Question

Discuss the result of the design of fillet weld for a tie member of a truss consist of an angle section ISA 100 x 75 x 8 mm of Fe410 grade, is welded to an 8 mm gusset plate. Design a weld to transmit a load equal to the full strength of the member. Assume shop welding. If the gusset plates are connected by 2 angle section ISA 65 x 65 x 6 mm back to back to the same gusset plate. Design a weld to transmit a load equal to the full strength of the member. Express your opinion on how the length of the weld are different for both the design form your results.

Answer 1

ISA 100 x 75 x 8 mm

L1 = 100mm

L2 = 75 mm

t= 8mm

design strength =

Ag = angle section 100 x 75x 8 = 13.36cm2

fy= 250N/mm2

from IS 800:2007 pg 30

min size is taken as 3mm for thickness upto 10mm and max size of weld = 8 - 1.5 =6.5 mm

1. size of weld = 6 mm
2. the throat thickness = 0.7 x size of weld = 0.7 x 6 = 4.2mm = 4.5 mm

3. design strength of weld l

lw = length of weld = 356.3 mm = 360 mm

Cxx = 3.10cm for ISA 100 X 75 X8 MM from steel table

4 distribution of weld

a=0.449 b

lw= a + b

360 = 0.449 b + b

b = 360/1.449 = 248.440 =250 mm

a = 110 mm

5 calculation of areas

Ag = 1336 mm2

A n= Ag = 1336 mm2

Avg = Avn = 360 X 8 = 2880mm2

Atg = Atn = L1 x t = 100 X 8 = 800mm2

2)

2 angle section of ISA 65 X65X6mm

L1 = L2 = 65 mm

Cxx = 1.81 cm

area = 14.88cm2

design strength =

min size is taken as 3mm for thickness upto 10mm and max size of weld = 6- 1.5 =4.5 mm

1. size of weld = 4 mm
2. the throat thickness = 0.7 x size of weld = 0.7 x 4 = 2.8mm = 3 mm
3. LENGTH OF WELD

lw = 892.908 mm = 895 mm

distribution of weld

a = 0.386 b

l = a+b

895 = 0.386b + b

b = 645.75 = 650mm

a = 245 mm