Network Analysis : Pert & C P Management
- 1. Network Analysis : Pert & CPM Network Analysis : Pert & CPM BY BY Dr.Prudvi Dr.Prudvi Ph.D ( structures) Ph.D ( structures)
- 2. Introduction Introduction Network analysis is one of the important tools for project Network analysis is one of the important tools for project management. management. Whether major or minor a project has to be completed in a definite Whether major or minor a project has to be completed in a definite time & at a definite cost. time & at a definite cost. The necessary information of any particular data can be The necessary information of any particular data can be represented as a project network. represented as a project network. These techniques are very useful for planning, scheduling and These techniques are very useful for planning, scheduling and executing large-time bound projects involving careful co-ordination executing large-time bound projects involving careful co-ordination of variety of complex and interrelated activities of variety of complex and interrelated activities
- 3. Objectives of network analysis Objectives of network analysis Helpful in planning Helpful in planning Inter-relationship of various activities Inter-relationship of various activities Cost control Cost control Minimisation of maintenance time Minimisation of maintenance time Reduction of time Reduction of time Control on idle resources Control on idle resources Avoiding delays, interruptions Avoiding delays, interruptions
- 4. Applications of network analysis Applications of network analysis Planning, scheduling, monitoring and control of Planning, scheduling, monitoring and control of large and complex projects. large and complex projects. Construction of factories, highways, building, Construction of factories, highways, building, bridges, cinemas etc. bridges, cinemas etc. Helpful to army for its missile development. Helpful to army for its missile development. Assembly line scheduling Assembly line scheduling Installation of computers and high tech Installation of computers and high tech machineries machineries To make marketing strategies To make marketing strategies
- 5. Methodology Involved in Network Methodology Involved in Network Analysis Analysis Describing the Project Diagramming the network Estimating the time of completion Deterministic estimates Probabilistic estimates Monitoring the project progress
- 6. Key terminology Key terminology Activity : All projects may be viewed as composed of activities. Activity : All projects may be viewed as composed of activities. It is the smallest unit of work consuming both time& resources It is the smallest unit of work consuming both time& resources that project manager should schedule & control. that project manager should schedule & control. An activity is represented by an arrow in network diagram An activity is represented by an arrow in network diagram The head of the arrow shows sequence of activities.
- 7. Classification of activities Classification of activities Predecessor activity Predecessor activity: Activities that must be completed immediately : Activities that must be completed immediately prior to the start of another activity are called predecessor activities. prior to the start of another activity are called predecessor activities. Successor activity Successor activity : activities that cannot be started until one or : activities that cannot be started until one or more of other activities are completed but immediately succeed them more of other activities are completed but immediately succeed them are called successor activities. are called successor activities. Concurrent activities Concurrent activities: activities that can be accomplished together : activities that can be accomplished together are known as concurrent activities. are known as concurrent activities. Dummy activity Dummy activity: An activity which does not consume any resource : An activity which does not consume any resource but merely depicts the dependence of one activity on other is called but merely depicts the dependence of one activity on other is called dummy activity. It is introduced in a network when two or more dummy activity. It is introduced in a network when two or more parallel activities have the same start and finish nodes. parallel activities have the same start and finish nodes.
- 8. Event Event The beginning & end of an activities are called as events . The beginning & end of an activities are called as events . Events are represented by numbered circles called nodes. Events are represented by numbered circles called nodes. i j Event start Event finish
- 9. Types of Events Types of Events Merge event Merge event Burst event Burst event Merge & Burst Event Merge & Burst Event
- 10. Path & Network Path & Network An unbroken chain of activity arrows connecting the initial event to An unbroken chain of activity arrows connecting the initial event to some other event is called a path. some other event is called a path. A network is the graphical representation of logically & sequentially A network is the graphical representation of logically & sequentially connected arrows & nodes representing activities & events of a connected arrows & nodes representing activities & events of a project . It is a diagram depicting precedence relationships between project . It is a diagram depicting precedence relationships between different activities. different activities.
