NETWORK, CPM DAN PERT. Dr. Mohammad Abdul Mukhyi, SE., MM

Transkripsi

1 NETWORK, CPM DAN PERT Dr. Mohammad Abdul Mukhyi, SE., MM 1

2 PENDAHULUAN Hal penting dalam manajemen proyek adalah : Ketepatan memilih bentuk organisasi (tim) Memilih manajer proyek yang tepat Aktifitas integrasi idan koordinasi i yang baik Diluar hal tsb diperlukan : Apa yang akan dikerjakan Bagaimana pengendaliannya? 2

3 LINGKUP PEKERJAAN Perencanaan dan pengendalian : Sebelum proyek dimulai Selama proyek berlangsung Koreksi pada saat terjadi perbedaan antara rencana dan pelaksanaan Ditujukan untuk mengurangi ketidakpastian tentang apa yang akan dihasilkanilk dari pengerjaan proyek 3

4 ALAT ALAT PERENCANAAN Banyak metoda yang digunakan dalam perencanaan antara lain: Work breakdown structure (WBS) untuk menentukan pekerjaan pekerjaan yang ada dalam proyek. Matriks tanggungjawab untuk menentukan organisasi proyek, orang orang kunci dan tanggungjawabnya. Gantt charts digunakan untuk menunjukkan jadwal induk proyek, dan jadwal pekerjaan secara detail. Jaringan kerja (network) untuk memperlihatkan urutan pekerjaan, kapan dimuiai, kapan selesai, kapan proyek secara keseluruhan selesai. 4

5 PENDEFINISIAN PEKERJAAN Utk proyek dalam skala besar diperlukan metode untuk menentukan elemen elemen proyek dalam bagian yang lebih detail. Dapat diketahui keterkaian antar aktifitas, urutan waktu dan personilnya. Work Breakdown Structure (WBS) Manfaat dari WBS : Dalam tahap analisis WBS dapat digunakan untuk memastikan akurasi dan kelengkapan dari semua personil proyek Dijadikan sebagai dasar penganggaran dan penjadwalan Sebagai alat kontrol pelaksanaan proyek 5

6 PROYEK Suatu proyek adalah suatu usaha temporer yang menyertakan suatu urutan aktivitas yang dihubungkan dengan sumber daya, yang dirancang untuk mencapai suatu hasil yang unik dan spesifik dan yang beroperasi di dalam waktu, biaya dan batasan mutu dan sering digunakan untuk memperkenalkan perubahan. 6

7 CHARACTERISTIC OF A PROJECT A unique, one-time operational activity or effort Requires the completion of a large number of interrelated activities Established to achieve specific objective Resources, such as time and/or money, are limited Typically has its own management structure t Need leadership 7

8 APA PROYEK MANAJEMEN? Aplikasi dari suatu koleksi teknik dan perkakas untuk mengarahkan penggunaan sumber daya yang berbeda ke arah pemenuhan dari suatu yang unik, kompleks, waktu, biaya dan batasan mutu. Perang dunia II, manakala otoritas militer menggunakan teknik operasional research untuk merencanakan jumlah maksimum penggunaan sumber daya. Salah satu teknik ini adalah penggunaan jaringan untuk menghadirkan suatu sistem dari aktivitas terkait 8

9 PROJECT MANAGEMENT PROCESS Project planning Project scheduling Project control Project team made up of individuals from various areas and departments within a company Matrix organization a team structure with members from functional areas, depending on skills required Project Manager most important member of project team Scope statement a document that provides an understanding, justification, and expected result of a project Statement of work written description of objectives of a project Organizational Breakdown Structure a chart that shows which organizational units are responsible for work items Responsibility Assignment Matrix shows who is responsible for work in a project 9

10 Work Breakdown Structure for Computer Order Processing System Project 10

11 PROJECT PLANNING Resource Availability and/or Limits Due date, late penalties, early completion incentives Budget Activity Information Identify all required activities Estimate the resources required (time) to complete each activity it Immediate predecessor(s) to each activity needed to create interrelationships 11

