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A Project: Duration 21 days, Total Cost $400. AoA to use it almost like a Gantt Chart. c. f. a. d. g. b. e. Total Cost 400 Duration 21. 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21.
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A Project: Duration 21 days, Total Cost $400 AoA to use it almost like a Gantt Chart c f a d g b e Total Cost 400 Duration 21 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Ardavan Asef-Vaziri 6_Ex2-1
From 21 Day To 20 c f d g a 400+30 = 430 a b e Total Cost 430 Duration 20 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 10/12/2014 Ardavan Asef-Vaziri 6_Ex2-2
Crashing to 20 Days Activities a,c, & f are on the critical path a is the least-cost choice, therefore we crash a Lower a’s normal time by one day It now equals the crash time and cannot be shortened further The critical path is unchanged The critical time has been lowered to 20 days The cost of the project is $400+30(a)= $430 10/12/2014 Ardavan Asef-Vaziri 6_Ex2-3
From 20 Day To 19 1 f 430 +40 = 470 c f a d g b e But instead of 21 to 20 to 19 We could also have 21 to 19 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Ardavan Asef-Vaziri 6_Ex2-4
Crashing- 19 Days a is available for crashing and f costs $40/day to crash, which is the next lowest cost for path a-c-f. Rather than crashing a and f at a cost of $70, we could crash c alone. Duration of a-c-f is cut by two days for an incremental cost of $60. Except, not crashing a means that no matter what we do with other activities on a-c-f, the a-d-g path which requires 20 days will limit us to a one-day improvement. Unless we also crash g at cost of 60 Crash a and f for one day each Project duration lowered to 19 days Cost is $400+30(a)+40(f)= $470 10/12/2014 Ardavan Asef-Vaziri 6_Ex2-5
From 21 Day to 19 by Crashing C Reverse a, crash c by 2, also crash g c2,g 60+60 = 120 a, f 30+40 = 70 c f a d g b e Total Cost 470 Duration 19 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Ardavan Asef-Vaziri 6_Ex2-6
From 19 Day To 18 All paths Critical 1 a and d cannot crash Crash g for adg and beg 1 Crash f for acf a then f to 19 then g and f 40+60 = 100 470+100 = 570 c f a d g b e 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Ardavan Asef-Vaziri 6_Ex2-7
From 20 Day To 18 by Crashing c a +30 1 c2 and g - f a to 20, f to 19, then g and f (30) + (40 + 40+60) = 30 +140 a to 20, then c2 and g (30) +(60+60) = 30+120 120 <140 c f c f a d g g b e Total Cost 430+120 =550 Duration 18 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Ardavan Asef-Vaziri 6_Ex2-8
Crashing- 18 Days We now have two additional critical paths. If project duration is to be shortened, all paths must be shortened. g is the only element of paths a-d-g and b-e-g) that can be crashed so we cut g by one day at an incremental cost of $60. f could be shortened by another day at a cost of $40, but crashing f by two days raises the project cost by $80. It is less expensive not to crash f, but to crash c instead. The project duration is now 18 days Cost is $400+30(a)+60(c)+60(g)= $550 10/12/2014 Ardavan Asef-Vaziri 6_Ex2-9
From 18 Day To 17 1 2 1 c f a d g f and g 40+60 b e 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Total cost = 550+100 = 650 Ardavan Asef-Vaziri 6_Ex2-10
From 17 Day To 16 1 2 1 2 c f a d g f and g 100 b e 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Total cost = 650+100 = 750 Ardavan Asef-Vaziri 6_Ex2-11
Crashing- 17,16 Days We can shorten the project to 17 days by crashing both f and g one more day, and to 16 days by crashing them still another day. Activities a,c,f, and g have been crashed to their limits. No further crashing will help so b,d, and e remain at their normal times and costs. The total project cost of the 16-day project is 50(b)+30(d)+70(e)+90(a)+160(c)+120(f)+230(g) = $750 10/12/2014 Ardavan Asef-Vaziri 6_Ex2-12
Project Cost Versus Project Duration for Sample Just Shown Crash Problem 10/12/2014 ArdavanAsef-Vaziri 6_Ex2-13