Piling Activity Example, Applicability of different methods to Estimate Activity Duration


Now, I would like you to read this; it is
an example in piling, and I would like you to work this out. So, what we have here is a piling activity
for a bridge. On one side you have soft soil and the other
side it is soft rock. In case, so now, this is yet another factor
which can change your production and productivity and the number of piles per abutment is 20,
length of each pile is 15 meters, the working time for the winchÉ. So, you can see here, it is a winch operated system, that they keep dropping the,
you know where you pull it, pull the winch and then you drop the hammer, and you know
grab out soil and then you start pouring the pile. The normal productivity of a winch is 1.5
meters an hour is a progress you will make, productivity in soft rock is so much. So, you can assume that this is the productivity
of soft soil. Straight forward, why do not you just do the
calculation and let . So, if you have any questions, ask me. So, what is our quantity? . So, I can take, so look at the productivity,
it is given inÉ per hour What per hour? Meter per hour. Meter per hour meansÉ Meter per hour or of pile length per hour. So, it makes sense to put my quantities in
what. Meters Meters, which means it isÉ 20 into 15 That is it. After that on your soft soil, my productivity
isÉ 1.5 meters per hour. It is soft soil 1.5-meter perÉ day per hour Normal productivity is 1.5 meters per hour. Where did you get the day from? 15 meters into hours Taking that is what, I am taking, okay there
is a point here,1.5 meters per hour which mean durationÉ 10 hours for one day 10 hours for one day, for soft rockÉ coming to be 50, 0.5 into 7, 57 and two days
and 60 days. Duration Duration is 1, 10 hours a day. 10 hours a day, 0.5 meters. So, you have a total of 300 meters. No, 300 minus 15 to pin out. 300 minusÉ 300 minus 15, because already we haveÉ 20
piles on each side per hour length. 20 20, 20 Piling for each of the abutment, so there
will be two different times that will ((Refer Time:). So, the duration for this also is 10 hours
a day. No, no, the duration is for putting 300 meters
of piling. Okay, so that is okay. The notation is same. What is the conclusion? I mean below soft soil you written it is the
same duration. So, I thought it was, both the same. Not duration, so here I am actually going
15 meters an hour or as we said, I mean 1.5, 15 meters per day. So, actually I should do 20 days. Duration is 20 days. So, duration of this thing, so total is equal
to 20 days. Here it is 65 meters, duration ofÉ Work duration 10 hours, activity duration,
how much. 60 days 60 days. Now, in one case you have 20, the other case
you have 60. So, based on some of our earlier discussion,
what would you do?. I will decrease the number of working hours. Would you decrease the number of working hours? Actually I will decrease it for soft soil,
and I will increase it for soft rock. You can do that, but let say what I mean,
let say from our project perspective I would like both durations to be roughly the same. If I decrease, see the problem were decreased
the working day duration is I am going to be paying the person the same amount for that
day. Now, productivity and orders. I will finish this on 20 days and shift the
equipment to the other side, and I have two crew working. So, on 20 days these only finish one-third
and I have two crew, they are working to try to bring this enough, so these are some of
the options you will have when you start doing things. So, let us go through this, you have aÉ We
have, this is 15É You have 15 meters per day and going in at 20 days as we calculated. If you look at it for the soft rock, we have
factored, we have taken the factored, and it comes in 60 days. So, here the other part look at is the way
we have said 20 number of piles, but we are looking at productivity asÉ So, we would,
I mean the term they would use it depending on piles diameter and length, it is dia into
dia length, but here we have just taking length assuming the dia because the diameters are
constant. Now, we can again take this with the working
time factor, and we take it again as an 8.5 instead of a 10 hour day and what was 20 now
becomes, 24 days; what 16 now becomes 71 days. So, all these shows us that even something
that is so simple can get a little more twisted, it starts getting more and more complicated
as we get variations and uncertainties from different regions. Are there any questions on what we call right
now parametric estimating? So, this is typically what we did here productivity;
quantity is parametric estimating, the most what do you think numerically sound way to
go about it and you understand the challenges behind it too. We probably at least as far as the rest of
this class goes we will not look at so much as the factoring, we will mostly take duration
as the value given and focus on doing other calculations with that. But, remember the uncertainty of getting this
duration itself is the big question mark, which sometimes causes most of the disruption
in a project schedule. When you get back into a, now looking a duration;
there are certain durations which are independent of productivity. For example, a pile load test. It has to be done, it will take a certain
time independent of, you know what you do and how you do, or you know, what is happening. The same thing is curing of concrete. I can change curing based on curing compounds,
but given a certain spec it will take it is time to cure. I mean, the accelerated curing is possible,
