Project Scheduling Techniques

Network Design, Project Scheduling

• Scheduling converts an action plan into an operating timetable.
• It's the basis for monitoring and controlling a project.
• Scheduling is more critical in projects than in production due to unique project natures.
• Customer-specified requirements, like JKR projects, are often based on a Work Breakdown Structure (WBS).

Introduction

• Schedules are crucial for project monitoring and control.
• A schedule translates the action plan into an operating timetable.
• Projects are more dynamic than production, demanding more scheduling attention.
• Customer-defined requirements frequently guide project scheduling, especially in projects like JKR projects, which often use WBS.

Network Techniques

• PERT (Program Evaluation and Review Technique): Developed by the US Navy with Booz Hamilton Lockheed on the Polaris Missile/Submarine program in 1958.
• CPM (Critical Path Method): Developed by El Dupont for Chemical Plant Shutdown projects around the same time as PERT.
• Both PERT and CPM use similar calculations.
• The primary difference is that PERT uses probabilistic time estimations, while CPM uses deterministic time estimations.
• Gantt charts are also used in scheduling.

Network

• A network is a graphical representation of activities and events.
• It displays the relationships of tasks/activities within a project.
• It effectively illustrates the dependencies between tasks in a logical sequence (precedence or succession).
• Networks are powerful planning and controlling tools.

Example of Simple Network - Survey

• The diagram visually showcases the tasks and their sequence in a survey project.
• It illustrates distinct activities, like planning a survey, hiring personnel, designing questionnaires, training personnel, selecting households, printing questionnaires, conducting surveys, and analyzing results.
• Each activity has a visual representation.

Example of Network - More Complex

• Diagram illustrates a more complex project (developing and marketing a new computer program).
• It depicts activities, such as program phases, renumbering routines, preparing operating instructions, and creating packages
• It includes preparing various support material, like brochures, and advertising plans.

Definition of Terms in a Network

• Activity: A portion of a project that consumes resources and time.
• Event: A point in time marking the beginning or end of one or more activities, often called 'nodes'.
• Network: The combination of all project activities and events.

Emphasis on Logic in Network Construction

• Network construction should be based on activity dependencies (logical or technical).
• "Approve Drawing" activity must follow "Prepare Drawing".
• Avoid building networks using only time logic.

Example 1 - A simple network

• Activities like buying plastic bodies, designing components, making components, and assembling the product are categorized, showing their immediate predecessors.
• Immediate predecessors are activities completed before starting a given activity.

Sequence of activities

• Activities A and B can begin anytime, unrelated to each other.
• Activity C cannot start until activity B concludes.
• Activity D commences only after both A and C have been completed.

Network of Four Activities

• The network diagram visually illustrates four activities (A, B, C, and D) and their sequence.
• Arcs between circles represent activities.
• The circles (nodes) represent points where activities start, end or transition between one task and another.

Example 2

• Develop a network diagram for a project based on provided activities and predecessors.
• Activities include A, B, C, D, E and F.

Network of First Five Activities

• A diagram illustrating the network of the first five activities (A, B, C, D, and E) of a project.
• It shows how Activities are interconnected or related, using circles (nodes) and lines (arcs).

Network of Seven Activities

• The network accurately identifies D, E, and F as immediate predecessors to G.
• Dummy activities are used to avoid conflicts or ambiguity, ensuring logical connections in activities with shared start/end points.

Examples of the Use of Dummy Activity

• Dummy activities are used to maintain logical connections in networks.

Scheduling with Activity Time

• Calculated total time for completing all activities.
• Activities can be simultaneously performed/conducted

Earliest Start & Earliest Finish Time

• The longest path through the network defines the critical path.
• Earliest start and finish times are calculated for each activity, starting at the project's origin (node 1) and using a starting time of 0.
• The formula EF = ES + t is used to find the earliest finish time of an activity.

Arc with ES & EF time

• The arcs of the network display expected activity time (t) along with their earliest start (ES) and finish (EF) times for each activity.

Network with ES & EF time

• Diagram displays earliest start (ES) and earliest finish (EF) times for activities in a network.
• The earliest start time of an activity is determined by the latest finish time for all activities entering the particular node.

Activity, duration, ES, EF, LS, LF

• Network diagram includes earliest start (ES), earliest finish (EF), latest start (LS), and latest finish (LF) times for each activity.

Latest Start & Latest Finish Time

• A backwards pass calculation is necessary to identify the critical path.
• Latest start (LS) and finish (LF) times for each activity are determined.
• Formula LS = LF - t is used to estimate the latest start time for an activity

Network with LS & LF time

• A diagram showing latest start (LS) and latest finish (LF) times for different activities.
• The latest finish time for an activity that enters a particular node equals the smallest of the latest start times for all activities leaving the node.

Slack or Free Time or Float

• Slack is the time an activity can be delayed without affecting project completion time.
• Slack for an activity is calculated as LF-EF or LS-ES.

Activity schedule for our example

• Table providing an activity schedule showing earliest and latest start/finish times, slack, and critical path status for each activity in a sample project.

