Download - A structure is only as strong as its
1. On the Basis of Connecting Medium
Riveted Connections
Bolted Connections
Welded Connections
Bolted-Welded Connections
Pinned Connections
CONNECTIONS IN STEEL STRUCTURES
2. According to the type of internal forces the connections are expected to transmit
Shear (semi rigid, simple) connections
Moment (rigid) connections
CONNECTIONS IN STEEL STRUCTURES
3. According to the type of structural Elements that made up the connections
Single plate angle Connections
Double web angle connections
Top and seated angle connections
Seated beam connections
CONNECTIONS IN STEEL STRUCTURES
4. According to the type of members joining
Beam to beam connections
Column to column connections (column
splices)
Beam to Column Connections
Column Base Plate Connections
CONNECTIONS IN STEEL STRUCTURES
Riveted Connections
Used for very long time.
Made up of:
Round Ductile steel bar called shank.
A head at one end
Design - very similar to bearing type of
bolted connection.
CONNECTIONS IN STEEL STRUCTURES
The installation of the rivet requires:
Heating of the rivet
Inserting it to an oversize hole
- pressure to the head.
Squeezing the plain
end by Pneumatic driver
- Round head.
On Cooling Reduces in
Length–Clamping Force.
CONNECTIONS IN STEEL STRUCTURES
Rivets are no longer used due to:
Intro of high strength bolts
Pre-Heating of rivets prior to driving.
Labor Costs
High Level of Noise
Replacing of poorly installed rivets.
CONNECTIONS IN STEEL STRUCTURES
Fastened Together primarily by Bolts.
Bolts may be loaded in:
Tension
Shear
Both Tension & Shear
Threads of bolts:
Excluded
Included
CONNECTIONS IN STEEL STRUCTURES
While under action of Shear forces, threads
of bolts may be:
Excluded – Increased
strength
Included - Relatively
Decreased stregth.
CONNECTIONS IN STEEL STRUCTURES
Two types of bolts are used in bolted connection:
Bearing type bolts
High strength friction grip bolts (HSFG)
The most common type is bearing bolts in
clearance holes, often referred to as Black Bolts.
CONNECTIONS IN STEEL STRUCTURES
Black Bolts
Ordinary, unfinished, rough,
or common bolts.
Least Expensive
Primarily - Light structures under static load such
as small trusses, purlins etc
CONNECTIONS IN STEEL STRUCTURES
Turned Bolts
Similar to unfinished bolts.
Shanks - Hexagonal Rods
Primarily - Light structures under static load such as
small trusses, purlins etc
Expensive – Limited use – Structures with no Slippage
Connections
CONNECTIONS IN STEEL STRUCTURES
Ribbed Bolts
Round head similar to Rivets.
Raised ribs parallel to the shank.
Actual Diameter - slightly Larger than the hole –
Tightly fit into the hole.
Popular – Economical in Material & Installation
CONNECTIONS IN STEEL STRUCTURES
Bolts used in Slip Critical Connections
High Strength Friction Grip (HSFG) bolts
Pretensioned – contact pressure between the surfaces.
Friction between plates – Prevents relative slip – Higher Shear Resistance.
External Force increases than friction between plates – Slip Occurs – reserve strength due to bolt.
CONNECTIONS IN STEEL STRUCTURES
Advantages
Bolting operation is Silent.
Cold Process - No Risk of fire
Quicker process than riveting
Less Man power needed.
CONNECTIONS IN STEEL STRUCTURES
Disadvantages
When Subjected to vibratory loads – loosened –
reduction of strength
Thread area at root is less – less strength
Unfinished bolts – lesser strength – less diameter.
CONNECTIONS IN STEEL STRUCTURES
Most important feature - Quality of the weld Types of Welds are:
Groove ( More reliable than others)
Fillet (Mostly used, Weaker than groove and others)
Plug (expensive – poor transmission of tensile forces)
Slot (expensive - poor transmission of tensile forces)
Plug and Slot welds – stitch different parts of members together.
CONNECTIONS IN STEEL STRUCTURES
Positions of the welds:
Horizontal
Vertical
Overhead
Flat
Welding Notations were developed by American Welding Society (AWS).
Requires Highly Skilled Labors
CONNECTIONS IN STEEL STRUCTURES
Advantages
Economical – Cost of materials and labors.
Efficiency is 100% as compared to rivets (75-90%)
Fabrication of Complex Structures – Easy – like
Circular Steel pipes.
Provides Rigid Joints – Modern Practice is of Rigid
Joints.
CONNECTIONS IN STEEL STRUCTURES
Disadvantages
No provision for expansion or contraction –
greater chances of cracking.
Uneven heating and cooling – member may
distort – may result in additional stresses.
