activity on arc and activity on node

7/23/2019 Activity on Arc and Activity on Node

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DEVELOPING A PROJECT PLAN


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Developing the Project Plan

A flow chart that graphicallydepicts the sequence,interdependencies, and start andfinish times of the project job planof activities that is the critical path

through the network

TheProject

Network


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Project Network

Provides the basis for scheduling labor and equipment.

Enhances communication among project participants.

Provides an estimate of the projects duration

Provides a basis for budgeting 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

WBS/Work Packages to Network


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From Work Package to Network


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Constructing a Project Network

Activity: an element of theproject that requires time.

Merge activity: an activitythat has two or morepreceding activities onwhich it depends.

Parallel (concurrent)activities: Activities that canoccur independently and, ifdesired, not at the sametime.

Terminology A

C

B D


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D

C

A B

Path: a sequence ofconnected, dependentactivities.

Critical path: the longest paththrough the activity networkthat allows for the completionof all project-related activities;the shortest expected time inwhich the entire project can

be completed. Delays on thecritical path will delaycompletion of the entireproject.

Terminology

(Assumes that minimum of A + B > minimum of C in length of t imes to complete activities.)


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B

D

A C

Event: a point in timewhen an activity is

started or completed. Itdoes not consume time.

Burst activity: an activitythat has more than one

activity immediatelyfollowing it (more thanone dependency arrowflowing from it).

Terminology


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Two Approaches

Uses anode to

depict anactivity

Activity-on-Node

(AON)

Uses anarrow todepict anactivity

Activity-on-Arrow

(AOA)


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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 preceding connected activitiesare complete.

Arrows indicate precedence and flow and can cross over eachother.

Identify each activity with a unique number; this number must begreater than its predecessors.

Looping is not allowed.

Conditional statements are not allowed.

Use common start and stop nodes.


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Comparison of AON and AOA

Methods


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ACTIVITY ON NODE


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Activity-on-Node Fundamentals


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Activity-on-Node Fundamentals


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Network Information


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Koll Business CenterPartial

Network


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Koll Business CenterComplete

Network


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Network Computation Process

Forward PassEarliest Times

How soon can the activity start? (early startES)

How soon can the activity finish? (early finishEF)

How soon can the project finish? (expected timeET)

Backward PassLatest Times

How late can the activity start? (late startLS)

How late can the activity finish? (late finishLF)

Which activities represent the critical path?

How long can it be delayed? (slack or floatSL)


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Network Information


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Activity-on-Node Network


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Forward Pass


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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 whereit becomes its early start (ES)

The next succeeding activity is a merge activity, inwhich case the largest EF of all preceding activitiesis selected.


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Backward Pass


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Backward Pass Computation

Subtract activity times along each path in thenetwork (LF - Duration = LS).

Carry the late start (LS) to the next activity where itbecomes its late finish (LF)

The next succeeding activity is a burst activity, inwhich case the smallest LF of all preceding activitiesis selected.


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Determining Slack (or Float)

Free Slack (or Float)

The amount of time an activity can be delayed without

delaying connected successor activitiesTotal Slack

The amount of time an activity can be delayed withoutdelaying the entire project

The critical path is the network path(s) that has (have) the leastslack in common.


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Sensitivity of a Network

Function of:

The number of critical paths

The amount of slack across near critical

activities

The likelihood the original critical path(s) will changeonce the project is initiated.


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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


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Air Control Project


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Air Control Project


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Extended Network Techniques

to Come Close to Reality

Laddering

Activities are broken into segments so the following activity canbegin sooner and not delay the work.

Lags

The minimum amount of time a dependent activity must bedelayed to begin or end

Lengthy activities are broken down to reduce the delay in thestart of successor activities.

Lags can be used to constrain finish-to-start, start-to-start,finish-to-finish, start-to-finish, or combination relationships.


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Example of Laddering Using

Finish-to-Start Relationship


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Use of Lags

Use of Lags to

Reduce Detail


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New ProductDevelopment

Process


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Use of Lags

Finish-to-Finish

Relationship

Start-to-Finish

Relationship


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Network Using Lags


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AOA


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Activity-on-Arrow Network

Building Blocks


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Fundamentals


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Fundamentals


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Koll Center Project: Network

Information


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Partial Koll Business Center AOA

Network


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Partial AOA Koll Network


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Partial AOA Koll Network


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Activity-on-Arrow Network:

Forward Pass


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Activity-on-Arrow Network:

Backward Pass



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Activity on Arrow Network

Backward Pass, Forward Pass, and

Slack

l d


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Air Control Inc. Custom Order

ProjectAOA Network Diagram


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END OF CHAPTER

activity on arc and activity on node

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