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Page 1: Analysis of Beams _ Shear Force & Bending Moment Diagram ~ Learn Engineering

322014 Analysis of Beams | Shear Force amp Bending Moment Diagram ~ Learn Engineering

httpwwwlearnengineeringorg201308shear-force-bending-moment-diagramhtml 15

Analysis of Beams | Shear Force amp Bending MomentDiagram| |

Beams are structural members which are most commonly used in buildings Beams have numerous other applications in

case of bridges automobiles or in mechanical systems In this article we will see how we can do strength analysis of a

beam

Following article gives detailed description of the video lecture

What is a Beam In a beam transverse load is acted which in fact comes from the slabs to the column or walls It is clear from following

figure that beams are integral part of of building structure In all of the beams load acted is transverse as shown

Fig1 In beam transverse load is acted and it is an integral part of building structure

For analysis purpose beam can be considered as a part of beam column system This way we can determine external load

acting on individual beams After determining load acting on individual beam beam can be separated out from beam

column system for further analysis

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322014 Analysis of Beams | Shear Force amp Bending Moment Diagram ~ Learn Engineering

httpwwwlearnengineeringorg201308shear-force-bending-moment-diagramhtml 25

Fig2 Building structure consists of many beam-column systems beam is a part of beam-column system

Length of the beam is much higher than its lateral dimensions So axial strain developed in a beam will be very small

compared to shear strain or strain induced due to bendingThis is shown in figure below

Fig3 Axial strain in beam is negligible compared to shear strain

So for design purpose of beams analysis of shear force and bending moment induced are of at most importance The

interesting thing is that you can draw shear force and bending moment distribution along any beam by understanding

what exactly is shear force and bending moment

Both shear force and bending moment are induced in beam in order to balance external load acting on it We will go

through details of it separately

Shear ForceShear force is the internal resistance created in beam cross sections in order to balance transverse external load acting

on beam Consider following beam it does not matter from where you take a section when you add forces acting on it it

should be in equilibrium Shear force is induced exactly for this purpose to bring the section to equilibrium in vertical

direction It acts parallel to cross section

Fig4 Shear force is induced in a section to balance the external load

So just by applying force balance in vertical direction on the free body diagram we can determine value of shear force at

a particular cross section Usual sign convention of shear force is as follows

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Working of Steam Turbine

Steam turbines are heart ofpower plant they are thedevices which transformthermal energy in fluid tomechanical energy In this

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Cutting Force Analysis -

Merchants Circle

Forces experienced by a toolduring cutting is detrimentalin design of mechanical

structure of cutting machine predictingpower consumptio

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322014 Analysis of Beams | Shear Force amp Bending Moment Diagram ~ Learn Engineering

httpwwwlearnengineeringorg201308shear-force-bending-moment-diagramhtml 35

Fig5 Usual sign convention of shear force

Now we can apply same concept in different cross section and find how shear force varies along length of the beam

Bending MomentBut balance of transverse forces alone does not guarantee equilibrium of a section There is another possibility of beam

rotation if moment acting on it is not balanced If this is the case a bending moment will be induced in cross section of

beam to arrest this rotation It will be induced as normal forces acting on fiber cross section as shown

Fig6 Bending moment is induced in section to balance external moment section is zoomed in left figure for better viewing

Resultant of those forces will be zero but it will produce a moment to counter balance the external moment So we can

calculate moment induced at any cross section by balancing the external moment acting on the free body diagram

Sign convention of bending moment is as follows

Fig7 Sign convention of bending moment for simply supported case

This sign convention approach is valid for simply supported beam For cantilever case sign convention is exactly opposite

to this

With these concepts developed we can easily calculate distribution of shear force and bending moment along the length

of the beam We will see few examples

Example of CantileverConsider this case a cantilever carrying 3 loads

Fig8 Analysis of cantilever carrying 3 loads

Here we can start analysis from the free end

322014 Analysis of Beams | Shear Force amp Bending Moment Diagram ~ Learn Engineering

httpwwwlearnengineeringorg201308shear-force-bending-moment-diagramhtml 45

Section A-B

So for between A and B if you take a section the only external force acting on it is F1 So a shear force should induce in

section to balance this force So value of shear force between A and B is F1 But force balance alone does not guarantee

equilibrium of the section There is an external moment on the section So a bending moment will be induced in section

in order to balance the external moment Since value of external moment is F into x bending moment will vary linearly