- 11. Guidelines for Network Guidelines for Network Construction Construction A complete network diagram should have one stand point & one A complete network diagram should have one stand point & one finish point. finish point. The flow of the diagram should be from left to right. The flow of the diagram should be from left to right. Arrows should not be crossed unless it is completely unavoidable. Arrows should not be crossed unless it is completely unavoidable. Arrows should be kept straight & not curved or bent. Arrows should be kept straight & not curved or bent. Angle between arrows should as large as possible. Angle between arrows should as large as possible. Each activity must have a tail or head event.. No two or more Each activity must have a tail or head event.. No two or more activities may have same tail & head events. activities may have same tail & head events. Once the diagram is complete the nodes should be numbered from Once the diagram is complete the nodes should be numbered from left to right. It should then be possible to address each activity left to right. It should then be possible to address each activity uniquely by its tail & head event. uniquely by its tail & head event.
- 12. Stages for project management Stages for project management Project planning stages : in order to Project planning stages : in order to visualize the sequencing or precedence visualize the sequencing or precedence requirements of the activities in a project, it requirements of the activities in a project, it is helpful to draw a network diagram. is helpful to draw a network diagram. Scheduling stage : once all work packages Scheduling stage : once all work packages have been identified and given unique have been identified and given unique names or identifiers, scheduling of the names or identifiers, scheduling of the project project
- 13. Project control stage : Project control stage : project control refers to evaluating project control refers to evaluating actual progress against the plan. If actual progress against the plan. If significant differences are observed, then significant differences are observed, then the scheduling and resources allocation the scheduling and resources allocation decisions are changed to update and decisions are changed to update and revise the uncompleted part of the project revise the uncompleted part of the project
- 14. Advantages Advantages Planning & controlling projects Planning & controlling projects Flexibility Flexibility Designation of responsibilities Designation of responsibilities Achievement of objective with least cost Achievement of objective with least cost Better managerial control Better managerial control
- 15. Limitations of PERT /CPM Limitations of PERT /CPM Network diagrams should have clear starting & ending points , Network diagrams should have clear starting & ending points , which are independent of each other which may not be possible in which are independent of each other which may not be possible in real life. real life. Another limitation is that it assumes that manager should focus on Another limitation is that it assumes that manager should focus on critical activities. critical activities. Resources will be available when needed for completion for an an Resources will be available when needed for completion for an an activity is again unreal. activity is again unreal.
- 16. Example Activity Activity Predecessor Predecessor activity activity A A none none B B none none C C A A D D A A E E B B F F C C G G D & E D & E 1 3 2 5 4 6 A B C D E F G
- 17. Draw the network diagram for the following Activity Activity Predecessor Predecessor activity activity A A none none B B A A C C A A D D B B E E C C F F D ,E D ,E
- 19. Critical path Critical path Those activities which contribute directly to the overall duration of Those activities which contribute directly to the overall duration of the project constitute critical activities, the critical activities form a the project constitute critical activities, the critical activities form a chain running through the network which is called critical path. chain running through the network which is called critical path. Critical event Critical event : the slack of an event is the difference between the : the slack of an event is the difference between the latest & earliest events time. The events with zero slack time are latest & earliest events time. The events with zero slack time are called as critical events. called as critical events. Critical activities Critical activities : The difference between latest start time & : The difference between latest start time & earliest start time of an activity will indicate amount of time by which earliest start time of an activity will indicate amount of time by which the activity can be delayed without affecting the total project the activity can be delayed without affecting the total project duration. The difference is usually called total float. Activities with 0 duration. The difference is usually called total float. Activities with 0 total float are called as critical activities total float are called as critical activities
- 20. Critical path Critical path The critical path is the longest path in the network from the starting The critical path is the longest path in the network from the starting event to ending event & defines the minimum time required to event to ending event & defines the minimum time required to complete the project. complete the project. The critical path is denoted by darker or double lines. The critical path is denoted by darker or double lines.
