CHAPTER VIII CPM-PERT Instructor : Lect.Volkan ÇETİNKAYA

“A project is a series of activities directed to accomplishment of a desired objective.” Plan your work first…...then work your plan!

 PERT: (Project Evaluation and Review Technique  CPM: (Critical Path Method)

 Building, Airport, Roadway and similar construction projects.  Loading of new computer systems.  Design of new products.  Ship Constructing

 When will the project finish?  Which critical activities are there?And not?  What’s the probability of finishing the project in a definite term?  Where is the project?Going on accurately?  Is the project under or below the budget?  Are there adequate resources for the completion of project?  If it is planned to complete the project before planned time, How can it be done by least cost?

 CPM: For certain activities, it may be possible to decrease their completion times by spending more money.How does this affect the overall completion time of the project.  PERT: It has probability, It is for a particular activity the most likely completion time is 4 weeks but it could be anywhere between 3 weeks and 8 weeks.

 CPM: In CPM activities are shown as a network of precedence relationships using activity-on-node network construction.  Single estimate of activity time  Deterministic activity times  Used in Production management-for the jobs of repetitive in nature where the activity time estimates can be predicted with considerable certainty due to existance of past experience

 CPM’de faaliyetlerin süreleri kesin olarak bilinmektedir.  PERT’te faaliyetlerin süre ve maliyetleri kesin olarak bilinmemekte, bu veriler rassal değişkenler olarak atanmaktadır. Dolayısıyla elde edilen kritik yol bir “olasılık kritik yolu”dur.

 PERT: In PERT activities are shown as a network of precedence relationships using activity-on-arrow network construction.  Multiple estimate of activity time  Probabalistic activity times  Used in Project Management-for non-repetitive jobs(research and development works) where the time and cost estimates tend to be quite uncertain.

Advantages - Gantt charts are quite commonly used. They provide an easy graphical representation of when activities (might) take place. Limitations - Do not clearly indicate details regarding the progress of activities - Do not give a clear indication of interrelation ship between the separate activities

 Arrows: An arrow leads from tail to head directionally.It indicates ACTIVITY, a time consuming effort that is required to perform a part of the work.  Nodes: A node is represented by a circle. It indicates EVENT, a point in time where one or more activities start and/or finish.

 Describe the project and important activities.  Describe the relationships among facilities.  Draw the project network.  Determine time and cost of all activities.  Compute the longest way(critical path) of the network.  Use the network to plan, to schedule follow and control the project.

 A new founded company wants to design a product. Below the activities, priority relationships and activity durations were given. Draw the project network. ActivityPredecessorDuration A: Construction of production lines-8 B:Purchasing-11 C: Production of semi finished product-1A10 D: Production of semi finished product-2B7 E: testing of semi finished product-2D13 F: AssemblyC,E15

 □ j = Earliest occurence time of event ‘j’  ∆ j = Latest occurence time of event ‘j’  D ij = Duration of activity

 Forward Pass: (Earliest Occurence Times) The computations start at node 1 and advance recursively to end node n.  Backward Pass : (Latest Occurence Times) Following the completion of the forward pass, the backward pass computations starts at node n and end at node 1.

 An activity(i,j) will be critical if it satisfies these 3 conditions.  □ i = ∆ i  □j = ∆ j  ∆j - ∆i = □j - □ i = Dij

 Time Schedule for Example 3

 Draw the project network  Compute the critical path according to the data below ActivityPredecessorDuration A: Construction of production lines-8 B:Purchasing-11 C: Production of semi finished product-1A10 D: Production of semi finished product-2B7 E: testing of semi finished product-2D13 F: AssemblyC,E15

 PERT: Project Evaluation and Review Technique. Like CPM, but ist is a probabilistic model.  In PERT, activities fall in to 3 categories:  O : Optimistic  P : Pessimistic  M : Medium

 Let’s look at a project with 8 events and 11 activities.  QUESTIONS:  Draw the network of the project.  Compute expected time and variance of each activity.  Find critical path.  Compute the standart deviation of dispersion proving expected time of project.  What is the probability of completion of the project in 19 days or less than 19 days?

 Draw the network of the ship construction project.  Compute expected time and variance of each activity.  Find critical path.  Compute the standart deviation of dispersion proving expected time of project.  What is the probability of project completion in 36 weeks? ActivityNameTRProcessedorOMP APermissionsİzinler-234 BBudget PreperationBütçe Hazırlık-222 CDraft A,B237 DConstructingKaba İnşaatC579 EOuter InstallationDış TesisatD3411 FElectrical WorksElektrik İşleriD3510 GInner Installationİç TesisatE5610 HOuter PaintingDış BoyaG234 IInner Paintingİç BoyaF,H456 JOtherDiğer İşlerH234 KSubmittalTeslimI,J234