Section B-C

Between B and C effect of force F2 also comes So shear force becomes F1 plus F2 And in bending moment effect of F2

also gets added Similar analysis is done between section C and D also So SFD and BMD of this problem would look like

this

Fig9 SFD and BMD of cantilever beam

Simply Supported CaseNow consider this problem A simply supported beam with uniformly distributed load First step here would be

determination of reaction forces Since the problem is symmetrical reaction forces will be equal and will be half of total

load acting on beam

Fig10 A simply supported beam with uniformly distributed load in it

Section A-B

Lets start analysis from point A If you take section between point A and B it should be in equilibrium So shear force will

have equal magnitude of Reaction force Bending moment gives a linear variation

Section B-C

But after point B effect of point load and distributed load come Effect of distributed load is something interesting Take

a section in BC In this section along with two point loads there is a distributed load also This distributed load can be

assumed as a point load passing through centroid of distributed load Value of point load is U( x - L3) And it is at a

distance (x - L3) 2 from section line So shear force will have one more term which comes from distributed load From

the equation its clear that shear force varies linearly

You can easily predict how bending moment varies along length from the same force diagrams Since this equation is

quadratic it will have a parabolic shape Same procedure is repeated in remaining section Since this problem is

322014 Analysis of Beams | Shear Force amp Bending Moment Diagram ~ Learn Engineering

httpwwwlearnengineeringorg201308shear-force-bending-moment-diagramhtml 55

Newer Post Older Post

symmetrical in nature SFD and BMD would also be symmetrical It is shown in figure below

Fig11 SFD and BMD of simply supported beam

Home

Learn Engineering Designed by PSD Style copy 2011 All Rights Reserved Blogger Template

copy2012-2013 Imajey The co ntent is co pyrighted to LearnEngineeringo rg amp Imajey Co nsulting Engineers Pvt Ltd and may no t be repro d uced witho ut co nsent

Pipe bending machinewwwsococomtw

Taiwan Tube Cutting Pipe Bending Sawing Deburring Chamfering

Page 2: Analysis of Beams _ Shear Force & Bending Moment Diagram ~ Learn Engineering

322014 Analysis of Beams | Shear Force amp Bending Moment Diagram ~ Learn Engineering

httpwwwlearnengineeringorg201308shear-force-bending-moment-diagramhtml 25

Fig2 Building structure consists of many beam-column systems beam is a part of beam-column system

Length of the beam is much higher than its lateral dimensions So axial strain developed in a beam will be very small

compared to shear strain or strain induced due to bendingThis is shown in figure below

Fig3 Axial strain in beam is negligible compared to shear strain

So for design purpose of beams analysis of shear force and bending moment induced are of at most importance The

interesting thing is that you can draw shear force and bending moment distribution along any beam by understanding

what exactly is shear force and bending moment

Both shear force and bending moment are induced in beam in order to balance external load acting on it We will go

through details of it separately

Shear ForceShear force is the internal resistance created in beam cross sections in order to balance transverse external load acting

on beam Consider following beam it does not matter from where you take a section when you add forces acting on it it

should be in equilibrium Shear force is induced exactly for this purpose to bring the section to equilibrium in vertical

direction It acts parallel to cross section

Fig4 Shear force is induced in a section to balance the external load

So just by applying force balance in vertical direction on the free body diagram we can determine value of shear force at

a particular cross section Usual sign convention of shear force is as follows

thermal power pla

Working of Steam Turbine

Steam turbines are heart ofpower plant they are thedevices which transformthermal energy in fluid tomechanical energy In this

