STRUCTURE ANALYSIS

Hello everyone Welcome to uhh Structural Analysis 1 This course is being offered as online

certification course An initiative by The Aimers So let us begin our course by expressing

our thanks to The Aimers making the arrangements

First let me introduce myself My name is Devraj I am an associate faculty in

department of civil engineering You can note down my email ID

throughout this course or even after that if you have anything to discuss if you have

any confusion need to be clarified you are most welcome to write to me But whenever

you write to me please make sure that the subject of email you give this

It will be easier for me to me to identify those emails This course this course is

having around 12 modules Each modules around 5 lectures Each of which 25 to

35 minutes duration Were going to start first module today You see I will give you the syllabus

of the course reference books and the notes and other resource material But since

this is the first class let us let us try to understand what is the motivation of this

course Let us try to understand that what exactly we are going to learn from this course

And if you look at in your engineering curriculum there are many courses and among

these courses where this course stands How this course is related to those courses

You see the name of the course is Structure Analysis So the word structure is

is not new to us right I mean we on on various occasions and various contexts we

do use this word structure For instance we say some time something like the the management

structure of the company is like this We do say the social and economic structure of the country is like this Sometimes

we also say that the fabric structure of the textile is like this So the word

structure we are familiar with right And we have used it in various contexts Now if

I if I see the dictionary meaning of this word then it says the arrangement of and

relations between the parts or elements of something complex This definition is very general and it includes all the applications of the word

structure engineering or non engineering But you at from engineering perspective then

probably the second definition is closer It says that a building or other object

constructed from several parts So for us structure or whenever we refer to structure

it means a building or other object constructed from several parts Okay

Now as as we have defined the word structure let us see some examples Because there

is a saying that uhh that this that one image is equals to thousand words So what I am going

to do is in next few slides I am going to show you uhh some examples for structures

Let us start with uhh the structures from ancient age

You know the concept of uhh building structures was known in ancient age as well Uhh Probably

the idea of Structure Analysis uhh was not in the form that we have today But they they

knew how to make structure as per their requirement and this is evidence from uhh from this figure

you see the first one is around 15000 years old It is made of mammoth bone structure And

the second one is again 10000 years old and the third one uhh 3600 BC

And this is one of the some of the oldest freestanding structure and if you uhh you

can Google all these structure and read their history how how those structures were made

So the concept uhh of uhh the structure was also there during uhh ancient age

All wonders of the world uhh these are very famous structures I have not given the name

of these structures because they dont need any introduction these structures You see

uhh for any subject learning from history is a very important step You imagine these

structure were built uhh during a time when the technology was not that advanced The concept

of understanding of material was not that advanced and in spite of that they could build these kind of structures

So uhh you must read the history of uhh all these structures How the design was done Uhh

How the construction took place And uhh definitely those information uhh will help you to be

a better uhh structural engineer Now uhh well uhh you see this uhh in the first row you

see some of the structures which are uhh which really common in in in in in country side

and where these are this down the second row the structures which are uhh which which are

some of the uhh well known famous uhh structures And now the structure is a mud hut what you see in a village that is also a structure

And the the worlds tallest building Burj Khalifa that is also a structure A slum where many

small small uhh many small small houses collection of many small small houses those are also

structures And this skyline that you can see uhh that is also structure The Bamboo Bridge

which is again very common in uhh countryside that is also structure And uhh these these

kind of bridge is also a structure So what point I want to make is uhh to tell you uhh the two extreme And anything falls

between this to this all are structures

Well uhh many animals are also great engineers too Uhh You see these are the some of the

structures are uhh some of the structures made by animals The first one is ant colony

then bird nest then wild comb structure then spider web silk nest by moth and then uhh

termite colony The first one is very interesting because you see there is there is an optimization

technique called ant colony optimization technique and that optimization technique is uhh is

motivated uhh from from ant colony this kind of structure Uhh If you look around you can see there are many other structures uhh made by animals

Here just I am going I am showing you some representative uhh figures

Well as we all know nature is the best engineer Uhh Some of the structures again created by

the nature Uhh Human skeleton is a great structure and for that matter skeleton of any animal

uhh is structure The next one is uhh the fish scales The body of the fish itself is a great

design because uhh the body is made in such a way the surface uhh of the scale is made

in a such a way that it helps not only to uhh to allow the fish to swim it also protect

the fish And Here two important things to be clea to be noted One is the arrangements of these

fish scales And if you take each fish scale separately and if you look into the uhh look

into the structure of fish scales that is also very fascinating Bird wings is a great

again a very fascinated structure by uhh created by uhh nature Uhh Then outer cover of snails

Uhh Tree root is again very interesting structure You know uhh the roots are such that it provides

uhh it it it holds the tree to the ground and it also provides stability to the structure

