Critical path analysis

A precedence diagram represents the activities as a rectangle including details of activity the start, finish and duration of the activity.

Figure 8: Precedence diagram format

The various programming software may illustrate the activities and information slightly differently however. In figure 8, the activity duration is indicated in the centre of the activity box; the early and late start times are to the left and the early and late finish times to the right.

Once the scope of the project has been considered and the individual activities have been defined they can be linked together using this logic and durations can be assigned to form a network.

When entering the activity details, dependent on the software used, other activity information can be entered including the assignment of specific calendars, required resources and coding.

Figure 9 Network for simple substructure works

Figure 9 represents a small network for typical substructure works, with activities linked together by logical constraints of the type previously described and the estimated activity durations shown in numbers of days.

Lead and lag times have also been added, and it can be seen, for example that the piling works, Activity C cannot be finished until 2 days after the existing slabs have been broken out, Activity G.