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.

从本节课中

Understanding Work Dates and Calendar Dates

In this module, the difference between working dates and calendar dates is explained and how to chart both in a project plan.

Instructor, Department of Civil Engineering and Engineering Mechanics, Columbia University Director of Research and Founder, Global Leaders in Construction Management

Let's say that the project on this

calendar here has the following

activity on node diagram.

We covered activity on nodes.

We covered activity on arrows.

We covered bar charts or Gantt charts.

And we're going to highlight only activity or node for simplicity to

understand the concepts between the work day and the calendar date.

So, I took the same exact calendar that I just showed in the previous slide.

And I linked it also to a project, simple one.

It could be a subcontractor that's working for a general contractor for

short assignment if the project were full days of work.

So, we notice from the activity or node here,

that the project starts with the activity A,

and goes into just two routes, either A and

then C and then E or A, B, D and E.

If you notice with the four numbers I put around each node,

from what we recall from the forward and the backward past calculations.

We identified the early start of each

activity and the early finish and

the late start and the late finish.

And that goes for the entire project.

And if you notice, because we have two paths here,

it is not required but I want to refresh your memory.

What would be the critical path here?

It would be the longest duration from the two paths.

It's going to be A, B,

D, and E and not A, C, and E.

2,4 and 2.

You have 8 days, 2, 3, 5, 2, you have 12 days.

So that's the critical path.

As you notice, also the early start and

the late start are equal from all the critical activities.

And the early finish, late finish are also equal for all the critical activities.

Now, I will ask you to try,

to find the early start and the early finish.

As well as the late start and the late finish for

all the activities in the project here.

But, from a calendar date's point of a view.

Before we move forward with the calculations,

let me refresh your memory also for something more important here.

If you remember, when we cover the forward and

the backward task calculations,

we came up with of course these durations.

So let's say, for example,

of the early start date of activity D would be 5.

That 5 which refer to in this project as working day number 5.

In this example, that means, we need to wait for

activity A and, which is 2 working days,

and activity B, which is 3 working days.

So we are waiting a total of 5

working days, 2 for A, 3 for B.

So as in the beginning of working days 6.

So when the 5th day finishes,

the beginning of the work day number 6,

that will be activity D will start.

So we finish the 5 working days done.

Working day number 5, that's mean starting of day number 6 or working day number 6.

So, on calendar dates here,

the start of activity D will be on working

day number 6, which will be here,

working day number 6, is December, 30th.

So we finish let's say, for example, here, activity A, 1, and 2.

And then activity B, 1, 2, and 3.

And then activity D, it's going to start here.

So the way I would do it here in the following example,

I would look at the early start day or

the latest start date as well.

So either the early or the late start days of any activity,

not just critical of course.

Any activities in the project.

For example here, we are talking about activity D.

I take its earliest start which is 5,

I added to it 1.

Then it will give me working day number 6.

And that will be on the calendar date as the early start date for that activity.

So drop up activity D,

the early start date from a calendar

date would be 5 plus 1,6.

The work day number 6, so it would be December, 30th.

And where we're going, details about all of the activities in the following slide.

But, now, this 1 day shift will apply

to all activities, as I mentioned,

including their late start dates as well.

However, for the early finish dates and

the late finish dates of the construction activities,

we do not apply that 1 shift day.

We just directly connect or

relate that working days at the calendar dates here.

With that early finish and the late finish of each activity in the project.

So in this case, we can say that, let's say,

the early finish day for

also activity D will be in working day number 10.

So, in calendar dates it would be Wednesday, January 6.