Department of
Civil Engineering
Support Reaction
Every engineering structure needs to be supported, so that, it can remain in equilibrium under any system of forces likely to act on it. These supports develop the force as Support Reaction.
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Support Reaction
Definition:
When a number of forces are acting on a beam, then the support of the beam will provide the reactions called Support Reaction.
The reactions here will keep the system in equilibrium. i.e., ΣH = 0, ΣV = 0 and ΣM = 0
A B
Reactions Beam Loads
Supports
Types of Supports
1) Simple Support or Knife Edge Support 2) Roller Support
3) Hinged Support or Pin-jointed Support
4) Fixed Support or Built – in or Encastered Support 5) Smooth Surface Support
Supports
1) Simple Support or Knife Edge Support: If
the beam rests simply on a support, then the support is simple support.
2) Roller Support: If the beam is supported on
rollers, then such a support is called as roller support.
3) Hinged Support or Pin-jointed Support: If
the beam is supported on hinge or pin then such support is called a Hinged or Pinned Support.
Supports
4) Fixed Support or Built – in or Encastered Support: If the end of the beam is fixed or
Built in, then such support is called as fixed support.
5) Smooth Surface Support: If the body is
supported or in contact with a smooth surface, then such a support is called a smooth surface support.
Support Reactions
Type of Support Support Reactions
Simple Support or Knife Edge Support
A B [1] reaction each at supports in vertical
direction
Roller Support [1] reaction at support in Vertical direction
Hinged Support or Pin-jointed Support
[2] reactions at support, one in Vertical and
other in Horizontal Fixed Support or Built – in
or Encastered Support
[3] reactions at support, one in Vertical ,
one in Horizontal and other will be a
Moment (rotational)
Smooth Surface Support [1] reaction at support Perpendicular to the surface
Support Reactions
RA RA HA A B RA RB R RA HA RA R MABeams
1) Cantilever Beam: One end of
the beam is fixed and the other end is free.
2) Simply Supported Beam:
Both the ends of the beam are simply supported.
3) Over Hanging Beam: A part
of the beam over hangs at one end or both the ends.
Beams are structural members having larger length compared to the width and depth subjected to system of load.
A B
Overhang
Loads
The forces acting on the structure or components are called Loads. Types of Loads
1) Concentrated Load or Point Load 2) Uniformly Distributed Load (UDL) 3) Uniformly Varying Load (UVL)
Point Load
Concentrated Load or Point Load:
A load acting at a point on a beam is known as Concentrated or Point Load.
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Eg: Two men standing on a beam at certain distance are considered as point load.
Uniformly Distributed Load(UDL)
A B A B
Uniformly Distributed Load (UDL):
If a beam is loaded in such way that, each unit length of the beam carries same intensity of the load, then that type of load is known as Uniformly Distributed Load.
w unit/length
w unit/length
The total load due to UDL is assumed to be acting at
A B
Uniformly Varying Load(UVL)
Uniformly Varying Load (UVL):
If a beam is loaded in such a way that, each unit length of the beam carries a uniformly varying intensity of loading, then this type of loading is known as Uniformly Varying Load.
The total load due to Uniformly Varying Load is equal to the area of load diagram and is assumed to be acting at the center of gravity of the UVL for all calculations.
A B A B
Ex: A brick wall constructed on a beam to carry pitched or sloping roof.
A B
w unit/length
Free Body Diagram
The diagrammatic representation of the body which is isolated or separated from the contact surfaces and the contact surfaces are replaced by support reaction is called Free Body Diagram (FBD).
W W W R W B W P A W P RA RB T RA A String
