mis375 l06 ch06 projnetwork [compatibility mode]

8/9/2019 MIS375 L06 Ch06 ProjNetwork [Compatibility Mode]

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THE MANAGERIAL PROCESSTHE MANAGERIAL PROCESS Clifford F. GrayEric W. Larson

Third Edition

Clifford F. GrayEric W. Larson

Third EditionProjectManagementrojectManagement

Chapter 6Chapter 6

Developing a Project PlanDeveloping a Project Plan

Developing the Project PlanDeveloping the Project Plan

The Project Network

A tool used for planning, scheduling, monitoring project progress

Time, Cost, Performance

A graphic flow chart of the project plan

Depicts the project activities as well as their logical sequences,

interdependencies, and start and finish times.

Identifies the longest path through the network -the critical path

Use networks for non-trivial projects

Networks are displayed in universal formats

Easy to modify

Easy to update

Developing the Project PlanDeveloping the Project Plan

The Project Network

A roadmap

Provides the basis for scheduling labor and equipment

Enhances communication among project participants Provides a basis for budgeting cash flow

Provides an estimate of the entire projects duration

Highlights activities that are critical and can not be delayed

Identifies activities that can be delayed

Shows duration, start and finish times of individual activities

Minimizes surprises


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Network BasicsNetwork Basics

Activity: an element in the project that consumes time Work or wait

WBS Work acka es are used to build activities

An activity can be 1 or more work packages

Activities are placed in a sequence that provides for orderlycompletion of the project

Networks are built using nodes and arrows

Two Approaches

Activit -on-Node (AON)

Uses a node to depict an activity.

Activity-on-Arrow (AOA)

Uses an arrow to depict an activity.

Network BasicsNetwork Basics

Integration of WBS and Network is sometimesoverlooked, but many times crucial

De endenc timin se uencin of work acka es are not art,

,

of WBS

P.147

Manager derives activity time estimates from work package task

times

From Work Package to NetworkFrom Work Package to Network

WBS/Work Packages to Network

FIGURE 6.1

Constructing a Project NetworkConstructing a Project Network

Terminology

Activity: an element of the project thatrequ res me, u no necessar yresources

Usually one or more work package tasks

Merge Activity: an activity that has two ormore preceding activities on which it

B D

Parallel (Concurrent) Activities: Activities

that can occur independently and, ifdesired, not at the same time.


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Constructing a Project Network (contd)Constructing a Project Network (contd)

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; theshortest expected time in which the entire project can becompleted. Delays on the critical path will delay completion of theentire project.

C

A B D

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

Constructing a Project Network (contd)Constructing a Project Network (contd)

TerminologyEvent: 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 arrowflowing from it).

B

D

A C

Basic Rules to Follow in DevelopingBasic Rules to Follow in DevelopingProject NetworksProject Networks

Networks typically flow from left to right.

An activity cannot begin until all of its preceding activities arecomplete.

Arrows indicate precedence and flow and can cross over each other(Arrow length and angle are arbitrary for drawing convenience).

Identify each activity with a unique number; this number must be

greater than its predecessors.

Loopin is not allowed.

Conditional statements are not allowed (Ifthen)

Use single project start and stop nodes.

P.149

Basic RelationshipsBasic Relationships

Predecessor

An activity that must be completed immediately before an activity

Which activities must come immediatel before this activit ?

Successor An activity that must immediately follow an activity

Concurrent / Parallel

An activity that can occur while another activity is taking place


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ExampleExample

P. 151

raw ng e ne wor p aces e ac v es n e correcsequence

Once the network is completed we can calculate thetimes (dates) for completion for each activity as well asthe projects critical path

This is done by passing through the project

Network Computation ProcessNetwork Computation Process

Forward PassEarliest Times How soon can the activity start? (early startES)

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 non-critical activities be delayed? (slack or floatSL)

Forward Pass ComputationForward Pass Computation

Starting with the first activity

add activity times along each path in the network

ES + Duration = EF

Carry the early finish (EF) to the next activity where itbecomes its early start (ES) unless

The next succeeding activity is a merge activity, in whichcase the largest EF of all preceding activities is selected

Do a forward pass on Koll Business Center

Backward Pass ComputationBackward Pass Computation

Starting with the early finish time of the last activity

The early finish becomes the late finish of the last activity

Subtract duration for that activity to get its late start

LF - Duration = LS

Carry the late start (LS) to all predecessors where itbecomes its (their) late finish (LF) unless

The next preceding activity is a burst activity, in whichcase the smallest LF of all preceding activities isselected.


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Determining Slack (or Float)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, thereafter delaying the entire project

Can be positive, zero, negative

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

Zero slack (unless an imposed finish date exists)

Total Slack: Slack of the total pro ect

Free Slack: Amount of slack along an activity or chain of activitiesavailable without delay to the project

Critical ActivitiesCritical Activities

Mark critical path with heavy dashed arrows Critical activities represent approximately 10% of the

Close attention must be paid to critical activities soproject is not delayed

Slack / Critical Path NotesSlack / Critical Path Notes

Delaying activities with slack will impact the availabilityof slack for downstream activities

assign resources

Keep very close eyes on the critical path items, as theywill delay your project

Shortening a schedule requires adding resources to acritical activity. Choose the activity that costs the leasto s or en

Practical ConsiderationsPractical Considerations

Level of detail

As appropriate (project, cost, culture)

No conditional logic

No Looping

Activity Numbering

Predecessors should always be lower than their successors

Computer programs can do this

-


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Practical ConsiderationsPractical Considerations

Use of computers to develop networks Pert (Program Evaluation and Review Technique)

Gantt Bar Charts Henr Laurence Gantt 1861-1919 ,

P.163

Calendar dates need to be assigned

Weekends, holidays

Extended Network TechniquesExtended Network Techniquesto Come Close to Realityto Come Close to Reality

Start-Finish is not always the way activities really work.

Laddering (overlapping)

Activities can be broken into segments so the following activitycan begin sooner and not delay the work

e.g., Laying pipe (p.164)

Extended Network TechniquesExtended Network Techniquesto Come Close to Realityto Come Close to Reality

Lags (also overlapping) The minimum amount of time a dependent activity must be

delayed to begin or end.

Lengthy activities can be 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.

Can be used to sandbag be careful

Finish-to-Start

Start-to-Start

Finish-to-Finish (p.168)

Start-to-Finish

Hammock ActivitiesHammock Activities

Hammock Activity

An activity that spans over a segment of a project.

Duration of hammock activities is determined after the networkplan is drawn.

Hammock activities are used to aggregate sections of the projectto facilitate getting the right amount of detail for specific sections

of a project.

mis375 l06 ch06 projnetwork [compatibility mode]

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