• Rules for Determining Event Times
• Rules for Determining the Critical Path
• Example Problem
• Example
• Table 2. Preceding Activities (PA)
• Table 3. Immediately Preceding Activities (IPA)

Rules for Determining Event Times

Forward Pass - Greatest number

In the forward pass through a network, the earliest time an event can occur is determined by the greatest number obtained from considering all the activities ending at that event.

Reverse Pass - Smallest number

In the reverse pass through a network, the latest time an event can occur (without changing the critical path) is determined by the smallest number obtained from considering all the activities starting at that event.

Rules for Determining the Critical Path

An activity is on the critical path if its total float is zero. Also:

Activity A, with duration D is said to be on the critical path if:

Example Problem

Note: At the beginning event and the final event, the following must be true:

Example

You are going to build a prefabricated steel warehouse according to the plans in Fig. 1 and using the activities in Table 1 below. The walls are primed, and the roof, doors, and windows are prepainted. You have the following constraints on the erection:

Front/Back Sides

Plan View(1 & 3) (2 & 4)

Figure 1 Warehouse Plans

Technical Constraints

1.Items must be assembled in the following order: footing, walls, roof, lights.

2.Doors and windows can be installed after the corresponding sides are erected.

3.Both windows must be installed at the same time.

4.Walls can be painted only after all walls are erected.

Table 1. List of Activities Required to Build a Prefabricated Steel Warehouse

Activities	Activities	Activities
Aclear and grub	Finstall wall 2	Kinstall windows 2&4
Bexcavate footing	Ginstall wall 3	Linstall roof
Crebar footing	Hinstall wall 4	Minstall lights
Dplace footing	IInstall door 1	Npaint walls
Einstall wall 1	JInstall door 3

First, we will make a list of preceding activities (PA) (see Table 2) indicating which activities must precede each given activity.

Table 2. Preceding Activities (PA)

Next, we will reduce the PA list to an immediate preceding activity (IPA) list (see Table 3).

Later, this IPA information will help us in drawing the network diagram.

Table 3. Immediately Preceding Activities (IPA)

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