Publication: Canadian Journal of Civil Engineering
11 July 2008
The activity-on-arrow (AOA) method can be used in construction projects depending on the project condition, although it is relatively inefficient as compared to the activity-on-node (AON) method. The most critical problem of the AOA method that is yet to be resolved is the application of a logical dummy activity (dummy). This
paper presents a heuristic method that can be used for systematically identifying and applying logical dummies during the creation of an AOA network based on predefined activity dependencies. The heuristic method first identifies logical dummies of one-to-one relationships, and then detects the other multiple relationships in a stepwise manner to remove the redundancies therein. La méthode de l’activité-sur-flèche (ASF) peut être utilisée selon l’état d'un projet, alors qu’elle est relativement inefficace comparée à la méthode de l’activité-sur-noeud (ASN). Le problème le plus critique qui reste à résoudre pour la méthode ASF est l'application d'une activité logique sans fonction (« dummy »). Cet article présente une méthode heuristique qui peut être utilisée pour l’identification systématique et l’application de « dummies »
logiques lors de la création d'un réseau ASF basé sur des dépendances d'activité pré-définies. La méthode heuristique identifie en premier les « dummies » logiques pour les relations de un à un, puis détecte les autres relations multiples par étape afin de supprimer les redondances.Abstract
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References
Callahan, M.T., Quackenbush, D.G., and Rowings, J.E. 1992. Construction project scheduling. McGraw-Hill, New York.
Clough, R.H., Sears, G.A., and Sears, S.K. 2000. Construction project management. 4th ed. John Wiley & Sons, New York.
Harris, R.B. 1978. Precedence and arrow networking techniques for construction. John Wiley & Sons, New York.
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KyunghwanKimK. Kim. Identifying logical dummy activities in an activity-on-arrow network. Canadian Journal of Civil Engineering. 35(7): 739-743. //doi.org/10.1139/L08-007
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Which system of network given below completely eliminates the use of dummy activities?
- A – O – A (Activity – on - Arrow)
- A – O – N (Activity – on - Node)
- PERT
- CPM
Answer (Detailed Solution Below)
Option 2 : A – O – N (Activity – on - Node)
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Concepts:
Dummy Activity: A dummy is a type of activity which neither requires time nor any resource, but it denotes dependency among the activities. It brings logical correctness in a network diagram and represented by dashed arrow in network diagram.
A–O–A (Activity-on-Arrow) Network: In this kind of network system, activities are represented by arrows and events are represented by the nodes connecting the arrows at starting and ending. In A-O-A system to establish interdependency dummy activities are frequently used. A diagram of A-O-A system shown below:
As, CPM and PERT are two different types of A-O-A network system, so in CPM and PERT also there are frequent use of dummy activity.
A–O–N (Activity-on-Node) Network: In this kind of network system, activities are represented by nodes and arrows shows the immediate predecessor activity. In A-O-N system there is no need of dummy activity because activities are represented by nodes and their interdependency can be directly denoted by properly connected arrows. A diagram of A-O-N system shown below:
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