and welcome once again to this course on principles of construction management and today in the
ninth session that we have we basically discuss the case study of the boundary wall what i
thought was that before we get into the other modules like accounts or scheduling or safety
its important for us to go through this example even though its a very simple example in a
little bit of detail so that you have a better appreciation of what we are talking about
so this discussion today will be largely confined to the discussion in the boundary wall and
we will look at the whole case in a little bit of detail
so now going to the details of that this is what we had used this was the case study here
we have a twenty meter and a fifteen meter here and ten meter here and another ten meters
here so we had a fifty five meter boundary wall with rc pillars reinforced concrete pillars
and the dimension of this rc pillar has been chosen as two thirty into three hundred two
thirty having been chosen basically to coincide with the width of this brickwork so that the
plastering can be done uniformly on the pillar as well as the wall this was the section that
we had used for this boundary wall where we had said that there will be a fifteen mm thick
plaster and this here of course is only the brickwork but of course there will be rc pillars
is well at certain locations then we have this offsets in the brickwork
we have this angle which is fixed to the pillars here we have the details of the rc pillar
and the foundation this is what we used to do the quantity estimation and the embedment
length used or the depth used was a hundred and fifty mm which was probably not mentioned
in the drawing at that time but it was used in one of the conditions that we give so once
we understand this drawings a little bit better lets try to understand what are the different
items of work that are involved what are the different activities that will go on in the
construction of this boundary wall we will not talk about the procurement of materials
and so on but we will only talk about the actual activities that go on in order to be
able to make this boundary wall so the first thing that we have to do is earth
work so at the end of it in order to be able to construct the boundary wall we will have
to do some earth work we will have to remove some earth in order to be able to make the
footings or be able to do the offsets of the foundations for the brickwork then there is
an activity called laying the pcc the play cement concrete this has to be done below
the brickwork as well as below the rcc footings then we have the brickwork even though when
we were estimating the quantities we used brickwork as a single unit and said all the
brickwork can be done together lets just get the quantity but from an operational point
of view we are talking of brickwork below the ground level we will soon see the importance
of breaking up the brickwork into below ground level and above ground level apart from the
brickwork there is the plastering on the walls so this plastering as you mentioned a few
minutes ago has to be done on the walls as well as the pillars then there is the back
filling of the earth now obviously if you remember the section
of the brick wall this is what we have we would have excavated this amount of earth
and after completing this brickwork here this earth has to be backfilled so there is a back
filling activity which is involved which is separate as far as the payments are concerned
or as far as the quantity estimation is concerned we have clubbed the payment for back filling
as part of our earthwork that you will see if you read the description of the earthwork
that was given then we have removal of excess earth after all a certain amount of space
below ground level has been consumed or has been used by either the brick wall or the
column and the footing so that amount of excess earth has to be transported
now where that has to be transported was another matter of discussion when we talked about
the description we said that that earth if it is to be transported within five hundred
meter within a kilometer within two kilometers and so on that will have different rates as
far as the construction of the boundary wall is concerned this is a specific item which
has to be undertaken continuing with that there is this issue of fabrication of angles
now these angles which we have to fix on top of all these pillars have to be cut they have
to be rounded off and all the kind of shaping has to be done holes have to be drilled and
so on so this is another activity which has to be
completed before the boundary wall can be completed then we have of course the fixing
of angles on the column tops and fixing of barbed wires once the angles have been fixed
if we continue with this there are other items like plastering the top of the boundary wall
now this is something which if you recall was not estimated was not counted when we
were doing the estimation of the quantity of plastering in the boundary wall construction
but thats a small amount of plastering and that we will talked about it separately later
on in this discussion another entirely different line of activity
or a set of activities is preparation of reinforcement for the footings see what happens is that
this reinforcement that is the reinforcing steel or the bars of different diameters will
be ordered and procured they will be brought to site and finally somebody has to cut them
according to the cut lengths and arrange them so this i have broken up into the reinforcement
for the footings and apart from the footings there is preparation of the reinforcement
for columns and this has been divided into one two and three as we will see and this
has to be ready before the footing can itself be cast for the simple reason that if you
recall the section the footing is like this there is a column here and before you can
cast this footing even though the reinforcement for the footing is somewhere here you cannot
cast this footing unless at least some amount of reinforcement for the columns here including
maybe the links has been buried in the footing so before you can cast the footing you have
to be ready with at least this amount of reinforcement for the columns also continuing from there
we have the reinforcement for columns up to ground level now let me tell you what is the
significance of the ground level if we are able to complete the brickwork and the rc
work up to ground level then we can start doing the back filling because unless that
is completed the back filling cannot start so one of the reasons actually for doing this
