Learners will discover the key project scheduling techniques and procedures including; how to create a network diagram, how to define the importance of the critical path in a project network, and defining project activities float. Also covered are the fundamentals of Bar Charts, Precedence Diagrams, Activity on Arrow, PERT, Range Estimating, and linear project operations and the line of balance.
Independent Float
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Из курса от партнера Columbia University
Construction Scheduling
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Activity Floats
Professor Odeh introduces the types of floats in a construction project including; total float, free float, interfering float and independent float.
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Ibrahim Odeh, Ph.D., MBAInstructor, Department of Civil Engineering and Engineering Mechanics, Columbia University
Director of Research and Founder, Global Leaders in Construction Management
So moving forward.
We spoke a little bit about the Interference Float.
Another type of float I want to touch base on is the Independent Float.
This kind of activity float is actually, not shared,
they said like is the type of a float that not shared or
affected by any other activities around it.
And it can be defined as following.
The maximum amount of time that specific activity can be delayed,
without delaying the early start of the succeeding activities,
and without being affected by the allowable delay time or
period of time of the preceding activities.
So this type of a float is the most restrictive float of all types of floats.
Mathematically, we highlight it by the following equation.
The independent float equal the minimum
of early start dates of all the successors
minus the maximum late finish dates
of the predecessors, minus the duration of
the activity you are calculating that Independent Float for.
So all the successors of the activities I'm trying to calculate,
the Independent Float for, the successors will start as early as possible,
and the predecessors will be delayed as late as possible, and
then they start in that late dates.
So that will be the duration that can play with as an Independent Float,
which will be the most restrictive one.
So let's take an example here.
If I have this as part of entire network
diagram, and I'm just highlighting three activities of that diagram.
And, the blue arrows here,
it just highlight some connections with other consumption activities.
So, in that case, trying to find the independent float of activity Y.
Based on this, the minimum of early start of
activity successors of Y, which will be 22,
minus the maximum of the late finish of the predecessor.
The late start will be 15 minus the duration of
the activity we are calculating, the independent float, four.
So in this case, we do have the following,
the minimum, the early start of the successor, 22,
which is z, minus the maximum of the late finish.
Late finish of the predecessor x would be 15,
and the duration of activity y is 6 days.
So you have an independent float of one day for activity Y here.
So in that type of float, if a negative value shows, if a negative value shows,
then you need to use zero, not negative numbers, as an independent float.
That means no way for
this activity to satisfy the conditions assumed for this type of a float.
So in conclusion, if an activity with an independent
float greater than zero, that means that that activity
can start at any point between its early start and
late start, without affecting its successors and
with the worst-case scenario of having all its
predecessors starting at their late, late start dates.
In summary, I touched base quickly on the interference float and
the independent float, but they are very rare, and
rarely used in the construction industry.
Based on the literature I studied and a lot of professionals I spoke
with in the industry, they highlighted sometimes, sometimes,
it's used in some conflict and resolutions cases
that related to a delayed claim resolution, sometimes.
But I just also want to highlight it in case you heard about an interference and
independent float, you have an idea what's that all about.
But what I want to focus more on is the free float and
the total float of your activities.
So in conclusion, for our module about floats,
we differentiate between total float and
the free float to understand the amount of delay we can tolerate
without impacting the project, your construction project schedule.
And also without impacting any of the successor activities in your project.
Again, the total float refers to the entire project and
date, the free float focusing more on the immediate successor activities.
The concept and the use of the float helps us
as construction managers and project managers to keep our project on schedule.
And to use the resources from labours, as I mentioned, from machines,
from any kind of construction resources available in our project,
use them more efficiently and effectively as the project progress with time.
Another point I want to highlight here towards the end is the lack of a float or
its disappearance from our project or
from the activities along the progress of the project gives us a clear
indication that our construction project is out of control.
So you have to be careful.
Not even out of control, we need to take corrective measures so
as to get it back on track.
Additionally, by using what if scenarios, I just explained,
especially when you have software, we can understand impacts to the project.
So I highly encourage you to always have this, always in mind.
So you have to have in mind that also if,
first activity in line of any path consumes some floats.
The remaining activities will be affected and may be left without floats.
So, whenever a float will be consumed, the following activities,
it might start with the floats, so you have to be careful on that.
That's why sometimes in real world,
in cases they have some agreements in the contracts,
who is responsible to control the float on all these activities.
They give it more attention and sometimes even some projects,
they tend to hide that floats and
not showing it to be more conservative on these activities.
And not to highlight what's the flexibility we have
on any of the activities.
In softwares like Primavera P6,
you do have this kind of option to turn off and
not show such information of the total float and the free float.
So in sum, understanding floats and its types,
especially the total and the free float in our construction industry.
And to understand its uses is one industry trick
of a very successful construction manager.
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