In fact ther now people are trying to make foundation of any structure uhh very similar

to uhh similar to the root structure of a tree to make it more stable The anatomy of

ant is again very interesting because you see ant can carry much much more load then

their weight And the uhh and the anatomy of of of of ant actually uhh helps them to do

that And if you study them people are trying to study the anatomy of uhh anatomy of ant

and try to make robot in such a way that it can carry more load So these are again some few examples of the structure created by the nature But if you

look around you can see several uhh several other examples as well

Okay Some of the structures you know the structure is not only associated with civil engineering

Yes civil engineering we do have structure But when we say structure it is a very general It has it has nothing to do it is not only restricted to civil engineering For instance

here the first one is again uhh is very well known It is the supporting frame for PSLV

That is also structure And this structure when we have to create this structure make this structure we need to consider all the possible loads coming from this uhh launcher Uhh International Space

Station uhh it is also a structure It is orbiting in uhh in lowered orbit And then robot yes

uhh robot is again uhh the concept of structure mechanics is very important to make robots

Uhh In next lecture we will be studying uhh degrees of freedom and we will see that uhh

these concepts of degree of freedom and constraint is very important in studying robotics

Ship is again a structure uhh these are very well known The skeleton of any vehicle if

you take that is also structure Uhh Aero plane is also a structure Again these are some examples

but there are many more uhh examples Well structure is everywhere you know Some of the example that you have seen so far uhh

is very big and But very small things that we see every day uhh they are also structure

And I am trying to collect some of them so that you can relate them uhh to your daily

life For instance say tripod of a of a uhh of a camera is a structure The seesaw it is

very co it is very common in uhh any children park That is also structure The jack lifting

jack is a structure The dish antenna that is also very common is a structure

You all might have use drafter uhh in your first year engineering drawing That drafter is also structure The chair youre sitting on and watching this video uhh or the table

where the computers are kept they everything is a structure If you are sitting on a bench in your classroom that bench is a structure You all are uhh Cycle is is a structure Ceiling

fan is a structure Even cricket bat is a structure Uhh Then the collapsible gate that is also

very common is a structure The switch board uhh there are switch you can see this switch

is also a structure Scissor is a structure Even the cloth hanger uhh that is also a structure You know the

structure is everywhere Now uhh before we before we before we uhh go further here we

I try to give you some of the examples Some of the uhh some of the photographs of of of

structures that are famous and also some of the some of the objects uhh which cannot be

cannot be uhh associated with uhh civil engineering But they are also structure Some of the objects

we use in our daily life when we see every day they are also structure

But again there is a saying that uhh figure uhh is demonstration Uhh Demonstration is

much better than figure So I am going to show you some of the objects uhh which are structure

and there is a reason uhh behind uhh behind that obj that Those objects are having pa

particular shape particular size particular feature and those features are not accidental

There is a there is a reason for that and that reason can be explained through structure mechanics For instance let us give you first example is an umbrella You know you all are familiar

with this umbrella Now if I open this umbrella open this umbrella you see this this mechanism

this mechanism is a this mechanism can be explained through through structure These

ribs that you can see they are actually different kind of structure So this uhh you can you can explain uhh through the knowledge of structure mechanics Uhh For

instance uhh this is a very fascinating example You all have seen this coffee cup right Uhh

Now if you see the rib of this coffee cup Okay there is a I dont know there uhh that

you can see it properly or not This uhh th it is folded outward it is folded Yes yes

This is folded out ward This is folded outward This is also not for uhh aesthetic There is a structure reason

to this There are two things important One is it is folded and it is folded outward not

inwards You go to any coffee shop take any paper cup and you see this is a common feature

that it is always folded out outward Now you ask have you asked yourself why it is folded

outward It can be explained through mechanic structure Now similar example is again a is aluminium foil Uhh Many of you probably used this aluminium

foil to store food to carry food You see what is interesting you again see these small these

these vertical ribs here these vertical ribs here Okay Again these are not for aesthetic Uhh This provides stiffen stiffener These are

actually stiffeners This make this this entire container more uhh more more more rigid So

that you can hold it properly without considerable bending So this is also from the concept of

uhh structural mechanics Similar example you take uhh you you you take uhh this water bottle

Water bottle again this this vertical vertical stiffener that you can see These are again

not for aesthetic Aesthetic is one aspect but uhh there is a structure reason to this

This provides stiffness Make it more stiff Now uhh I will I will I will tell you one

incident that uhh few days back I was visiting one uhh one of my colleagues and I saw his

4 years daughter playing with uhh building blocks These are building blocks these a building

blocks these are building blocks Okay And she was making uhh tower with this building blocks And first he uhh first she made a tower

very slender very slender tower And when she tried to hold it and carry at it could not

control and it and it fell down Then next time when she uhh started making the tower once again she made very small tower