exercise today in going through the construction of the boundary wall in more detail is to
introduce you these ideas of dependence the idea that all these activities cannot be taken
up together some of them can be because they are independent but some of them depend on
the completion of other activities and so on
so this is the second set of reinforcement for the columns and then we have the third
set which goes up to the top of the column of course in this particular example the total
height is not so large and therefore maybe we can do this and this together maybe in
fact we can do all of them together but the point of breaking them down and discussing
them with you like this is to show that in a larger project these are the kind of things
these are the kind of considerations which operate on your mind when we are trying to
manage that project and then we go to the actual concreting work that is we are talking
of reinforced concrete being placed in footings you would recall that as far as the pcc is
concerned that we have covered already i think it was activity two or something just of the
earthwork now we are mentioning placing structural concrete
in footings similarly we have a structural concrete in columns up to ground level the
reason for choosing the ground level i have already discussed with you just now and then
we have reinforced concrete in columns up to the top of column now here i have not tried
to separate the portion where the angle has to be fixed there can be a situation where
the column is like this the fact of it remains that we will need to fix the angle here so
there is a possibility that in a certain situation you may say well we are not ready with the
angles yet and therefore can we do the concreting up to this part and do this part later on
once we have been able to fix the angle and then we will pour this
but in this example i have said no we will put the angle here and then from the ground
level up to the top of column we will club it as a single activity so now lets try to
talk about some questions what should be the sequence of work what should be the order
in which the activities are to be taken up now obviously you can see from the list of
activities that we have considered some of them are independent and some of them depend
on previous activities or other activities to be completed so thats what the sequence
of activities is so now what governs the sequence of work is what we will see in the discussion
subsequently are there any dependencies thats number one
the second thing is what are the resources required what we would like to do is ensure
contiguity of resource deployment see each activity requires certain resources in terms
of manpower equipment maybe material and we would not like to have a situation that over
a period of time a one resource is required here and then it it is required here so during
this period the resource will be idling at site otherwise we will have to bring the resource
here and then bring it again here so it would be easier and perhaps operationally a lot
better if these two activities could be scheduled in a manner that once this activity is done
the resource is used again here and then the resources returned possibly for use in another
site an entirely independent thing at what stage should payment be made to the contractor
we must remember that at the end of it the whole idea of doing the estimation exercise
was that ok if we want to construct this boundary wall how much is the contract are going to
be paid now at what stage should the payment be made should it be made only upon the completion
of the project that is only after the entire boundary wall has been made the payment is
made in a single installment or there could be intermediate stages and then if there are
intermediate stages what should be the basis of making the payment we must remember that
in making payments one has to be careful to make sure that the process is transparent
and reasonable we must make sure that the contractor has
enough resources to continue with the work but at the same time he has not been overpaid
that is he has not been paid for an activity which has not been completed or the client
should still have funds which are owed to him and not to the contractor now apart from
this there are some other aspects of detailed planning which we will investigate in our
discussion today now as far as the first part is concerned that is the sequence of activities
in terms of dependencies this is the list of nineteen activities that we talked about
now some of these dependencies and the absence of those dependencies is very clear and for
each activity we would really like to know which of the other activity should have been
completed before that activity can be taken up for example we cannot do the pcc unless
the earthwork has been completed now the question is whether the entire fifty five meter of
earth work should be completed before the pcc can be started thats not really true but
you need a certain amount of reasonable front so that the pcc operation can start similarly
you cannot do the brickwork above ground level unless you have completed the brickwork below
ground level so some of these things are very obvious and
usually the dependency is shown in the following format we have a list of activities abcde
and so on and we would list here in this column on what other activities does this particular
activity depend for example the way i have shown it here a and b do not depend upon anything
whereas c depends on a d depends on a and b e depends on b and c and so on so this of
course a remarks column and we want to write something we can say something here but what
i would like you to do is to try to put down the dependencies of the nineteen activities
listed for the boundary wall construction in the above format
so what you do is you go back to this nineteen activities and try to complete this in this
format you list the nineteen activities here and list on which activities they depend please
remember that there is no unique solution to some of these things there is no reason
why only these nineteen activities are important or the project can be broken up into nineteen
activities and not eighteen why it should be not twenty one that would depend for example
on in how many lifts do we want to talk about brickwork whether we want to do the plastering
before or after the completion of the brickwork and the reinforce concrete work or you would
like to do the plastering of concrete as it is completed and then do the plastering for