video le

Cutting Force Analysis -

Merchants Circle

Forces experienced by a toolduring cutting is detrimentalin design of mechanical

structure of cutting machine predictingpower consumptio

Subscribe to Our News

Letter

Template Hits

342922

Pre EngineeringBuildingssaturnsteelinEnquire_Now

Manufacturer Of Pre Engineered

Buildings In Madhya Pradesh

Email address

Ab

ou

t th

is A

d

Trust Rating

Not Yet Rated

learnengineeringorg

322014 Analysis of Beams | Shear Force amp Bending Moment Diagram ~ Learn Engineering

httpwwwlearnengineeringorg201308shear-force-bending-moment-diagramhtml 35

Fig5 Usual sign convention of shear force

Now we can apply same concept in different cross section and find how shear force varies along length of the beam

Bending MomentBut balance of transverse forces alone does not guarantee equilibrium of a section There is another possibility of beam

rotation if moment acting on it is not balanced If this is the case a bending moment will be induced in cross section of

beam to arrest this rotation It will be induced as normal forces acting on fiber cross section as shown

Fig6 Bending moment is induced in section to balance external moment section is zoomed in left figure for better viewing

Resultant of those forces will be zero but it will produce a moment to counter balance the external moment So we can

calculate moment induced at any cross section by balancing the external moment acting on the free body diagram

Sign convention of bending moment is as follows

Fig7 Sign convention of bending moment for simply supported case

This sign convention approach is valid for simply supported beam For cantilever case sign convention is exactly opposite

to this

With these concepts developed we can easily calculate distribution of shear force and bending moment along the length

of the beam We will see few examples

Example of CantileverConsider this case a cantilever carrying 3 loads

Fig8 Analysis of cantilever carrying 3 loads

Here we can start analysis from the free end

322014 Analysis of Beams | Shear Force amp Bending Moment Diagram ~ Learn Engineering

httpwwwlearnengineeringorg201308shear-force-bending-moment-diagramhtml 45

Section A-B

So for between A and B if you take a section the only external force acting on it is F1 So a shear force should induce in

section to balance this force So value of shear force between A and B is F1 But force balance alone does not guarantee

equilibrium of the section There is an external moment on the section So a bending moment will be induced in section

in order to balance the external moment Since value of external moment is F into x bending moment will vary linearly

Section B-C

Between B and C effect of force F2 also comes So shear force becomes F1 plus F2 And in bending moment effect of F2

also gets added Similar analysis is done between section C and D also So SFD and BMD of this problem would look like

this

Fig9 SFD and BMD of cantilever beam

Simply Supported CaseNow consider this problem A simply supported beam with uniformly distributed load First step here would be

determination of reaction forces Since the problem is symmetrical reaction forces will be equal and will be half of total

load acting on beam

Fig10 A simply supported beam with uniformly distributed load in it

Section A-B

Lets start analysis from point A If you take section between point A and B it should be in equilibrium So shear force will

have equal magnitude of Reaction force Bending moment gives a linear variation

Section B-C

But after point B effect of point load and distributed load come Effect of distributed load is something interesting Take

a section in BC In this section along with two point loads there is a distributed load also This distributed load can be

assumed as a point load passing through centroid of distributed load Value of point load is U( x - L3) And it is at a

distance (x - L3) 2 from section line So shear force will have one more term which comes from distributed load From

the equation its clear that shear force varies linearly

You can easily predict how bending moment varies along length from the same force diagrams Since this equation is

quadratic it will have a parabolic shape Same procedure is repeated in remaining section Since this problem is

322014 Analysis of Beams | Shear Force amp Bending Moment Diagram ~ Learn Engineering

httpwwwlearnengineeringorg201308shear-force-bending-moment-diagramhtml 55

Newer Post Older Post

symmetrical in nature SFD and BMD would also be symmetrical It is shown in figure below

