PM Session 5

Project Management Session 5

Project Planning

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Session Outcome

• Following this session the delegate should be able to develop the following, given an appropriate case study:

– Tabulated sequence of activities;– Network diagram (AON);– Calculate a Forward Pass;– Calculate a Backward Pass;– Identify the Critical Path for the relevant

network diagram.

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Preamble

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Session Outcomes

Project planning is about sequencing and scheduling…

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Developing the Project Plan

Project planning is about sequencing and scheduling…

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Developing the Project Plan

Fundamental to this is the project network

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Developing the Project Plan

• The Project Network:

– A tool for planning, scheduling and monitoring project progress;

– Developed from the WBS;

– A flow chart that graphically depicts the sequence, interdependencies, and start and finish times of the project;

– Show activities that are the critical path through the network:

• Provides the basis for scheduling labor and equipment;

• Enhances communication among project participants;

• Provides an estimate of the project’s duration;

• Provides a basis for budgeting and cash flow;

• Identifies activities that are critical;

• Highlights activities that are “critical” and can not be delayed;

• Help managers get and stay on plan.

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From Work Package to Network

• Graphical sequence showing relationships, interdependencies and activities required to complete the project;

• Remember an activity consumes time;

• The link between the network diagram and the WBS is the work package – it is here that the activities are identified, to be used in the network diagram;

• However, the activity in the network diagram differs in terms of the following:

– It only shows time (start, end, duration ) and identifies an activity – the work package shows more information

– An activity can (but does not have to) include more than one work package;

– The work package are developed independently from each other, while the activities are depicted to show interrelationships and dependencies

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From Work Package to Network

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From Work Package to Network

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From Work Package to Network

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Constructing a Project Network

• Terminology:

– Activity: an element of the project that consumes time;

– Merge Activity: an activity that has two or more preceding activities on which it depends;

– Parallel (Concurrent) Activities (Relationships): Activities that can occur independently and, if desired, not at the same time.

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Constructing a Project Network

• Terminology:– Event: a point in time when an activity is

started or completed. It does not consume time;

– Burst Activity: an activity that has more than one activity immediately following it (more than one dependency arrow flowing from it).

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Constructing a Project Network

• Two Approaches:– Activity-on-Node

(AON):• Uses a node to

depict an activity.– Activity-on-Arrow

(AOA):• Uses an arrow to

depict an activity.

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Constructing a Project Network

• Terminology:

– Path: a sequence of connected, dependent activities;

– Critical path: the longest path through the activity network that allows for the completion of all project-related activities;

– The shortest expected time in which the entire project can be completed;

– Delays on the critical path will delay completion of the entire project.

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Constructing a Project Network

3/22/2006

Discretionary Relationship in Series

Early Start

DurationEarly Finish

Late Start SlackLate

Finish

Task Name

Early Start

DurationEarly Finish

Late Start SlackLate

Finish

Task Name

Early Start

DurationEarly Finish

Late Start SlackLate

Finish

Task Name

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Constructing a Project Network

3/22/2006

Mandatory Relationship in Series

Early Start

DurationEarly Finish

Late Start SlackLate

Finish

Task Name

Early Start

DurationEarly Finish

Late Start SlackLate

Finish

Task Name

Early Start

DurationEarly Finish

Late Start SlackLate

Finish

Task Name

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Basic Rules to Follow in Developing Project Networks

• Networks typically flow from left to right;• An activity cannot begin until all of its preceding activities are

complete;• Arrows indicate precedence and flow and can cross over each

other;• Identify each activity with a unique number; this number must

be greater than its predecessors;• Looping is not allowed;• Conditional statements are not allowed;• Use common start and stop nodes.

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Basic Rules to Follow in Developing Project Networks

• First step = create the sequence in a tabular format

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Network Information

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Basic Rules to Follow in Developing Project Networks

• Second step = create the sequence in network format

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Activity-on-Node Fundamentals

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Activity-on-Node Fundamentals

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Koll Business Center—Partial Network

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Koll Business Center—Complete Network

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Basic Rules to Follow in Developing Project Networks

• Third step = determine and record activity duration’s (here referred to as time)

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Network Information

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Activity-on-Node Network

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Basic Rules to Follow in Developing Project Networks

• Fourth step = Determine early start and finish dates (calculating the so called forward pass)

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Forward Pass Computation

• A Forward Pass through the network determines the earliest times each activity can start and finish;

• Forward Pass:

– How soon can the activity start? (early start—ES)

– How soon can the activity finish? (early finish—EF).

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Forward Pass Computation

• The earliest start time (EST) for the initial activity in a project is “time zero”;

• The EST of an activity is equal to the latest early finish time of the activities directly preceding it;

• The EFT of an activity is equal to its EST plus the time (duration) required to perform the activity.

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Forward Pass Computation

• Add activity times along each path in the network (ES + Duration = EF);

• Carry the early finish (EF) to the next activity where it becomes its early start (ES) unless…;

• The next succeeding activity is a merge activity, in which case the largest EF of all preceding activities is selected.

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Activity-on-Node Network Forward Pass

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Activity-on-Node Network Forward Pass

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Activity-on-Node Network Forward Pass

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Basic Rules to Follow in Developing Project Networks

• Fifth step = Determine late start and finish dates (calculating the so called backward pass)

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Backward Pass Computation

• A Backward Pass through the network determines the latest times each activity can start and finish without delaying completion of the project;

• Backward Pass:

– How late can the activity start? (late start—LS);

– How late can the activity finish? (late finish—LF).

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Backward Pass Computation

• Subtract activity times along each path in the network (LF - Duration = LS);

• Carry the late start (LS) to the next activity where it becomes its late finish (LF); unless

• The next succeeding activity is a burst activity, in which case the smallest LF of all preceding activities is selected.

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Activity-on-Node Network Backward Pass

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Network Computation Process

• The latest finish time (LFT) for the final activity in a project is equal to its EFT as determined by the forward pass;

• The LFT for any other activity is equal to the earliest LST of the activities directly following (or succeeding) it;

• The LST of an activity is equal to its LFT minus the time (duration) required to perform the activity.

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Basic Rules to Follow in Developing Project Networks

• Using Slack and Float

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Determining Slack (or Float)

• Slack (or Float):– The amount of time an activity can be delayed

after the start of a longer parallel activity or activities

• Total slack:– The amount of time an activity can be delayed

without delaying the entire project• The critical path is the network path(s) that has

(have) the least slack in common- normally Zero.

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Determining Slack (or Float)

• Slack:– If slack in an activity on a path is used, the ES of all

activities that follow in that chain will be delayed and their slack reduced. Use of total slack should therefore be coordinated with all participants in the activities that follow in that chain;

• Free slack:– Free slack, however is unique because the activity can be

delayed without delaying the ES of activities following it. Free slack is defined as the difference between the EF of an activity and the ES of the activity that follows. Only activities where that occur at the end of a chain of activities (usually where you have a merge activity) can have free slack – Free slack does not affect the activities following it.

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Activity-on-Node Network with Slack

23535200

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Activity-on-Node Network with Slack

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Activity-on-Node Network with Slack

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Activity-on-Node Network with Slack

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Practical Considerations

• Network Logic Errors;• Activity Numbering;• Use of Computers to

Develop Networks;• Calendar Dates;• Multiple Starts and

Multiple Projects.

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Illogical Loop

FIGURE 6.9

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Network to Gantt

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Network to Gantt