Very uhh not that tall not that slender and she carried it I asked her why are you uhh

making it uhh that small Then she told me because if I make it uhh more slender then

it may fall again You see the 4 years daughter uhh could realize that if it is long then

it may it may fall But why it falls That can be explained by structural mechanics Now if

I hold it like this it wont fall So why when a structure become slender then it becomes unstable Uhh That can be explained

through structural mechanics Uhh This again some example This razor that is also a structure

This you see this is a very common thing you can see in uhh on the dining table This is

this is a spoon holder The spoon holder is also a structure So what point I want to make it here is we are surrounded by structures Structure is

everywhere Only thing is uhh we have to properly uhh we have to look at those object in a different

way Okay uhh now one of the one of the important role of of engineer is to build those structures

okay Now when I uhh now you know the uhh building a structure is is a process Means there are

many steps to be followed uhh before we actually have the actual structure And structural analysis

is one such step Now just to put it in more clear way uhh let me demonstrate uhh that

what uhh let me give you illustration You see consider this structure This is Lotus Temple New Delhi Again it is a very famous structure Now suppose this is

this is the final product final structure which we need to build Now what we are going to see is what are the steps that we need to make this structure Okay

Now these are some steps It always starts with concept of the structure planning of

the structure As well as this structure is concerned it is the architecture of the structure

Now this is beside another reason why uhh every architect must must have some understanding

of structural analysis Now the first is always the concept of the structure the architecture

of the structure Now once that model is ready the architecture model is ready what we need to do is we need to understand feasibility of that model

Means when when how the model how the structure may respond when it is subjected to actual

environment And that step is analysis And once the analysis is done then you need to

design the structure Design means if if you look at the structure if it is a food then

design is a recipe for that food You need to you need to you need to make the recipe

for this for for the structure So that so that this this structure can be constructed

Now once the design is done then you need to translate the design in the form of a language

that can be understood by the people who will be executing the structure or will be constructing

the structure or fabricating the structure right And this language is is design this

language is drawing As you might have heard in your engineering drawing course that uhh drawing is the language of engineer Now this drawing goes to the construction site uhh

this drawing goes to the construction site And where there are people involved who can read this drawing and execute the structure

and finally you have the structure So these are the steps need to be followed in order

to construct it These are the broad steps There are some other steps as well minute steps But these are the major steps that need to be followed Now you see uhh it is not particularly

for this structure If you take any object which needs to be constructed or fabricated or manufactured similar steps need to be followed

There may be minor variation depending on the structure but the essence of this steps

remains the same Okay so uhh this is what we are going to do uhh in this course is uhh

this step the analysis of the structure We will be having design course in the subsequence

semester I believe you already have engineering drawing Construction also you will be having in subsequent semester So this is how you are analysis is related to other other other

subjects that you may have in your engineering curriculum Okay so what we have done so far is we have uhh we have uhh defined structure what is

structure Then we have we have seen some of the examples and through those examples we

realize that uhh structure is everywhere Any small or big any object many object can be

uhh can be called as structure And one of the important role of an engineer is to build

those structure And building structure is a process Uhh It needs several steps and structural

analysis is one such step Right Now uhh then naturally the next question comes is what is structural analysis We understand

the structural analysis is a step But what is structural analysis Now next what we are going to uhh see is what is structural analysis Now instead of giving you a formal definition

of structural analysis let me uhh let me let me tell you or explain structural analysis

through a story Okay Uhh This is a very old story maybe more than 150 years old story It is a very popular story

It is a popular nursery story And uhh I am sure that many of you uhh might have uhh read

the story when you were when you were kid Uhh But still I am telling you the story because

story as such is nothing uhh nothing new in this story probably Everybody we understand

that But still this story will probably help us to look at this subject uhh in a proper

perspective Okay now the name of the story is uhh three little pigs All the uhh all the photographs all the uhh I have taken uhh from this book All the scan

copy of photographs taken from uhh this book Okay Uhh The story was like this There are

three brothers three brothers Okay Uhh They used to stay with their mother But uhh when they are grown up uhh they decided to go out and uhh live their own and make

their own houses So they uhh requested their mother to allow them to do so And then mother

said yes fine no problem you may go ahead and uhh be careful And now once they got the consent from their mother they are very happy they are very excited

because now they are going to live their life on their own And they are going to make their house uhh by uhh

Now uhh then one of these three brothers uhh name is Curly He was an engineer Okay Now

he uhh said other two brothers that yes now we are going to uhh make our own house Let

us spend some time to plan those house Uhh Let us make the house strong so that we can

protect us from from from wild wolfs But other two brothers were bit lazy They said no nothing

doing we will make the house as as fast as possible and rest of the time we will play