but again within that aspect, that is what I have to wait for. I cannot change it on the site based on a
certain; you know crew size or anything else. So, we are actually now coming back to the
various techniques which we had shown earlier for duration estimating. You can see we had expert judgment, analogous
estimating, parametric estimating, three point estimate and reserve analysis. Now, taking the first two, you know expert
judgment and analogous estimating, these are very much used in construction, but the only
problem is they do not have a real base in which people are using it today. It just comes out what we called c to the
points estimate and it continuous like that. There are more formal ways such as the Delphi
technique, you know which you have a serious of experts when you keep asking them a question,
now the question to like converge on a specific number. But, you know we have not used this into in
the level which we need to yet, but that is from the scientific perspective, but from
the, here heuristic perspective it is used significantly, and the main reason for this
is as we discussed. So, you know I will not have factored productivity
value, I will not have a number of crew, I will not know what the number of crew available
to me when I go on to a site visit. I will not know actual productivity, I only
know total quantity of work, how can I actually estimate activity duration. So, all of the arithmetic we did will not
be; we will not be able to do, and so we have to result to the expert of heuristic; that
is one, and sometimes it just does not make sense to, you know calculate all these factors. When there are experienced people, who can
actually give you a fairly good reliable estimation. I mean we did this kind of duration estimating
last week in the earlier class, how much time you need to study for a subject. So, if I take that as an example, what isÉ
Their standard estimate will give you a, based on what. heuristic expert Absolutely heuristic expert, if wanted to
make a parametric, what could I do. parametric type, the number of chapter. Number, you will start breaking down and the
number of chapters, each chapter start putting times on it you know and then, factor in your
lunch breaks, factor in this, factor in that, but sometimes the effort of making that estimate
is more than you know the number that comes you. So, you will say I am just going to say half
a day, and that is good enough. So, that is the reason the experts estimates
were used and it is very practical, and if it is used correctly, it is something that
is very valid. When we, another fact we talked about uncertainty,
you know duration three point estimate, so this is a certainly more advance. We know there is a lot of duration, I mean
all the durations we talk about are come up with uncertainty, and we have to start using
probabilistic distributions, and we have options. We can, the simple option is a three point
estimate, which says again this is an expert judgment, but not giving a single value; that
giving a three value saying, you we can call it the lowest more likely highest are you
know optimistic most likely pessimistic. So, you can have values like this, which are
based on expert judgment or if you really have data, you can go ahead and start plotting
distributions of your duration and if you start plotting distributions; obviously, you
get capturing much more information than an average. So, far we have talked about the only average
productivity, average and everything is based on average. Here we have a factored average, average for
this kind of work in this height; that is average on that, and that is how we are factoring
it from on a basic. Now, we start talking about more characterizing
it in terms of uncertainties. So, we will see both of this kind of duration
distributions, one for PERT and one for Montecarlo, later in the course. We will not discuss very much about you know
the derivation of the distributional things that we learn how to use it at that stage. So, if I go back to the techniques you know
we have actually covered all of these techniques very briefly; that is expert judgment, analogous
and three point estimate. We have covered parametric estimate in you
know more detail because it is what is structured and probably easier to use it if those numbers
are available. The reserve analysis is again like I said
a buffering technique, which is mostly based on expert judgment. So, I am not covering that in detail, like
I said there is very little material available on how one technically goes about the reserve
analysis. And to summarize, we have covered all of these
methods. We talked about the duration; we have talked
about the way to estimate; we discussed in detail the parametric methods and the applicability
of different methods. If there are questions, I will take. So, this is an important foundation to the
whole planning issue, but a lot of times not given appropriate time and we will just go
with values, which then kind of squeeze the whole thing and sometimes people actually
work backward this. We say this is the duration we want and without
actually going into resources or anything, we start plugging in the numbers which are
expected without planning the resources or the productivity and when they actually get
on to the site and try to meet that duration which they had assumed, they find they cannot,
so very important estimate which drives the whole project management. Any questions? Thank you.

Author Since: Mar 11, 2019

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