joins with Double-Sided Butt Welds

Butt weld loaded with normal stress

Normal stress

where:

	F z	normal force [N, lb].
	A	throat area of the weld [mm 2 , in 2 ].

Comparative stress

where:

	σ 1	normal stress [MPa, psi]
	α 1	conversion factor of the weld joint [-]

Butt weld loaded with bending moment

Normal stress

where:

	u	constant
		- for calculation in metric units u = 1000
		- for calculation in English units u = 12
	M	bending moment [Nm, lb ft]
	W	section modulus of throat area of the weld [mm 3 , in 3 ]

Comparative stress

where:

	σ 2	normal stress [MPa, psi]
	α 1	conversion factor of the weld joint [-]

Butt weld loaded with bending force

Normal stress

where:

	F y	bending force [N, lb]
	e	force arm [mm, in]
	W	section modulus of throat area of the weld [mm 3 , in 3 ]

Shear stress

where:

	F z	axial force [N, lb].
	A	throat area of the weld [mm 2 , in 2 ].

Resultant reduced stress

where:

	σ 3	normal stress [MPa, psi]
	τ	shear stress [MPa, psi]

Comparative stress

where:

	σ 3	normal stress [MPa, psi]
	τ	shear stress [MPa, psi]
	α 1 , α 2	conversion factors of weld joint [-]

Butt weld loaded with combined loading

Total normal stress

σ = σ ₁ + σ ₂ [MPa, psi]

where:

σ 1 , σ 2

normal stress [MPa, psi]

Comparative stress

where:

	σ 1 , σ 2	normal stress [MPa, psi]
	α 1	conversion factor of the weld joint [-]

Butt weld loaded with combined loading

Resultant reduced stress

where:

	σ 1 , σ 3	normal stress [MPa, psi]
	τ	shear stress [MPa, psi]

Comparative stress

where:

	σ 1 , σ 3	normal stress [MPa, psi]
	τ	shear stress [MPa, psi]
	α 1 , α 2	conversion factors of the weld joint [-]

Meaning of used variables:

A	throat area of the weld group [mm 2 , in 2 ].
F Z	axial force [N, lb]
F Y	bending shearing force [N, lb]
e	force arm [mm, in]
W	section modulus of throat area of the weld [mm 3 , in 3 ]
M	bending moment [Nm, lb ft]
α 1 , α 2	conversion factors of the weld joint [-]