Ladders

Machine

Hand

Level

Machine

Hand

Level

Stage II

Stage II

Figure 20.23

Figure 20.23

Machine

Hand

Level

Machine

Hand

Level

Stage II

Stage II

Stage III

Machine

Oexc.

Stage II

Stage III

Hand trim

'Marhine

Level bottom

I Hand

I level

Hand trim

'Marhine

Level bottom

I Hand

I level

Blind

Blind

Machine Hand Level *

Machine Hand Level *

Figure 20.25

Blind

Blind

Machine Hand Level

Oexc. trim bottom Blind

Figure 20.26

This concept led to the development of a new type of network presentation called the 'Lester' diagram, which is described more fully in Chapter 23. This has considerable advantages over the conventional arrow diagram and the precedence diagram, also described later.

Once the network has been numbered and the times or durations added, it must be analysed. This means that the earliest starting and completion dates must be ascertained and the floats or 'spare times' calculated. There are three main types of analysis:

1 Arithmetical;

2 Graphical;

3 Computer.

Buy

3

Clear

land

land

2

Delay

2

Dig trench 6

Lay cable 4

After 3

Strip 6

Paint 7

2 '

2

Skip deliv

Fill

Figure 20.27 Dependencies

Dig trench 3

Dig trench 3

Lay cable 3

Lay cable 1

Day 2

Figure 20.28 Alternative configurations

Day 2

Figure 20.28 Alternative configurations

Since these three different methods (although obviously giving the same answers) require very different approaches, a separate section has been devoted to each technique (see Chapter 21).

By far the most common logical constraint of a network is as given in the examples on the previous pages, i.e. 'Finish to Start' or activity B can only start when activity A is complete. However, it is possible to configure other restraints. These are: Start to Start, Finish to Finish and Start to Finish. Figure 20.27 shows these less usual constraints which are sometimes used when a lag occurs between the activities. Analysing a network manually with such restraints can be very confusing and should there be a lag or delay between any two activities, it is better to show this delay as just another activity. In fact all these three less usual constraints can be redrawn in the more conventional Finish to Start mode as shown in Figure 20.28.

When an activity can start before the previous one has been completed, i.e. when there is an overlap, it is known as lead.

Project Management Made Easy

Project Management Made Easy

What you need to know about… Project Management Made Easy! Project management consists of more than just a large building project and can encompass small projects as well. No matter what the size of your project, you need to have some sort of project management. How you manage your project has everything to do with its outcome.

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