Fig11 SFD and BMD of simply supported beam

Home

Learn Engineering Designed by PSD Style copy 2011 All Rights Reserved Blogger Template

copy2012-2013 Imajey The co ntent is co pyrighted to LearnEngineeringo rg amp Imajey Co nsulting Engineers Pvt Ltd and may no t be repro d uced witho ut co nsent

Pipe bending machinewwwsococomtw

Taiwan Tube Cutting Pipe Bending Sawing Deburring Chamfering

Page 3: Analysis of Beams _ Shear Force & Bending Moment Diagram ~ Learn Engineering

322014 Analysis of Beams | Shear Force amp Bending Moment Diagram ~ Learn Engineering

httpwwwlearnengineeringorg201308shear-force-bending-moment-diagramhtml 35

Fig5 Usual sign convention of shear force

Now we can apply same concept in different cross section and find how shear force varies along length of the beam

Bending MomentBut balance of transverse forces alone does not guarantee equilibrium of a section There is another possibility of beam

rotation if moment acting on it is not balanced If this is the case a bending moment will be induced in cross section of

beam to arrest this rotation It will be induced as normal forces acting on fiber cross section as shown

Fig6 Bending moment is induced in section to balance external moment section is zoomed in left figure for better viewing

Resultant of those forces will be zero but it will produce a moment to counter balance the external moment So we can

calculate moment induced at any cross section by balancing the external moment acting on the free body diagram

Sign convention of bending moment is as follows

Fig7 Sign convention of bending moment for simply supported case

This sign convention approach is valid for simply supported beam For cantilever case sign convention is exactly opposite

to this

With these concepts developed we can easily calculate distribution of shear force and bending moment along the length

of the beam We will see few examples

Example of CantileverConsider this case a cantilever carrying 3 loads

Fig8 Analysis of cantilever carrying 3 loads

Here we can start analysis from the free end

322014 Analysis of Beams | Shear Force amp Bending Moment Diagram ~ Learn Engineering

httpwwwlearnengineeringorg201308shear-force-bending-moment-diagramhtml 45

Section A-B

So for between A and B if you take a section the only external force acting on it is F1 So a shear force should induce in

section to balance this force So value of shear force between A and B is F1 But force balance alone does not guarantee

equilibrium of the section There is an external moment on the section So a bending moment will be induced in section

in order to balance the external moment Since value of external moment is F into x bending moment will vary linearly

Section B-C

Between B and C effect of force F2 also comes So shear force becomes F1 plus F2 And in bending moment effect of F2

also gets added Similar analysis is done between section C and D also So SFD and BMD of this problem would look like

this

Fig9 SFD and BMD of cantilever beam

Simply Supported CaseNow consider this problem A simply supported beam with uniformly distributed load First step here would be

determination of reaction forces Since the problem is symmetrical reaction forces will be equal and will be half of total

load acting on beam

Fig10 A simply supported beam with uniformly distributed load in it

Section A-B

Lets start analysis from point A If you take section between point A and B it should be in equilibrium So shear force will

have equal magnitude of Reaction force Bending moment gives a linear variation

Section B-C

But after point B effect of point load and distributed load come Effect of distributed load is something interesting Take

a section in BC In this section along with two point loads there is a distributed load also This distributed load can be

assumed as a point load passing through centroid of distributed load Value of point load is U( x - L3) And it is at a

distance (x - L3) 2 from section line So shear force will have one more term which comes from distributed load From

the equation its clear that shear force varies linearly

You can easily predict how bending moment varies along length from the same force diagrams Since this equation is

quadratic it will have a parabolic shape Same procedure is repeated in remaining section Since this problem is

322014 Analysis of Beams | Shear Force amp Bending Moment Diagram ~ Learn Engineering

httpwwwlearnengineeringorg201308shear-force-bending-moment-diagramhtml 55

Newer Post Older Post

symmetrical in nature SFD and BMD would also be symmetrical It is shown in figure below

