design of welded type connections

1. Sanjivani Rural Education Society’s
Sanjivani College of Engineering, Kopargaon-423 603
( An Autonomous Institute Affiliated to Savitribai Phule Pune University, Pune)
NAAC ‘A’ Grade, NBA Accredited, ISO 9001:2015 Certified
Unit I : Welded type of Connections
By
Prof V M Mahajan (Asst. Professor)
Department of Civil Engineering
Email Id: mahajanvalmik@sanjivani.org.in

2. Introduction to Welded Conections-
 When two structural members are
connected by means of weld, the connection
is said to be welded connection.
 The element to be connected are brought close
and te metal is melted by means of electric arc
or Oxy-acetylene flame along with weld rod
which acts as filler material to the joint and
after cooling a bond is formed between
parent material and new connected element.
 Intense heat is produced to reduce metal to liquid state by an electric arc.
 This heat at the tip of rod melts the filler material and base metal thus liquefying them to
common pool called as carter.
Source:https://i.redd.it/6vxwkkqf0hh21.jpg

3. Advantages of welded connections-
 Due to absence of cover plates, gusset plates or connecting angles the
connection is lighter.
 No holes are required so process is fast.
 More adaptable than bolting.
 Efficiency upto 100% can be achieved.
 Appearance and elegance of joint is good.
 Joint are air and gas tight.
 Joints are rigid.
 Alterations and future expansion is easy.
Disadvantages-
 Possibility of brittle fracture as joints are over rigid.
 The inspection of joint strength requires NDT.
 Skilled labours are required.

4. Types of Welded Joints-
1) Butt Weld-
It is also known as groove welding.
Adopted when joints are lined up.
2) Fillet Weld-
This are used when two members
to be connected are in different planes.
This situation frequently occurs
within structure therefore are most
commonly used.
Classified based on shape of weld face.
(Convex, Concave, Meter)
Sin 450 = t/s
t = 0.705 X s
Leg=Size
Leg=Size= s
Throat Thickness
450
t

5. 2) Slot and Plug Weld-
These are used to supplement the
fillet weld. When the required length
of fillet weld cannot be provided slot
or plug weld is used.
Slot- A slot is made to the connection plate
and kept above the other plate to be connected.
Welding is provided circumferentially to
the length of slot.
Plug- is a small hole made either circular
or rectangular and entire hole is filled
with welding material.

6. Specifications for Welding- (Cl.No. 10.5 Pg.No. 78 IS 800: 2007)-
 The size of the butt weld shall be as per depth of root penetration.
 The effective throat thickness of fillet weld should not be less than 3mm and not exceed
to 0.7t to 1.0t.
 Minimum size of fillet weld-(Table No 21, pg no.78)
 Fillet welds terminating at the ends should
be returned continuously around the corners
for length not less than 2s.
 Minimum lap length of joint should not be less than
4t or 40mm whichever is more.
 Intermittent weld- Not less than 4s or 40mm and spacing should not exceed 12t or 16t or
in no case 200mm.

7. Design stresses in weld-
 Design weld strength shall be based on its throat area and shall be=
fwd= fwn/Ɣmw
= (fu×le×t/√3×Ɣmw )
Where
fwd=Design strength of weld
fwn = nominal strength of weld
fu=Ultimate stress of the weld or material
le=length of weld
t=effective throat thickness(0.70s)
Ɣmw=Partial safety factor= 1.25 for shop & 1.50= for field.
 Weld at edges-