Basics in Building Construction

Basics in Building Construction 4(2+2)

Lesson 31 and 32 : Construction Project Management

Elements Of Network

Before describing the method of developing a network, it is necessary to understand the terms used in network techniques.

1. Network:The network is a graphic plan showing jobs or activities that must be completed to achieve completion of a project. A network is also defined as an arrow diagram obtained by connecting all the activities of project in logical sequence. Thus the components which make up a network are activities and events.


2. Activity: The jobs that are required to be performed in executing a project are known as Activities. The tail of the arrow represents start of the activity and head arrow represents the completion of the activity. The head of the arrow shows direction of time flow from one event to another. In a network the activities are arranged in a logical sequence of their occurrence. Thus it may be seen that activity represent performance of work and it consumes time and resources.


3. Event: An event represents specific definable accomplishment in a work plan. In other words, this is a point in time representing start or completion or one or more activities. An event is generally represented on a network by geometrical symbol such as ; circle or rectangle and is identified by code numbers like 1,2,3 etc. An event consumes neither time nor resources. It is a point in time and not passage of time.

The concept of event and activities are explained in the following figure. In the figure the activities are designated by 1-2-6(B) etc. The activities are arranged in their logical sequence. From the review of diagram, it can be seen that activity –A controls activity B, C, D and E. Alternatively it can be said that activity B, C, D and E depend on activity –A. The examples of events in the above Figure are event no.1 shows start of the work A. Event no.2 represents the completion of the work A and also represents start of activity B.

4. Dummy activity: It is a notional activity which neither consumes time nor resources but indicates the logical sequential relationship between other activities. Dummy activities are therefore introduced to represent a connection or inter dependency between events. Dummy activities are represented on a network by a dotted arrow.