DESIGN OF WELDED JOINTS:
1) DESIGN OF TRANSVERSE FILLET OR LAP JOINTS:
Fillet weld or lap joint is obtained by overlapping the plates and then welding the edges
of plates.
Let us assume that, cross-section of fillet is a right angled triangle ABC with hypotenous
'AC' making equal angles with other two sides AB and BC.
The length of each side = AB = BC = Leg or size of weld = Thickness of plate = s
Perpendicular distance of AC from point B = BD = Throat thickness = t
Length of weld = l
From right angled triangle ∆ BDC,
we have, sin (45°) =
0.707 =
𝑡
𝑠
t=0.707s
𝐵𝐷
𝐵𝐶
=
𝑡
𝑠
∴ Minimum area of weld or Throat area = Throat thickness × Length of weld
= t × l = 0.707 s × l
Transverse fillet welds are designed on the basis of tensile strength. If σt is the
permissible tensile stress induced in the weld metal, then tensile strength of welded joint is,
(a) For single transverse fillet weld, W = 0.707 ⋅ s ⋅ l ⋅ σt
(b) For double transverse fillet weld, W = 2 × 0.707 ⋅ s ⋅ l ⋅ σt = 1.414 ⋅ s ⋅ l ⋅ σt
2) DESIGN OF PARALLEL FILLET WELDS:
3) DESIGN OF COMBINATION OF PARALLEL AND TRANSVERSE FILLET WELDS:
Combination of single transverse and double parallel fillet weld is subjected to tensile
stress and shear stress.
STRESS CONCENTRATION FACTORS FOR WELDED JOINTS(FOR DYNAMIC LOADINGS):