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Floats in the AoA network. Project management ( lecture ). Activity and event times. Activity times: EST LST EFT LFT Event times: EET LET. Float. Time available for an activity or path in addition to its duration. It can be positive or negative
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Floats in the AoA network Project management (lecture)
Activity and event times • Activity times: • EST • LST • EFT • LFT • Event times: • EET • LET
Float • Time available for an activity or path in addition to its duration. • It can be positive or negative • It is a property of activities (and available only at given activities) • In case of more succeeding activities, the minimum have to be taken. • Types of float: • Total float • Free float
Total float ? 0 ? ? 3 4 1 2 • The total float possessed by an activity. • Calculation for activity j: Total floatj = LFTj – EFTj • Identify the activity possessing float below, and calculate the total float. ? 35 ? ? 10 12 c a 15 8 b d
Total float • The total float possessed by an activity. • Calculation for activity j: Total floatj = LFTj – EFTj = LFTj – (ESTj + Dj) • Identify the activities possessing float below, and calculate the total float for each. Total float = = 11 – (0+5) = 6 Total float = 23 – (5+12) = 6 5 2 12 5 11 c a 0 23 1 4 15 8 0 23 b 15 d 3 15
Calculating free float • The float possessed by an activity which, if used, will not change the float in leater activities. • Free floatj = ESTj+1 – EFTj = EEThead – EETtail - D Free float = = 5 – 0 – 5 = 0 Free float = 23 – 5 – 12 = 6 5 2 12 5 11 c a 0 23 1 4 15 8 0 23 b 15 d 3 15
Negative float 0 ? ? 1 2 3 • If the target time (deadline) for the project (or for a part of the project) is grater than TPT, than the float will appear on the critical path or even on some other paths. • Negative float = the time by which activities on the path or paths concerned must be reduced if the TPT is to be met. • Negative float is a type of the Total Float. ? ? ? 30 10 10 a c
Negative float 0 10 20 1 2 3 • If the tartget time (deadline) for the project (or for a part of the project) is grater than TPT, than the float will appear on the critical path or even on some other paths. • Nagative float = the time by which activities on the path or paths concerned must be reduced if the TPT is to be met. • Negative float is a type of the Total Float. 15 -5 5 15 10 10 a c Total float: -5 Total float: -5
Slack • Refers to events and not to activities. • Slack = LET - EET Slack: 6 Total float = = 11 – (0+5) = 6 Total float = 23 – (5+12) = 6 5 2 12 5 11 c a 0 23 1 4 15 8 0 23 b 15 d 3 Slack: 0 Slack: 0 15 Slack: 0
Readings • Lockyer – Gordon (2005) Chapter 13
7 2 10 7 11 c a 0 23 1 4 15 8 0 23 b 15 d 3 15