brickwork and so on there is no unique solution to that and thats
something which we have to see let us look at the sequencing of work from the point of
view of contiguity of resource deployment in both the pcc that is a plain cement concrete
and the reinforce cement concrete work a concrete mixer is required and related labor is required
so there is a set of skills in the labor that we want as far as concrete work is concerned
and therefore it will help us in completing the project if the pcc and the rcc work are
taken up together to the extent that they can be and are completed in a manner that
the concrete mixer can be returned or transferred to another site and the related labor can
also be released the vibrator for example is required only
for the rcc work so when will we start the rcc work we should endeavor to schedule the
rcc work in a manner that it is continuous so that the vibrator which has been brought
to site can also be used and then returned we have talked about the plastering before
is well plastering on the wall and the pillars and also the top of the wall would require
the same resources and therefore we would like to start the plastering once a lot of
things are ready so that the group of people the labor which is engaged in the plastering
work can have work continuously we have talked about backfilling of excess
earth and that also can be started after both the columns and the brickwork have been completed
till the ground level of course there is an option depending on the distance between the
concrete pillars we may hold back the back filling in one or the other side that is we
may do the back filling for the brickwork and not do it for the rc footings or do it
for the rc footings and not do it for the brickwork but thats something which relates
to the discussion we were having earlier that there is no unique solution there is no unique
activity that it can be assigned but as a project manager or a manager at the site you
have to understand that whether you want to break it up the more activities you want to
break it up or complicated your network becomes then more complicated your thought process
becomes so we should try to make it simple but at
the same time it should not be made simple beyond a point continuing with this discussion
on backfilling backfilling can be completed only after the plastering in the hundred millimeters
has been done because what we have is that here is the wall this is where the ground
has to be finished but what we have said is that the plastering should extend a hundred
mm below ground level so this back filling here can be completed only after this plastering
has been completed so thats something which we need to keep at
the back of our mind we may say that well we will do most of the back filling but let
the ground be like this so that once we do the plastering we complete the plastering
here and then do this small amount of back filling later on so these are small things
which as a manager at a site you can always do now continuing that discussion what are
the other considerations that could determine the sequence of work before the final left
of the column is caused the angles for supporting the barbed wires have to be in place i explained
this to you earlier as well even at the time of casting of the footings the reinforcement
in the first lift of the columns has to be in place this also i have discussed with you
earlier so now we come to this discussion on what
stage the payment should be made given that the construction project goes on for long
periods of time its only reasonable that intermediate payments are made to contractors at intervals
with appropriate deductions so whatever the deductions that are admissible they have to
be made as we go along it cannot happen that we make the payments without making the deductions
and think or push all the deductions to be made towards the final bill funds are held
back to be used towards defect liability default etcetera by the contractor i went over this
a little while ago and as far as the basis of intermediate payment is concerned the amount
of work in terms of the quantities of the different items of work completed or it can
be done in terms of the percentage of total work completed
what it means effectively is that if the boundary wall has a contract value of fifteen lakhs
then an intermediate payment can be made either depending on the amount of work completed
for the different items which means that they have to be measured earthwork brickwork pcc
rcc and so on and so forth or in terms of the total length of the boundary wall and
that is exactly whats being said here when it comes to the first part it is the quantities
of the different items of work completed and they have to be jointly agreed between the
contractor and the client and payments are made accordingly because for each of the items
there is a certain rate which has been agreed upon
so we can always make a judgment as to how much is the value of the total work completed
at a given point in time when we are making the intermediate payment now as far as the
percentage of total work is concerned this has to be defined in the case of the boundary
wall it could be related to the meters of the wall completed so we can say that well
if the fifty five meter boundary wall costs fifteen lakhs and fifteen meters has been
completed therefore a certain fraction of that has been completed and we make a payment
for that but please remember that if we adopt the latter part that is we are going by the
percentages then the wall has to be completed in all respects for those fifteen meters that
is right up to the fixing of the angle and possibly even the barbed wire
so one has to be careful as to what is the kind of contract that we deal with and thats
something which we will probably go into at a later stage in this course the types of
contract and the relationship with the schedule of payments now let me give you some homework
just to think about it do all the twenty three footings have to be completed before starting
on the construction of the columns the answer is obviously no we can complete a certain
amount of footings and start casting those columns so that at least the other things
can carry on similarly will the brickwork be easier if
the concrete columns are completed first or the brickwork can be done first and the brickwork
allowed to serve as the shuttering on two sides for the columns what is being said here
is that we have brickwork here on both sides and we have the rc pillar so one way to do
things would be to complete the rc pillar first and then do the brickwork or we could
