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Published byAlex Pittman Modified over 2 years ago

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Prosjektstyring We have a project with three activities: planning, purchase and construction. Each of the activities has a duration of 10 weeks. This means that if we add the durations, the total duration of the project becomes 30 weeks. We can also assume, for this example, that the activities can overlap with each other. Purchase can start 2 weeks after planning starts. We can also assume that purchase should finish two weeks after planning has finished. We have now introduced two types of links between purchase and planning Planning (10) 3 Purchase (10) 4 Construction (10)

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Prosjektstyring Planning (10) Purchase (10) SS2 FF2 Construction (10) SS2 FF2 We have shown, with an SS (start to start) dependency and a lag time of 2 weeks, that the start point for purchase is linked to the start of planning with a lag time of 2 weeks. We also introduced an FF (finish to finish) dependency when we said that purchase should finish two weeks after planning has finished. This means that the finish of planning is linked to the end of the purchase activity with a lag of 2 weeks. We assume the same relationship between purchase and construction. Construction can start when purchase has been going on for two weeks, and construction must finish 2 weeks after purchase has finished. We now have two similar links between purchase and construction and between planning and purchase.

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Prosjektstyring Planning (10) Purchase (10) SS2 FF2 Construction (10) SS2 FF2 We have set up the activities in an AON network and calculated the duration of the project. Planning starts in week zero. This is also the earliest start date for the activity. The earliest finish is found by adding the earliest start value to duration of the activity. Planning has a duration of 10 weeks, which gives us an earliest finish of = 10 Purchase: = 12 Construction: = 14 After two weeks, purchase starts. We have an earliest start time of 2 for purchase. Construction can begin two weeks later, so the earliest start point for construction is week 4.

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Prosjektstyring Planning (10) 102 Purchase (10) 12 SS2 FF2 4 Construction (10) 14 SS2 FF2 We can also calculate the latest times for the activities. We start with the projects finish time and assume that the earliest finish is equal to the latest finish. To find the latest start point, the duration of the activities is subtracted. Construction: = 4 By allowing overlap between the activities, we have reduced the projects duration from 30 to 14 weeks. Purchase: = 2 Planning: = 0

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Prosjektstyring We can draw a precedence network with the information from the AOA network. Wil will divide the activities into three parts: a start part, a middle part and a finish part. Planning has a start part with duration of 2 weeks. After these two weeks have elapsed, the start part of purchase begins. Planning will be fully accomplished in week 10. We can see that the purchase activity is split here, and that the remaining part is the finish part, which lasts for 2 weeks. When purchase has been going on for two weeks, the start part of construction can begin. Again, there is a 2-week finish part for construction starting from the time purchase is finished. Now we have a precedence network in the form of a usual CPM-AOA network.

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