12 PROJECT SCHEDULING AND CONTROL TECHNIQUES Gantt Chart Critical Path Method (CPM) Program Evaluation and Review Technique (PERT) 12

13 Gantt Chart Graph or bar chart with a bar for each project activity that shows passage of time Provides visual display of project schedule 13

14 NETWORK Untuk perencanaan. Hubungan antara komponen dalam network dan elemen dalam masalah riil -Penerapan model network: Masalah transportasi Masalah prosesing Perencanaan dan pengendalian proyek penugasan 14

15 Masalah Transportasi: PABRIK A 1 A 2 A = suplly 3 TEMPAT B B B PEMASARAN = demand 15

16 BIAYA TRANSPORTASI DAN DISTRIBUSI BARANG Tempat pemasaran pabrik M Jumlah persediaan 1 C 11 X 11 C 12 X 12 C 13 X 13. C 1M X 1M S 1 2 C 21 X 21 C 22 X 22 C 23 X 23. C 2M X 2M S 2 : : 3 : : : : : :. : : : : N C N1 X N1 C N2 X N2 C N3 X N3. C NM X NM S N Jumlah permintaan D 1 D 2 D 3. D M ΣD J ΣS J 16

17 Formulasi model transportasi Min : Sk. n m X C X n m ij ij i = 1 j = 1 Min : CijXij m i = 1 j = 1 j = 1 m j = 1 X ij X ij ij D S j i dimana i = 1, 2, 3..., m Sk. dimana j = 1, 2, 3..., n 0 dimana i dan j m j = 1 m j = 1 X ij Xij = D dimana i = 1, 2, 3..., m X ij = S j i dimana j = 1, 2, 3..., n 0 dimana i dan j 17

18 Masalah Transhipment Untuk menentukan jumlah dan lokasi titik angkutan serta berguna untuk menentukan jumlah dan lokasi titik angkutan secara optimal dengan meminimalkan biaya angkutan antar lokasi. 18

19 + 1 truk 3 C 36 C 23 C34 C 12 C C 46 C truk 0 truk C 54-3 truk - 4 truk C truk C 56 19

20 Lokasi Rute Pengiriman X 12 X 23 X 24 X 25 X 34 X 36 X 54 X 56 X 63 X 67 Kapasi tas Barang

21 Fungsi Linear Programing Min :C sk : X 12 - X X 12 + X - X - X - X - X + C X + X X + X - X C + X + X 46 + X X - X 24 + X - X X ij 0 untuk semua i dan j X X C 25 + X X C 34 X 34 + C 36 X 36 + C 46 X 46 = 8 = - 0 = 1 = - 2 = 0 = -3 = 4 + C 54 X 54 + C 56 X 56 + C 67 X 67 21

22 HISTORY OF CPM/PERT Critical Path Method (CPM) E I Du Pont de Nemours & Co. (1957) for construction of new chemical plant and maintenance shut-down Deterministic task times Activity-on-node node network construction Repetitive nature of jobs Project Evaluation and Review Technique (PERT) U S Navy (1958) for the POLARIS missile program Multiple task time estimates (probabilistic nature) Activity-on-arrow network construction Non-repetitive jobs (R & D work) 22

23 TEKNIK CPM Pekerjaan-pekerjaan j dalam proyek harus menandai saat berakhirnya proyek. Pekerjaan-pekerjaan j dapat dimulai, diakhiri dan dilaksanakan secara terpisah dalam suatu rangkaian tertentu. Pekerjaan-pekerjaan dapat diatur menurut suatu rangkaian tertentu. 23

