Introduction
Connections
are the most important and basic need of the steel structure or element,
without connection the steel structure cannot construct properly. Connections
connect the available standard sections of steel make huge structure. Failure
of structure can be occurred if proper connection not provided. So the design
of proper connections is important.
For
safety and economy of structure, the major portion of cost of steel structure
consists of connections.
The
Connections are provided in following cases:
· When there is
need to supply the heavy load and long span then the built-up- sections is to
be provided. In such case, this section should be connected together to get
good section.
· When longer
span, the length of standard section requires to be connected with other
section.
· At the end different members require to be connected.
Types of
connections
Connections are generally made by bolting and
welding. In field connections, bolting is commonly used, because it is simple
and economical to make. From consideration of safety bolting is appropriate in
field connections. Welded connections are easier to make and more efficient.
The types of connections provided in steel
structure,
1.
Bolted Connection
2.
Welded Connection
3.
Riveted Connection
1.
Bolted Connection
· Bolted
connections are most commonly used connections, due to flexibility in
assembling of its parts of structure and dissembling it.
· A bolt is metal
pin with head formed at one end and shank threaded at other end through which
nut can be received.
· Pieces of metals
are connected by bolt by inserting them into the holes of metals and nut should
be threaded end.
· The process of
erection of structure is faster, but the material cost is high.
· It can be done
with less and unskilled labors.
· Following types
of bolts are used in bolted connections which depend on resultant force
transferred, types of force, and force of mechanism.
Ø On The Basis Of
Resultant Force Transferred
o
Concentric Connections: if load of structural member passes through CG
(center of gravity) of the section then this types of connections are called
concentric connection.
o
Eccentric connections: if the resultant force is acting away from the CG of
the connections.
o Moment resisting
connections: if the connections are
subjected to moments is called moment resisting connections.
o
Shear Connections: when the load occurred through shear the connections
are called as shear connections.
o
Tension Connection: when the load occurred through tension on the bolts connections
are called as tension connections.
o Combined Tension Shear Connections: when bracket connection is used to connect the inclined member to the column of structure.
Ø On The Basis
Of Force Mechanism:
o
Bearing Type Connections: To transfer the force bolts bear against the hole.
o Friction Type
Connections: The force is
transferred through frictions between the plates due to tension.
2.
Welded Connection
· Welded
connections are direct and efficient way of transferring forces from one member
to the adjacent member.
· Welded
connections are done by melting base metal from parts to be joined with weld
metal, which after cooling form connections.
· Welded
connection categorized as, fillet welds or butt welds.
3.
Riveted Connection
· In modern steel
construction riveted joints are very rarely used. The design and behavior of
riveted connections are similar to bearing type of bolted construction.
· A rivet is made
up of mild steel or high tensile steel.
· The rivet shank
expands to fill the hole as being driven, so the structural rivets are driven
hot.
· For the
calculation of rivet strength, the hole diameter is used in spite of the
nominal rivet diameter. Because of that the slip is less s compared to bearing
type bolted joint.
· While cooling, the
rivet shank length reduces, due to causing some clamping force.
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