Important Questions

• What's the project's total time?
• What are the scheduled start and end times for each activity?
• Which activities are critical for maintaining the project schedule?
• How flexible are activities not on the critical path?
• Slack time for all activities is documented.

Importance of Float (Slack) and Critical Path

• Slack (or float) indicates the extent an activity can delay without affecting project completion.
• The critical path is the sequence of activities from start to completion with zero slack.
• The critical path defines the project's minimum completion time.
• Shortening/extending a critical activity alters the overall project time.

Importance of Float (Slack) and Critical Path (cont)

• Project completion time should be managed by controlling activities on the critical path.
• Activities on the critical path should be prioritized if time constraints exist.
• Resources should not be wasted on non-critical activities.
• Some delay in non-critical activities could be allowed up to the slack limit.
• Total float defines the latitude of an activity.

PERT For Dealing With Uncertainty

• Estimating activity times under uncertainty can't be done as easily as when the times are known precisely, like in projects involving R&D, new products, or research and development etc.
• PERT uses three time estimations—optimistic (a), most likely (m), and pessimistic (b)—to calculate expected activity time (TE).
• Formula for Expected Value = (a + 4m + b) / 6
• Variance (V) is calculated: ( (b-a)/6 )^2
• Standard Deviation (δ) is the square root of variance.

Precedences And Project Activity Times

• This table lists optimistic, most likely, and pessimistic time estimates for various project activities (a, b, c, etc.), and their immediate predecessors.
• It also computes the expected time (TE) for each activity and the variance (V) and standard deviation.

The complete network

• A diagram depicting the overall project network, indicating activities and their durations.

Figure 8-13 The complete Network

• A clear illustration of the complete project network.

Critical Path Analysis (PERT)

• Table showing the latest start (LS), earliest start (ES), slack, and critical status for each activity in the project.

What deadline are you 95% sure of meeting?

• Calculations demonstrating the 95% confidence deadline.
• A deadline with a higher degree of confidence is determined, given the standard deviation and calculating Z to figure out a 95% chance of completion.

Comparison Between CPM and PERT

• CPM and PERT are different methodologies used in project management.
• The table shows how CPM handles one time estimate, but PERT is more versatile due to different time estimation considerations.

BENEFITS OF CPM / PERT NETWORK

• A framework to plan, schedule, control, and monitor projects.
• Illustrates task/activity interactions and dependencies, and proper communication.
• Enables accurate project completion date determination.
• Identifies critical activities to pinpoint possible project delays.

BENEFITS OF CPM / PERT NETWORK (cont.)

• Activities with slack can be delayed without impacting the project completion date.
• The network precisely calculates dates for project tasks to ensure schedule adherence.
• Coordinating tasks to avoid resource or timing conflicts is vital for consistent progress.
• Shows work tasks that can run concurrently to meet deadlines.

Gantt Charts

• Gantt charts are useful for displaying work progress over time.
• They effectively visualize work and time relationships.
• Gantt charts can be directly or indirectly derived from the CPM/PERT network diagram. (They are complementary)

Modified PERT/CPM diagram from network

• This diagram is a visual representation of a project showing scheduled start and finish times, actual progress, current date, milestones, and completed milestones.

Gantt Chart

• The specific chart shows tasks (activities) and timeframes.
• The Gantt chart visualizes project progress over time.

Gantt chart showing progress of project on day 22

• This chart displays the project's progress up to day 22.

Relating the budget to the Gantt chart schedule

• This chart correlates the project budget to the schedule's timeframe, providing a visual connection between financial resources and the project's plan.

Gantt Charts and CPM/PERT Networks

• Gantt charts are extremely straightforward to follow and comprehend, but they do not adequately address project logic or constraints effectively.
• Use Gantt charts to enhance your CPM/PERT networks; do not substitute the network for Gantt charts.

RESOURCE ANALYSIS AND SCHEDULING

• Project execution feasibility is determined by resource availability.
• Assessing resource needs ensures project goals can be achieved.
• Proper and efficient resource utilization is crucial.
• Resource planning is vital for project timeline and budget management, especially in projects like the development of a new product or R&D.

Activities D, E, F, G and H require fitters

• Diagram depicting planned time constraints based on the number of needed personnels for different project activities.

Convert the bar chart to a histogram

• A visual depiction of resource needs across time, showing fluctuations and maximum demand.

Additional Restriction - no fitters available until the end of week 5

• revised project schedule incorporating the restricted start time for fitters.

Resource constraints

• Relation between resource constraints associated with variations in resource requirements and availability.
• The impact of variations is analyzed to illustrate easier control aspects, and resources utilization.
• Critical resource variations are important to monitor, especially issues with manpower, to maintain project control.

Histogram showing large resource variations

• Shows significant variations in resource needs relating to time.

Explore the critical aspects of project scheduling and network design in this quiz. Learn about the importance of schedules in monitoring projects and the methodologies like PERT and CPM. Understand how customer requirements and a Work Breakdown Structure (WBS) play a role in effective scheduling.