So what the first uhh brother did The first brother collected some straw and made a straw

house Okay He could make the house very fast and then uhh then he could he could he would

play his guitar He could play around Now uhh the next brother he collected some wooden sticks uhh and made uhh his house with

wooden sticks Okay He could also make the house very fast But on the other hand the curly who was an engineer was busy in planning the house Okay

And design the house and so he was taking a lot of time to make the house And the other two brothers was very were laughing at him And uhh was telling him unnecessary he was

wasting the time in uhh in making your house that strong Our straw house and wood stick

house is enough But Curly did not listen to them and he went ahead with his plan And finally

he uhh made a house uhh with bricks and cement Okay

Now they all made their houses They are really happy now They are excited Uhh They are they

were living in their houses And now one fine morning they were playing uhh and suddenly

they saw one wolf coming The wolf was watching them Uhh They saw the wolf coming And uhh then what happened after

seeing the wolf they all they all got scared and they rushed to their houses Uhh The first

one went to his straw house The second one to his wood wooden stick house And the third one the Curly engineer he went to his uhh brickhouse And the wolf followed them

The wolf first followed the first one who was hiding in uhh his straw house But straw was nothing it was not strong enough for wolf Uhh So the wolf just blew it off

Uhh And then the first brother realized that he is no longer safe there and then he rushed

to the other brother who was taking shelter in uhh in in in a wood stick house

But again wolf followed him and and wood stick house was also not enough not that strong

So what wolf did is uhh then wolf blew the uhh wood stick house as well And again they

realized that they are not safe Uhh Then they rushed to uhh the other brother Curly and took shelter there uhh took shelter

there And now the wolf was very overconfident and he he he the wolf thought that he can blow

off this house as well And then wolf tried hard but could not because that brick house

was very strong uhh as compared to the uhh capacity of the wolf

And eventually he could not break the house and left and left And then uhh then all the

brothers are safe and then finally Curly said to the other two brothers that uhh please

dont be lazy next time when you do anything Now uhh the story end here There are many many variants of the story But the essence

remains the same There are other names of the story as well but I found uhh from prospective

of this course This this end is relevant Now what we learn from the story You see one one

is very obvious that uhh we should not be very lazy in doing anything We have to be very careful Now uhh another important thing we will learn is again in totally you all

know probably this that when we when when we make a house Okay

We have to make we have to make the house strong such that it can withstand the attack

from potential threat For instance in this case had it not been wolf had it been a small

cat or mouse then probably straw house or wood stick house would have been enough And

they would have been safe in their those houses as well But since here the threat is wolf

straw house and wood stick house is not enough We have to make brick house So the ess so

the moral is very natural That when you now what you do is you replace the house uhh by structure and then replace

these three brothers by us engineer and replace the wolf by threat Okay So then we can see

that we have to we need to make our structure uhh sufficiently strong such that it can withstand

the attack of potential threat Right Now how do you know that uhh up rightly In order to

in order to do that in order to make the make our house very strong what we need to understand is how the structure may respond uhh when it is subjected to that threat

If we find that uhh the structure may fail uhh when it is subjected to a particular threat

we can make our structure stronger So that realization has to be there isnt it Understanding

has to be there Now structural analysis gives you that understanding Structural anjal under

analysis is a process of understanding how a structure may behave when it is subjected

to a particular environment or a particular threat Now then uhh what is structural analysis

You have a structure which is uhh subjected to a threat uhh and then uhh we want to understand

what will be the response of the structure This is Structural Analysis We will discuss more detail about different kinds of structures different kinds of responses and different

kinds of threats But but this is the Structural Analysis of the structure Okay And this flow

is for any structure any response and any threat Now if we go from this means you have a structure which is subjected to some threat and you

want to look you are looking for a response this is called forward analysis

Now there are many instances Uhh For instance you have an existing structure uhh which were

which is built maybe 50 years or thousand 50 years or 100 years ago You dont have the design of the structure All the calculations are not available Now you need to understand

uhh what will be the residual life of the structure How long you can keep this structure as it is Now uhh here you have this structure you probably know the response

But what you want to know is you want to you you you want to inversely estimate what will

be the strength of the structure or residual life of the structure So if you do that that

is called Okay So forward analysis input is threat and output would be response And if you go like this you have the response and you want to understand the properties of the

structure all the potential threat This flow is called inverse analysis Uhh In the inverse

analysis it is a separate course all together What we do in in inverse analysis your input will be the response and output will be the

threat or output will be the properties of the structure Now but in this course what we will do is our focus will be on the forward analysis

So uhh in our case structure subjected to threat and looking for the response Uhh Now

you see uhh next class we will start from uhh this slide and we will see what are the

different kinds of structures What are different kinds of structure Uhh What are the responses

we will be looking for What are the different kinds of threats And how these threat structure and responses can be idealized

So next lecture will be idealization of the structure threats and responses Uhh Here we

end the uhh our first lecture Okay Thank you very much