24 ATURAN Setiap aktivitas ditujukan dengan suatu cabang tertentu, cabang ini menunjukkan saat dimulainya dan diakhirinya suatu kejadian. Antara suatu cabang dengan cabang lainnya hanya menunjukkan hubungan antar aktivitas atau pekerjaan yang berbeda. Bila sejumlah aktivitas tasberakhir pada suatu kejadian, a maka aini berarti bahwa kejadian ini tidak dapat dimulai sebelum aktivitas yang berakhir pada kejadian ini selesai. Aktivitas dummy digunakan untuk menggabungkan dua buah kejadian, bila antara suatu kejadian dan kejadian yang mendahuluinya tidak dihubungkan dengan suatu aktivitas tertentu. Aktivitas dummy ini tidak mempunyai biaya dan waktu. Setiap kejadian diberikan tanda angka, sedang setiap aktivitas diberikan tanda angka menurut kejadian awal dan kejadian yang mengakhiri. 24

25 PROJECT NETWORK Network analysis is the general name given to certain specific techniques which can be used for the planning, management and control of projects Use of nodes and arrows Arrows An arrow leads from tail to head directionally Indicate ACTIVITY, a time consuming effort that is required to perform a part of the work. Nodes n A node is represented by a circle - Indicate EVENT, a point in time where one or more activities start and/or finish. Activity A task or a certain amount of work required in the project Requires time to complete Represented by an arrow Dummy Activity Indicates only precedence relationships Does not require any time of effort 25

26 Event Project Network Signals the beginning or ending of an activity Designates a point in time Represented by a circle (node) Network Shows the sequential relationships among activities using nodes and arrows Activity-on-node (AON) nodes represent activities, and arrows show precedence relationships Activity-on-arrow (AOA) arrows represent activities and nodes are events for points in time 26

27 AOA PROJECT NETWORK FOR HOUSE Lay foundation 3 Dummy Build house Finish work Design house and obtain financing Order and receive materials Select paint Select carpet 1 AON Project Network for House Start 1 3 Design house and obtain financing Lay foundations 2 2 Build house Order and receive materials Select paint Select carpet Finish work

28 SITUATIONS IN NETWORK DIAGRAM B A A must finish before either B or C can start A C C both A and B must finish before C can start B A B C D both A and C must finish before either of B or D can start A B Dummy A must finish before B can start both A and C must finish before D can start C D 28

29 CONCURRENT ACTIVITIES Lay foundation 2 3 Order material Lay foundation Order material Dummy 4 (a) Incorrect precedence relationship (b) Correct precedence relationship 29

30 NETWORK EXAMPLE Illustration ti of network analysis of a minor redesign of a product and its associated packaging. The key question is: How long will it take to complete this project? 30

31 For clarity, this list is kept to a minimum by specifying only immediate relationships, that is relationships involving activities that "occur near to each other in time". 31

32 QUESTIONS TO PREPARE ACTIVITY NETWORK Is this a Start Activity? Is this a Finish Fiih Atiit? Activity? What Activity Precedes this? What Activity Follows this? What Activity is Concurrent with this? 32

33 CPM CALCULATION Path A connected sequence of activities leading from the starting event to the ending event Critical Path The longest path (time); determines the project duration Critical Activities All of the activities that make up the critical path 33

34 FORWARD PASS Earliest Start Time (ES) earliest time an activity can start ES = maximum EF of immediate predecessors Earliest finish time (EF) earliest time an activity can finish earliest start time plus activity time EF= ES + t Backward Pass Latest Start Time (LS) Latest time an activity can start without delaying critical path time LS= LF - t Latest finish time (LF) latest time an activity can be completed without delaying critical path time LS = minimum LS of immediate predecessors 34

35 CPM ANALYSIS Draw the CPM network Analyze the paths through the network Determine the float for each activity Compute the activity s float float = LS - ES = LF - EF Float is the maximum amount of time that this activity can be delay in its completion before it becomes a critical activity, i.e., delays completion of the project Find the critical path is that the sequence of activities and events where there is no slack i.e.. Zero slack Longest path through a network Find the project duration is minimum project completion time 35