do the brickwork first and then do the rc pillar now if you bring the brickwork all
the way up to here then there is no place to put the shuttering plate in fact this brickwork
will serve as the shuttering for these two sides and as far as the rc pillar is concerned
we need to put shuttering only on the two sides
now in case the brickwork is allowed to serve a shuttering should the payment for the shuttering
be made for two sides or for all the four sides when we were calculating the amount
of shuttering required for these columns we have assumed that all the four sides will
have a shuttering now if we find it convenient to do the brickwork and let the brickwork
serve as the shuttering for the concrete so be it the issue is whether the payment should
be made or not i am not commenting about it right now we will probably talk about it sometime
later and thats why these questions are food for thought
there is no real specific answer there is no true answer to some of these questions
they are open ended and one has to be making a judgment at site at a lot of times and those
judgments have to be made in accordance with the principles and the rules formally laid
down in the contract so we have not gone into the contract the details of the contract what
we have said is that what is legitimately done is to be paid so in this case if only
two sides of the shuttering has been used it makes sense to say that well we will make
payment only for the two sides what the implications of that is in terms of the overall contract
is something which we talk about separately now lets continue with the discussion on the
homework in the illustrative example of the boundary wall the data is such that bars of
a certain diameter are being used only in one application so we have bars which are
going to be used like this that is the footing then we have the column reinforcement and
we have the links so in this case the diameters for these three applications was all different
but of course in a real project there could be a real need to optimize the cutting of
bars from the lens available to minimize the wastage not only the wastage but also see
that well if we have a certain amount of reinforcement available for one application should it be
not diverted to another application which also uses bars of the same diameter
so for example in a certain case bars are available in lengths of six meters now i leave
it to you to think what governs the length of bars available at site they are to be procured
from the market and what governs the total length of the bars which is available in the
market now the cut length for example for individual bars is twenty four hundred in
an l shaped bar with a four hundred mm shorter side so we are talking of a situation where
the two thousand is the longer length the four hundred is the shorter length and the
cut length for this is twenty four hundred not counting for any kind of changes that
may happen on account of the bend now its also given that the laps where needed
is eight hundred mm those of you who are familiar with principles of reinforced concrete design
would know that there is something called a lap length and if suppose it is given that
the lap should be at least eight hundred mm then the question is how do we optimize the
bars the availability is six meters the cut lengths is given other conditions like the
lap lengths is given and we need to find out how best to use the bars please note that
the bar bending schedule will usually show only the final completed length the bar bending
schedules often do not show the location of laps or how many laps to be provided and so
on and that is left to the judgment of the site engineer
so now given that the bars are available in six meter lengths and the cut length is twenty
four hundred what we do is we make one bar out of this and we make another bar out of
this so that makes the two bars having a length of forty eight hundred mm and the question
is how best to use the remaining twelve hundred millimeters of the bar now continuing lets
talk of something very very different recall that we did not include the provision for
the angles at the top of the wall in our discussion though they were provided for in the drawing
this was something which i had left out and said that you can do it on your own
now if this happens in a real case what do we do we could have gone ahead and floated
the tender and even avoided the job before this oversight was discovered so that means
we would have draw up the estimate awarded the contract without having the item for providing
the angles now calculations for the rate of this item would then become what is called
an extra item and we would need to do the rate analysis as we have discussed in a previous
class as to what is a reasonable rate for providing these angles
similarly plastering on the top of the boundary walls was not included in our calculations
of the estimate obviously the client can ask the contractor awarded the job for the boundary
wall to carry out this plaster also at the rate agreed for plastering in the other parts
this is an example of additional work what we had in the case of the angle was an extra
item which was not provided for in the contract and we are asking the contractor to do it
in this case we are asking the contractor to do additional work in terms of providing
plaster at the agreed rate at a location which was not indicated in the drawing
in short whether an extra item or additional work the cost should not normally deviate
or exceed from the original estimate by a large margin so this is the bottom line that
in most contracts there will be some extra items there will be some additional items
but what has to be ensured is that the total cost of the project does not deviate from
the contract value by a large amount now how much is that large amount is something which
may vary from organization to organization now in this discussion coming to an end having
gone through some of the details of a simple construction project with the example of the
boundary wall we are now ready to start discussion of some of the financial and economic aspects
of construction management with this example i hope you understand the details of the work
the dependencies the fact that all the work does not have to be started at the same time
the contractors have to be paid periodically and this periodic payment can be made on the
basis of the work completed and so on so with this discussion we are ready to get started
with more detailed discussion on aspects relating to finance and economics
thank you