Activity Floats

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From the course by Columbia University

Construction Scheduling

489 оценки

Columbia University

Construction Scheduling

489 оценки

Course 2 of 4 in the Specialization Construction Management

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.

From the lesson

Activity Floats

Professor Odeh introduces the types of floats in a construction project including; total float, free float, interfering float and independent float.

Types of Floats in a Construction Project9:48

Activity Floats9:37

Determining Total Float and Free Float6:31

Introduction to the Interfering Float9:18

Independent Float9:17

Meet the Instructors

Ibrahim Odeh, Ph.D., MBA
Instructor, Department of Civil Engineering and Engineering Mechanics, Columbia University
Director of Research and Founder, Global Leaders in Construction Management

So let's start with an example and before I move forward with an example,

while I am giving you all of the examples in this module,

I am assuming that you are aware of the following,

drawing diagram, especially the activity on node.

And identifying the critical path and the critical activities

of that project or that network and calculating the early start,

early finish, late start and

late finish, dates of all the activities that you had in your project.

You can review the modules focusing on

the logic diagrams of activity on nodes

as well as review the modules that highlight the pass, the forward and

the backward pass calculations.

So this is for example, one of

the activity on nodes diagrams that we highlighted in the previous modules, and

I want to highlight it here to relate to what you already worked on and developed.

And to build on it, so we started by how to

draw the logic relationship between all the activities then if you remembered.

We do highlight it here in the top right corner.

The key that every activity, every logic diagram has.

Which, in our case here, the key highlight that the name of the activity.

And below it is the duration.

So, for example, this activity here.

Activity.

A, the name of the activity is A, and the duration is one day.

And in the all four numbers here, we have the early start of the activity,

early finish of the activity, late start of that activity and the late

finish of the activity as we can see all the numbers here which we solved for

in a previous modules from the forward and the backward pass calculations.

I added to the K two other numbers that I want you to work with me in solving them.

Which is the Total Float and

the Free Float.

So that been said, the total float we have,

if you remember when I explained to you.

For all that critical activities in the critical path.

Which I highlighted here in yellow, would be zero.

Because reminding you about the equation.

The total float equal the late start minus the early start.

Or it could be the late finish minus the early finish.

So for activity A,

we have a total float of 0 minus 0 or

1 minus 1 which is equal to 0.

The same goes for activity B, also zero.

Late start minus early start for all the critical activities are the same.

The late finish and the early finish for all critical activities are the same.

Activity A, B, E, and G, so the total float for E as well is 10 minus 10, zero.

The total float for activity G is 17 minus 17 or

18 minus 18 equal also zero.

So let's go for non-critical activities and find the total float as well.

This go with activity C.

The total float will be four minus one,

or ten minus seven, which will equal to three.

And for F and D,

F would be 17 minus 11 or 13 minus seven equals 6.

And for activity D 4 minus 1 equal 3, or 17 minus 14.

So that's for the total float we have for our activities in the example here.

And we understood between the critical and the none critical activities.

So let's move forward and

try to calculate here with me the Free Float for all these activities.

And I would remind you again, the free float equation

is the minimum early start of the successors of that activity

minus the early finish of the activity.

We're trying to calculate the free float for.

In this case, also the critical activities.

We will need the same situation for the total float.

It's going to be equal to zero.

Because always the successor has an early start date.

It has to be one of the activities of the successor in the critical path

with that activity the same early start date to that same early finish date.

Let's take an example here.

Activity A, the minimum early start of the successors which will be

the early start of either one, one and one here.

So in this case, it's not that complicated.

We'll go through another example when we have different,

but the minimum to which is going to be the same.

Is going to be one.

The early start date minus the early finish date of activity A which

is also one, will give you zero here.

For B, you have only one successor.

So in this case, the early start.

For the successor is 10 minus the early finish of the activity we calculating it

is 10.

Zero activity E here not just

because it's a critical activity, but it also has only one successor.

That means the early start of the successor

is equal to the early finish of the activity which also will give you zero.

The last activity always in this case.

Would be zero, the free float form.

Now let's look for a non-critical activities and start with C here.

Activity C, the successors in this case will be activity E and activity F.

The early start for activity E is 10 and the early start for

activity F is sudden, the minimum early start will be then 7 and

you subtract 7 minus the early finish of the activity.

C which will also will give you a free float of 0.

So what about activity F and D?

Activity F has one successor which is Z,

the early start for G is 17,

the early finish of F is 11.

So 17 minus 11 which will give you six.

So the free float for activity F is six here.

And for D, the one successive also, which is G.

The early start date for activity G is 17

minus the early finish date of D which is 14,

so 17 minus 14 equal three.

So you have a free flow of activity D equals three dates.

So that's the solution for -- if I'm going to look at it,

it's a complete solution when it asks you to draw diagram

therefore a forward pass calculations to find the early start and

the early finish of all activities, perform calculations for

the backwards pass calculations to find the late start and the late finish,

and performed all the calculations for each of the activities in the diagram

to find the total float and the free float of each activity.

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