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Project activities relationships

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project activities are related to each other, different relationship link project activities, knowing the type of relationship of activities will assist the project team in providing efficient plans and properly utilizing available manpower and equipment, knowing the type of relationship required good experience for a similar type of work, as engineers we need to answer following question for each activity:
  • what activities should finish before proceeding with this activity?
  • what activities should be executed at the same time with this activity?
  • what activities should begin after the completion of this activity?   




Let take an example of casting a building slab, concreting of building slab cant be done if we didn't place the reinforcement, similarly reinforcement cant be placed if we didn't install formwork and so on,  our activity is slab casting, before casting of slab we should finish slab reinforcement, for slab reinforcement to begin we should install formwork, installation of formwork will be followed by placing slab reinforcement and so on.

 another example: Suppose that site preparation and concrete slab foundation construction project consists of nine different activities:

 A. Site clearing (of brush and minor debris),
B. Removal of trees,
C. General excavation,
D. Grading general area,
E. Excavation for utility trenches,
F. Placing formwork and reinforcement for concrete,
G. Installing sewer lines,
H. Installing other utilities,
I. Pouring concrete.

 in this example site clearing and removal of trees can be done at the same time as they don't interfere with each other, for general excavation and grading to start we should finish site clearing and if in the discretion of the planner the removal of trees will affect those activities then tree removal will precedent them. determining the predecessors of activities should be done by a competent engineer, the engineer should have sufficient experience to know the steps of work and the place of each activity, inexperienced will not be able to determine the accurate path of project activities.
Table 1










Types of activities relationships
we have four types of activities relationships:

  • Finish to start(FS): the successor relationship will only start after the completion of the current activity.
 

  • Finish to Finish(FF): the finish of successor activity depends on the finish of the current activity. an example of this activity is laying of asphalt for a road of 10 km, if 2 km of asphalt laid per day and the road marking done for this 2 km, the completion of road marking will require the laying of all asphalt.

  • Start to start(SS): The start of the successor activity depends on the starting of the current activity. an example of this is the laying of asphalt for a long road, laying of asphalt will be done on several days and this start for first portion cant begin before beginning the laying of previous layers.

  • Start to finish(SF): The successor activity can't finish until the current activity start. One example is the start of the new shift of the security guard signal the finish shift of the current security guard.

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