Introducing Bar (Gantt) Charts

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Construction Scheduling

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Columbia University

Construction Scheduling

681 classificações

Curso 2 de 4 em 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.

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Bar (Gantt) Charts

The second module introduces bar or Gantt charts and how they are used as scheduling tools. Bar charts represent a project work item or activity as a time scaled bar; the length of which represents the planned duration of a construction activity.

Introducing Bar (Gantt) Charts10:56

Using Bar (Gantt) Charts8:46

Advantages and Disadvantages of Using Bar (Gantt) Charts8:30

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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

Hello, everyone.

I will be talking in this module about a specific scheduling tool,

which is the bar charts, or sometimes we refer to as the Gantt chart.

Basically, the Gantt charts, or the bar charts, was originally developed by Mr.

Henry L Gantt in 1917.

And the bar charts acts as both a planning and

scheduling tool, as well as a reporting or

a control tool in your construction projects.

So with the focus of the class of this course, we'll be talking

more that scheduling part of the bar charts and some of the planning.

It's a basic scheduling tool.

The concept is basically that the bar chart is focusing on representing

any kind of a project construction activity or

a group of construction activities as a time scaled bar.

Which the length of the bar represents the planned duration of

that specific construction activity or group of activities.

If we want to give an example of a bar chart,

usually we have two of a y and a x axis.

And the common utilization of using bar charts is the uses of the x axis more,

and the x axis refers to the project time scale.

That could be in days or in weeks or even in months.

Sometimes in a rare situation if the project is really big or

we have a program of multi years going on the road, then we have in years as well.

Basically, the bar chart we highlight it as a rectangle as you can see here,

look like a bar.

And that refers to a specific work item or

a construction activity or a task to be done in that project.

The length of the bar refers to the planned duration that it will

take that work activity or construction activity to be done or accomplished.

If we have, for example here, four points or

segments, these segments could be days or

could be weeks or months.

So that specific construction activity can finish in four days, for

example, or four weeks.

That help us actually further in finding how the percentage,

or how much completed from a percentage point of

a view if we shade a specific component or specific part of the bar.

For example, if we know this is a four months construction activity and

we highlighted or shaded the first quarter,

that will simply tell us that we finished 25% of the work of that specific item.

If we have 50% shaded,

that mean we completing 50% of the work and so on from 75.

And if we have shading all the bar here at that specific work item,

that tell us that the team are finished with that construction activity.

That being said, let's go through an example.

So if we have a very simple project of

three construction activities,

activity A, activity B, activity C,

as I told you the X axis refers to the time scale.

So let's go one by one.

Activity A, it starts the first activity in the project and

finishes or the duration of activity A from what we can see here is 4 months.

Activity B also starts after we finish the first month of the project,

as we can see here, and lasts also around four months and

finish in month number 5 of the total duration of the project.

The last activity, activity C,

starts at the end of month number 2, and

only takes one month to finish.

What I said before, by using differentiating patterns or

colors, the bar chart or the Gantt chart can indicate monthly

progress toward physical completion of the construction

activities or the entire project in general.

So let's go through an example.

If we say that I'm going to shade in yellow

color that the work completed at end

of month 2, and I gave you this.

So the interpretation for this kind of example,

it tell us, let's go one by one,

construction activity A at the end of month 2,

40% of that activity been finished.

The question for you, what supposed to happen?

What's the planned for such a scheduling tool we have or

planning tool we have at end of month 2, activity A,

how long it's supposed to finish?

If we look here, we are planning at end of month 2 to

finish around 50% of activity A.

And we are finishing only 40% because the duration of activity A is four months.

The first two months you're finishing the first 50, or the half, of that activity.

We are behind the schedule at end of month 2 for

the first activity, activity A, by 10%.

What about activity B now?

Activity B at end of month 2,

we mentioning that we finish around 10% of the work.

But in matter of fact, the planning tool we have in this bar

chart to finish around 25% in month 2 before we start month 2.

Because we have activity B, four months and

the first month, 1 over 4, 25%, so

we are also behind the schedule on activity B around 15%.

We're suppose to finish 25, but we finish only 10.

So what if I told you I'm going to shade

in red color the work completed in this

project at end of month 3 by the following.

So let's go an activity by activity.

Activity A, in this case, finished another 30% in that extra month.

The plan was to finish at

the end of month 3 around

75% of activity A.

So in this case, are we behind or ahead of schedule?

We are also behind schedule around 5% in that specific construction activity.

We supposed to finish 75% at end of month 3.

And we finished only 70%,

40 as the first two months,

30 at the end of month 3.

How about activity B?

Are we ahead or behind the schedule at the end of month 3?

At the end of month, I'm sorry.

Before we end month 3, we suppose to finish 50%.

So we have all one, two months, and we have another two

months to finish activity B, so we have 50%.

And we already finished 10% plus 40%, 50%, and

we have another 50% left for activity B.

So we are on time, not ahead of schedule or not behind of schedule.

We are on time for that activity.

What about activity C?

Work completed for activity C at

end of month 3 is 70%, but

the plan to finish all activity C by end of month 3.

That being said, we are behind the schedule for activity C.

In this case, if I ask you what left in each of the construction activities

that need to be done, we can easily tell that in activity A, we have

30% left to be done towards the end of the project until we accomplish that activity.

For activity B, we have also another 50% that

we need to accomplish or perform or finish to finish activity B.

For activity C also we have another 30% need to be done to finish with activity C.

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