36 CPM EXAMPLE: CPM Network f, 15 a, 6 g, 17 h, 9 i, 6 b, 8 d, 13 j, 12 c, 5 e, 9 36

37 CPM EXAMPLE ES and EF Times f, 15 a, g, 17 h, 9 i, 6 b, d, 13 j, 12 c, e, 9 37

38 CPM EXAMPLE ES and EF Times f, g, 17 h, 9 a, i, 6 b, c, d, 13 j, e,

39 CPM EXAMPLE f, 15 ES and EF Times a, g, 17 h, i, 6 b, c, d, 13 j, e, Project s EF = 33 39

40 CPM EXAMPLE LS and LF Times f, h, 9 a, 6 g, i, b, d, 13 j, c, e,

41 CPM EXAMPLE LS and LF Times f, h, a, 6 g, i, b, d, 13 j, c, e,

42 CPM EXAMPLE Float f, h, a, 6 g, i, b, d, 13 j, c, e,

43 CPM EXAMPLE Critical Path f, 15 a, 6 g, 17 h, 9 i, 6 b, 8 d, 13 j, 12 c, 5 e, 9 43

44 EXAMPLE Illustration of network analysis of a minor redesign of a product and its associated packaging. The key question is: How long will it take to complete this project? 44

45 For clarity, this list is kept to a minimum by specifying only immediate relationships, that is relationships involving activities that "occur near to each other in time". 45

46 Before starting any of the above activity, the questions asked would be "What activities must be finished before this activity can start" could we complete this project in 30 weeks? could we complete this project in 2 weeks? One answer could be, if we first do activity 1, then activity 2, then activity 3,..., then activity 10, then activity 11 and the project would then take the sum of the activity completion times, 30 weeks. What is the minimum possible time in which we can complete this project? 46

47 We shall see below how the network analysis diagram/picture we construct helps us to answer this question. 47

48 CRITICAL PATH TAKES 24 WEEKS FOR THE COMPLETION OF THE PROJECT 48

49 Packages are available to determine the shortest path and other relevant information. 49

50 Data entry window 50

51 Output of the package 51

52 PERT PERT is based on the assumption that an activity s duration follows a probability distribution instead of being a single value Three time estimates are required to compute the parameters of an activity s duration distribution: pessimistic time (t p ) - the time the activity would take if things did not go well most likely time (t m ) - the consensus best estimate of the activity s duration optimistic time (t o ) - the time the activity would take if things did go well Mean (expected time): t + + e = t p 4 t m t o 6 Variance: V t =σ 2 = t p - t o

53 PERT ANALYSIS Draw the network. Analyze the paths through the network and find the critical path. The length of the critical path is the mean of the project duration probability distribution which is assumed to be normal The standard deviation of the project duration probability distribution is computed by adding the variances of the critical activities (all of the activities that make up the critical path) and taking the square root of that sum Probability computations can now be made using the normal distribution table. 53

54 PROBABILITY COMPUTATION Determine probability that project is completed within specified time Z = x - µ σ where µ = t p = project mean time σ = project standard mean time x = (proposed ) specified time 54

55 NORMAL DISTRIBUTION OF PROJECT TIME Probability Zσ µ = t p x Time 55

56 PERT EXAMPLE Immed. Optimistic Most Likely Pessimistic Activity Predec. Time (Hr.) Time (Hr.) Time (Hr.) A B C A D A E A F B,C G B,C H E,F I E,F J D,H K G,I

57 PERT EXAMPLE PERT Network D A E H J C B I K F G 57

58 PERT EXAMPLE Activity Expected Time Variance A 6 4/9 B 4 4/9 C 3 0 D 5 1/9 E 1 1/36 F 4 1/9 G 2 4/9 H 6 1/9 I 5 1 J 3 1/9 K 5 4/9 58

59 PERT EXAMPLE Activity ES EF LS LF Slack A *critical B C * D E F * G H I * J K * 59

60 PERT EXAMPLE V path = V A + V C + V F + V I + V K = 4/ / /9 = 2 σ path = z = (24-23)/σ = (24-23)/ )/1 414 =.71 From the Standard Normal Distribution table: P(z <.71) = =