- 21. Difference between PERT & CPM Difference between PERT & CPM PERT A probability model with uncertainty in activity duration . The duration of each activity is computed from multiple time estimates with a view to take into account time uncertainty. It is applied widely for planning & scheduling research projects. PERT analysis does not usually consider costs. CPM A deterministic model with well known activity times based upon the past experience. It is used for construction projects & business problems. CPM deals with cost of project schedules & minimization.
- 22. Float Float : : There are many activities where the There are many activities where the maximum time available to finish the activity is maximum time available to finish the activity is more than the time required to complete the more than the time required to complete the activity. The difference between the two times is activity. The difference between the two times is known as float available for the activity known as float available for the activity. . There are three types of float: There are three types of float: Total float Total float : : It is the spare time available It is the spare time available when all preceding activities occur at earliest when all preceding activities occur at earliest possible times & all success ding activities occur possible times & all success ding activities occur at latest possible times at latest possible times. . Total float = Ls – Es or Lf – Ef Total float = Ls – Es or Lf – Ef
- 23. Free float Free float : time available when all preceding : time available when all preceding activities occur at the earliest possible time &all activities occur at the earliest possible time &all succeeding activities also occur at the earliest succeeding activities also occur at the earliest possible times. possible times. Free float Free float = total float - head event slack = total float - head event slack Independent Float Independent Float : it may be defined as : it may be defined as the amount of time by which the start of an the amount of time by which the start of an activity can be delayed without affecting the activity can be delayed without affecting the earliest start time of any successor activity , earliest start time of any successor activity , assuming that preceding activity has finished at assuming that preceding activity has finished at its latest finish time. its latest finish time. Independent Float = free float – tail event slack Independent Float = free float – tail event slack
- 24. PERT PERT PERT is designed for scheduling complex projects that PERT is designed for scheduling complex projects that involve many inter-related tasks. it improves planning involve many inter-related tasks. it improves planning process because: process because: 1. 1. It forms planner to define the projects various It forms planner to define the projects various components activities. components activities. 2. 2. It provides a basis for normal time estimates & yet It provides a basis for normal time estimates & yet allows for some measure of optimism or pessimism in allows for some measure of optimism or pessimism in estimating the completion dates. estimating the completion dates. 3. 3. It shows the effects of changes to overall plans they It shows the effects of changes to overall plans they contemplated. contemplated. 4. 4. It provides built in means for ongoing evaluation of the It provides built in means for ongoing evaluation of the plan. plan.
- 25. ESTIMATING ACTIVITY TIMES ESTIMATING ACTIVITY TIMES Optimistic time ( t Optimistic time ( t0 0 ) ) : is that time estimate of an : is that time estimate of an activity when everything is assumed to go as per plan. activity when everything is assumed to go as per plan. In other words it is the estimate of minimum possible In other words it is the estimate of minimum possible time which an activity takes in completion under ideal time which an activity takes in completion under ideal conditions. conditions. Most likely time ( t Most likely time ( tm m ) ) : the time which the activity will : the time which the activity will take most frequently if repeated number of times. take most frequently if repeated number of times. Pessimistic time ( tp) Pessimistic time ( tp) : : the unlikely but possible the unlikely but possible performance time if whatever could go wrong , goes performance time if whatever could go wrong , goes wrong in series. In other words it is the longest time wrong in series. In other words it is the longest time the can take. the can take.
- 26. EXPECTED TIME EXPECTED TIME The times are combined statically to develop the The times are combined statically to develop the expected time t expected time te e . . t te e = = to + 4tm + tp to + 4tm + tp 6 6 Standard deviation of the time of the time required to Standard deviation of the time of the time required to complete the project complete the project = = tp - to tp - to 6 6