Inspection is difficult and more costlier than rivets
CONNECTIONS IN STEEL STRUCTURES
Most connections are Shop Welded and Field
Bolted types.
More Cost Effective
Better Strength &
Ductility characteristics –
Fully welded.
CONNECTIONS IN STEEL STRUCTURES
Welded
End Plate Connection
Bolted
Purpose - used to connect the members which are required to rotate relative to each other.
Pins are cylindrical in shape, made of structural carbon steel, forged and machined to accurate dimensions
CONNECTIONS IN STEEL STRUCTURES
Two Types of Pinned Connections
Allows the connecting members - turn through large
angles, such as in machine parts, crane booms etc.
Allows rotation through
small angles, primarily due
to elastic deformation of the
members.
CONNECTIONS IN STEEL STRUCTURES
Advantages
Easy Analysis – Moment is Zero at pin.
Free to rotate – to allow for elastic deformations.
Allow for Thermal Contraction and Expansion
Secondary Stresses – Eliminated to some extent.
CONNECTIONS IN STEEL STRUCTURES
Disadvantages
Lacks rigidity - noisy joints. E,g bridge under
heavy traffic. (so used for very large spans)
Cannot resist longitudinal tension – produces
friction that prevents free turning of pins.
CONNECTIONS IN STEEL STRUCTURES
Allows the beam end to rotate without a
significant restraint.
Transfers shear out of beam
Most Common Types:
Double clip
Shear End Plate
The Tee
CONNECTIONS IN STEEL STRUCTURES
Shear Connection
Part of the connection remains stiff in shear - little restraint to motion perpendicular to its plane.
CONNECTIONS IN STEEL STRUCTURES
Double Clip (Double Angle Shear Connection)
End Plate Shear Connection
Fin Plate Connection
Designed to resist both Moment and Shear.
Often referred - rigid or fully restrained
connections - provide full continuity between
the connected members - designed to carry
the full factored moments.
Principal Reason - buildings has to resist the effect of lateral forces such as wind and earthquake.
CONNECTIONS IN STEEL STRUCTURES
Uses
Between main beams and columns, creating a
rigid frame.
Principally to resist lateral loads, however, vertical
gravity load - negative bending moments at the
ends of the beams.
CONNECTIONS IN STEEL STRUCTURES
Two Step Process
A plate is welded to secondary section (beam)
An Angle is welded to Primary Section (column or
Beam)
OR single shear plate welded to secondary
beam and bolted to Primary beam or column.
CONNECTIONS IN STEEL STRUCTURES
The angle or plate will be bolted or welded after erection of the beam.
CONNECTIONS IN STEEL STRUCTURES
Skew Plate Connection Single Angle Connection
Two angles welded or shop bolted to the web
of a secondary beam.
After erection the angles are bolted or site
welded to the primary member (beam or
column).
CONNECTIONS IN STEEL STRUCTURES
Generally used in case of moment
connections.
Two angles are provided at top and bottom of
the beam to resist moment.
Generally used for lesser moments where
heavy loads are not acting
CONNECTIONS IN STEEL STRUCTURES
Generally used in case of shear connections.
A seating angle - at bottom of secondary
beam - shop welded to the primary member.
Seating angle resists vertical shear coming
from the beam.
CONNECTIONS IN STEEL STRUCTURES
Connects beam to beam.
Two Types
Primary Beam to Secondary Beam Connection
and
Beam Splice.
CONNECTIONS IN STEEL STRUCTURES
Connects column to column.
Column splice comes under this category.
Used to connect column sections of different
sizes.
Splices - designed for both moment and shear-
unless intended to utilize the splices as internal
hinges.
CONNECTIONS IN STEEL STRUCTURES
Connects Beam to column.
Very Common
A wide range of different types are used
Fin Plates
End Plates
Web or Flange Cleats
Hunched Connections
CONNECTIONS IN STEEL STRUCTURES
Beams are normally attached using two or
more bolts through the web.
End plate connections
a single plate welded to the end of the beams
Bolted to the column flange or web - two or more
bolts pair.
CONNECTIONS IN STEEL STRUCTURES
Fin plate connections
Single Plate welded to the Column.
Beams are normally attached using two or more
bolts through the web.
CONNECTIONS IN STEEL STRUCTURES
Steel plates placed at the bottom of Columns.
Function - to transmit column loads to the
concrete pedestal.
The design of a column base plate:
determining the size of the plate.
determining the thickness of the plate
CONNECTIONS IN STEEL STRUCTURES
A layer of grout should be placed between the base plate and its support for the purpose of leveling.
Anchor bolts should be provided to stabilize the column during erection or to prevent uplift.
CONNECTIONS IN STEEL STRUCTURES
Usually cost of fabrication and erection
constitute as high as 50% of the total cost of
steel structures, per tones of material used
CONNECTIONS IN STEEL STRUCTURES