61 PROJECT COST 61

62 COST CONSIDERATION IN PROJECT Project managers may have the option or requirement to crash the project, or accelerate the completion of the project. This is accomplished by reducing the length of the critical path(s). The length of the critical path is reduced by reducing the duration of the activities on the critical path. If each activity requires the expenditure of an amount of money to reduce its duration by one unit of time, then the project manager selects the least cost critical activity, reduces it by one time unit, and traces that change through the remainder of the network. As a result of a reduction in an activity s time, a new critical path may be created. When there is more than one critical path, each of the critical paths must be reduced. If the length of the project needs to be reduced further, the process is repeated. 62

63 PROJECT CRASHING Crashing reducing project time by expending additional resources Crash time an amount of time an activity is reduced Crash cost cost of reducing activity time Goal reduce project duration at minimum cost 63

64 ACTIVITY CRASHING Crash cost Crashing activity Slope = crash cost per unit time Normal cost Normal Activity Normal time Crash time Activity time 64

65 TIME-COST RELATIONSHIP Crashing costs increase as project duration decreases Indirect costs increase as project duration increases Reduce project length as long as crashing costs are less than indirect costs Time-Cost Tradeoff Min total cost = optimal project time Total project cost Indirect cost Direct cost time 65

66 PROJECT CRASHING EXAMPLE

67 TIME COST DATA Activity Normal Normal Crash Crash Allowable slope time cost trs time cost trs crash htime

68 1 12 R R R Project duration = 36 From.. R R3000 R R200 Project To.. duration = 31 Additional cost = R R400 R R3000 R200 R R200 R

69 BENEFITS OF CPM/PERT Useful at many stages of project management Mathematically simple Give critical path and slack time Provide project documentation Useful in monitoring costs CPM/PERT can answer the following important questions: How long will the entire project take to be completed? What are the risks involved? Which are the critical activities or tasks in the project which could delay the entire project if they were not completed on time? Is the project on schedule, behind schedule or ahead of schedule? If the project has to be finished earlier than planned, what is the best way to do this at the least cost? 69

70 LIMITATIONS TO CPM/PERT Clearly defined, independent and stable activities Specified precedence relationships Over emphasis on critical paths Deterministic CPM model Activity time estimates are subjective and depend on judgment PERT assumes a beta distribution for these time estimates, but the actual distribution may be different PERT consistently underestimates the expected project completion time due to alternate paths becoming critical To overcome the limitation, Monte Carlo simulations can be performed on the network to eliminate the optimistic bias 70

71 COMPUTER SOFTWARE FOR PROJECT MANAGEMENT Microsoft Project (Microsoft Corp.) MacProject (Claris Corp.) PowerProject (ASTA Development Inc.) Primavera Project Planner (Primavera) Project Scheduler (Scitor Corp.) Project Workbench (ABT Corp.) 71

72 PRACTICE EXAMPLE A social project manager is faced with a project with the following activities: Activity Atiit Description iti Duration Social work team to live in village Social research team to do survey Analyse results of survey Establish mother & child health program Establish rural credit programme Carry out immunization of under fives 5w 12w 5w 14w 15w 4w Draw network diagram and show the critical path. Calculate project duration. 72

73 PRACTICE PROBLEM Activity Description Duration 1-2 Social work team to live in village 5w 1-3 Social research team to do survey 12w 3-4 Analyse results of survey 5w 2-4 Establish mother & child health program 14w 3-5 Establish rural credit programme 15w 4-5 Carry out immunization of under fives 4w

74 CONTOH 1: 100 KM B 2 60 KM D 40 KM 4 50 KM F 1 6 A 55 KM 25 KM 75 KM 5 3 E C 74

75 CONTOH 2 AKTIVITAS URAIAN AKTIVITAS PENDAHULUAN WAKTU PENYELESAIAN (HARI A Desain daftar pertanyaan - 4 B Desain sampling - 5 C Testing daftar pertanyaan dan A 4 perbaikan D Memilih calon intervierwer B 1 E Melatih interviewer D, A 2 F Membagi wilayah kepada interviewer B 4 G Pelaksanaan interview C, E, F 10 H Evaluasi hasil riset G 15 75