Fig11 SFD and BMD of simply supported beam

Home

Learn Engineering Designed by PSD Style copy 2011 All Rights Reserved Blogger Template

copy2012-2013 Imajey The co ntent is co pyrighted to LearnEngineeringo rg amp Imajey Co nsulting Engineers Pvt Ltd and may no t be repro d uced witho ut co nsent

Pipe bending machinewwwsococomtw

Taiwan Tube Cutting Pipe Bending Sawing Deburring Chamfering

Page 4: Analysis of Beams _ Shear Force & Bending Moment Diagram ~ Learn Engineering

322014 Analysis of Beams | Shear Force amp Bending Moment Diagram ~ Learn Engineering

httpwwwlearnengineeringorg201308shear-force-bending-moment-diagramhtml 45

Section A-B

So for between A and B if you take a section the only external force acting on it is F1 So a shear force should induce in

section to balance this force So value of shear force between A and B is F1 But force balance alone does not guarantee

equilibrium of the section There is an external moment on the section So a bending moment will be induced in section

in order to balance the external moment Since value of external moment is F into x bending moment will vary linearly

Section B-C

Between B and C effect of force F2 also comes So shear force becomes F1 plus F2 And in bending moment effect of F2

also gets added Similar analysis is done between section C and D also So SFD and BMD of this problem would look like

this

Fig9 SFD and BMD of cantilever beam

Simply Supported CaseNow consider this problem A simply supported beam with uniformly distributed load First step here would be

determination of reaction forces Since the problem is symmetrical reaction forces will be equal and will be half of total

load acting on beam

Fig10 A simply supported beam with uniformly distributed load in it

Section A-B

Lets start analysis from point A If you take section between point A and B it should be in equilibrium So shear force will

have equal magnitude of Reaction force Bending moment gives a linear variation

Section B-C

But after point B effect of point load and distributed load come Effect of distributed load is something interesting Take

a section in BC In this section along with two point loads there is a distributed load also This distributed load can be

assumed as a point load passing through centroid of distributed load Value of point load is U( x - L3) And it is at a

distance (x - L3) 2 from section line So shear force will have one more term which comes from distributed load From

the equation its clear that shear force varies linearly

You can easily predict how bending moment varies along length from the same force diagrams Since this equation is

quadratic it will have a parabolic shape Same procedure is repeated in remaining section Since this problem is

322014 Analysis of Beams | Shear Force amp Bending Moment Diagram ~ Learn Engineering

httpwwwlearnengineeringorg201308shear-force-bending-moment-diagramhtml 55

Newer Post Older Post

symmetrical in nature SFD and BMD would also be symmetrical It is shown in figure below

Fig11 SFD and BMD of simply supported beam

Home

Learn Engineering Designed by PSD Style copy 2011 All Rights Reserved Blogger Template

copy2012-2013 Imajey The co ntent is co pyrighted to LearnEngineeringo rg amp Imajey Co nsulting Engineers Pvt Ltd and may no t be repro d uced witho ut co nsent

Pipe bending machinewwwsococomtw

Taiwan Tube Cutting Pipe Bending Sawing Deburring Chamfering

Page 5: Analysis of Beams _ Shear Force & Bending Moment Diagram ~ Learn Engineering

322014 Analysis of Beams | Shear Force amp Bending Moment Diagram ~ Learn Engineering

httpwwwlearnengineeringorg201308shear-force-bending-moment-diagramhtml 55

Newer Post Older Post

symmetrical in nature SFD and BMD would also be symmetrical It is shown in figure below

Fig11 SFD and BMD of simply supported beam

Home

Learn Engineering Designed by PSD Style copy 2011 All Rights Reserved Blogger Template

copy2012-2013 Imajey The co ntent is co pyrighted to LearnEngineeringo rg amp Imajey Co nsulting Engineers Pvt Ltd and may no t be repro d uced witho ut co nsent

Pipe bending machinewwwsococomtw

Taiwan Tube Cutting Pipe Bending Sawing Deburring Chamfering