Backward Pass Calculations

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Do curso por Columbia University

Construction Scheduling

739 classificações

Columbia University

Construction Scheduling

739 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.

Na lição

Activity on Arrow

Activity on Arrow diagrams are the topic for this module. Professor Odeh will discuss how to draw an activity on arrow diagram and how to number the nodes. Forward and Backward Pass calculations and determining the duration of a project are also covered.

Introduction to Activity on Arrow11:35

Drawing an Activity on Arrow Diagram6:37

Numbering Nodes on a Diagram2:00

Practice Drawing Activity on Arrow Diagrams4:53

Advanced Activity Diagrams14:40

Adding a Key to An Activity on Arrow Diagram17:25

Backward Pass Calculations6:38

Determining the Duration of a Project8:32

Conheça os instrutores

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

Now let's go through a backward pass calculations.

And we'll go one by one, similar to the backward

pass calculations that we did for the activity on node.

We do start with the last one and move backward.

So we can have either the arrow here or here.

So this is then day 15.

And then, the late start date for

the predecessors after this 15 would be the same thing.

So here, you have 15, here, we have 15, and here, we have 15.

So that being said, then the late start of an activity

will be the late finish minus the duration.

So for J, would be 15 minus 1 equal 14.

For K, 15 minus 2 equal 13.

For I, 15 minus 13 equal 12.

As all the lead start dates for these activities.

So let's go towards the node number 9.

With node number 9, we take 14 in this time,

towards this node here,

which will go towards the predecessors of D and

this dummy activity, which will go towards this node.

So we have 14 here, 14 in this dummy activity, and 14 here.

So once we have a node that has two activities coming,

in this case, for node 8, coming J, and coming K.

So that latest for node 8 would be

the minimum between the 14 and

the 13, which will be 13.

And the 13 on node 8 will

be equivalent to the late start dates for H.

And this is a dummy activity would be also 13,

13, 13, which will be also for G13.

And the late start dates for G and

H will be 13 minus 5 equal to 8 here.

And for H, 13 minus 3 equal to 10 here.

So that node in time then will be in the backward pass calculations.

The minimum between 8 or 10 which will equal to 8,

And the 8 will be the late start of activity E,

8 minus 4, that I'm sorry, late finish.

And the late start for E would be 8 minus 4 equal to 4.

Because this is a dummy activity, we have 8 and 8 here.

That will leave us to go to node number 6 down there.

12, we can take it also as 12 here,

Which will leave us to late finish 12, late start 12,

because it's a dummy activity for F.

Late finish, 12.

The late start, 12 minus 3 is 9.

Because this is the only activity coming,

the node time here is 9 in the backward pass calculations.

And for node 3 here,

we have the minimum between 8 and

12, which will be an 8 and

we can have it above here.

Which the late finish day for B would be also 8 in this case.

8 minus 2 equal 6, which will be the late

start date for B, so what we missing here?

Node 2 here, which we highlighted from D and E.

D will be 14 minus 14 late start, late finish date for D minus 4.

Late start date for D is 10, the minimum between 4 and

10 also equal 4,

which will have the late finish 4, the late start, 1 for activity A.

Then will leave us with 9 as a late start for C.

9 minus 1 is 8.

The minimum for activity 1 between 1, 6,

8, which will be, 1 here.

So that is the calculations that I did by

hand to identify all the early start,

early finish, late start and

late finish of all the activities.

And what's the point in time that we can reach that node and

the latest point in time we reach that node.

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