LECTURE 5

Scheduling Techniques

Introduction

An important part of project planning is determining the logical workflow of the various activities you identified in the WBS.

Network diagrams are used that represent a graphical flow plan of activities that must be accomplished to complete the project.

The diagram illustrates which activities must be performed in sequence.

It also shows the planned sequence of steps, with all dependencies.

Project management software will automatically prepare network diagrams and bar charts. 2

Scheduling techniques

Gantt or bar charts

Milestone charts

Line of balance

Networks Program Evaluation and Review Technique (PERT)

Arrow Diagram Method (ADM) [Sometimes called the Critical Path Method (CPM)]

Precedence Diagram Method (PDM)

Graphical Evaluation and Review Technique (GERT)

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Advantages of Scheduling techniques

Basis for planning and predicting and how to use the resources

Provide visibility to control

Help management evaluate alternatives

Basis for obtaining facts for decision making

Utilize time network analysis

Basic structure for reporting information

Reveal interdependencies of activities

Identify the longest path or critical path

Aid in scheduling risk analysis4

interdependencies of activities

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Advantages of Scheduling techniques

Basis for planning and predicting and how to use the resources

Provide visibility to control

Help management evaluate alternatives

Basis for obtaining facts for decision making

Utilize time network analysis

Basic structure for reporting information

Reveal interdependencies of activities

Identify the longest path or critical path

Aid in scheduling risk analysis6

GANTT Chart

A Gantt chart is a type of bar chart, illustrate the start and finish dates of the terminal tasks and summary tasks of a project

A Gantt chart is eveloped by Karol Adamiecki in 1896, and independently by Henry Gantt in the 1910s

A Gantt chart is one of the most popular and useful tool of showing activities (tasks or events) displayed against time

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8Gantt Chart Example

JobDay

1Day

2Day

3Day

4Day

5Day

6Day

7Day

8

A

B

C

Now

Maintenance

Start of an activity

End of an activity

Scheduled activity time allowed

Actual work progress

Nonproduction time

Point in time when chart is reviewed

Milestone schedules

A tool used to mark specific points along a project timeline. They focus on major progress points that must be reached to achieve success.

Project milestone schedules contains information:

Project start date

Project end date

Other milestones (review meetings or testing)

Data items (deliverables or reports)

Milestones are a good means to determine if your project is on schedule and a useful tool for reporting to management

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Milestone schedules

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Network analyis

The major disadvantage of GANTT and milestone is the inability to show the interdependencies between events and activities

Network analysis can provide valuable information for planning, integration of plans, time studies, scheduling and resource management.

Network are composed of events and acivities

There are two different format diagram

AON: Activities on the node (AIB- Activities in the box)

AOA: Activities on the arrow

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AON: Activities On the Node

Start

B

DigTrench

A

Order Pipe

C

DeliverPipe

D

LayPipe

Finish

Precedence Diagram Method

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AOA: Activities On the Arrow

6 3

COMPLETE TESTING COMPLETE FINAL REPORT

3 WEEKS

LEGEND

EVENT

ACTIVITY

ACTIVITY

Standard PERT Nomenclature13

AOA: Terminology

Event: equivalent to a milestone indicating when activity starts or finish

Activity: Element of work must be accomplished

Duration: Total time required to complete the activity

Critical path: The longest path thru the network and determines the duration of the project

Dummy activity: showing the precedential relationships between activities and consuming zero time

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Dependencies

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26 18

31

7

18

31

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BURST POINT SINK

15

16

a

b

c

d

e1

a

b

c

e

d

Activity c must not precede activity e Which one is correct?

WRONG RIGHT

Dependencies

Simplified PERT Network

1 9

3

4

2 8765

LEGEND: (TIME = WEEKS)

EVENT

ACTIVITY

CRITICAL PATH ACTIVITY

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Dummy Activities

A

B

C

D

DUMMY

ACTIVITYPRECEDING

ACTIVITY

A -B -C B D A,B

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19

a c

b d

b precede d

a and b precede c

a

b

c

d

e

a and b precede d

a,b, and c precede e

Dependencies

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a

b

c

d

e

a

b

c

d

e

Dependencies

d depends on a and b

c depends only on a

e depends only on b

d depends on a and b

e depends on b and c

Constructing the Network

1

2

1

a

b

c

d

e

a

b

e

c d

WRONG RIGHT

1

2

3

a

b

c

d

e

f

1

42

3

a d

b

c f

e

a,b,c must precede d, but only a,b precede e

a precede d

a and b precede d

b and c precede d

WRONGRIGHT21

Estimating Activity Time

PERT (Program evaluation and review technique): A method to analyze the involved tasks in completing a given project, especially the time needed to complete each task, and to identify the minimum time needed to complete the total project.

Optimistic time (a): the minimum possible time required to accomplish a task

Pessimistic time (b): the maximum possible time required to accomplish a task,

Most likely time (M): the best estimate of the time required to accomplish a task

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Expected time (TE): The best estimate of the time required to accomplish a task

TE = (a + 4M + b) / 6

Standard deviations of each activities

= ( b - a ) / 6

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Estimating Activity Time

Crashing the Schedule

If the schedule you develop does not allow the project to complete when desired, you might have to take action to decrease the total project duration.

This is known as crashing the schedule.

You need to look at options in areas such as:

Resources

Activities

Project Objectives.

Look for options that give the greatest compression at the lowest costs.

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Schedule Compression

Elimination of some parts of the project

Addition of more resources

Substitution of less time-consuming components or activities

Parallelization of activities

Shortening critical path activities

Shortening early activities

Shortening longest activities25

Schedule Compression

Shortening easiest activities

Shortening activities that are least costly to speed up

Shortening activities for which you have more resources

Increasing the number of work hours per day

(Continued)

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Resource Leveling

Resource leveling is an attempt to eliminate the manpower peaks and valleys by smoothing out the period-to-period resource requirements.

The ideal situation is to do this without changing the end date. However, in reality, the end date moves out and additional costs are incurred.

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Resource Allocation

Resource allocation (or resource limited planning) is an attempt to find the shortest possible critical path based upon the available or fixed resources.

The problem with this approach is that the employees may not be qualified technically to perform work on more than one activity in a network.

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Activity to Construct a Pump Station

Activity Activity description Duration ,daysImmediate

Predecessors1 Start 02 Mobilise 2 13 Survey 1 24 Grade site 2 25 Trench footings 5 3,46 Form and pour concrete 5 5,87 Cure concrete 8 68 Concrete and material design 5 19 Spec prefab metal building 4 1

10 Plumbing materials, pump 5 111 Electrical materials, lights, panel 5 112 Install pump 7 7,9,1013 Erect structural steel 4 7,9,1014 Install roofing and siding 5 1315 Install lights and panels 3 11,1416 Test Pump 2 1217 Paint 3 1518 End 0 16, 17

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Classroom Activity 6a

Draw a network diagram using the details in the previous slide.

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Precedence Network

TASKS 1 2 3 4 5

4

MONTHS AFTER GO-AHEAD

3

2

1

5

The interrelationships on bar charts

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Types Of Precedence Charts

ACTIVITY 1

ACTIVITY 1

ACTIVITY 2

ACTIVITY 2FINISH-TO-START

START-TO-START

FINISH START

START

START

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ACTIVITY 1

ACTIVITY 1

ACTIVITY 2

ACTIVITY 2

FINISH-TO-FINISH

PERCENT COMPLETE

FINISHFINISH

20 %

50 %

Types Of Precedence Charts

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EARLY START01/06/97

TIME DURATION2 WORK-WEEKS

EARLY FINISH14/06/97

ACTIVITY 4

TOTALSLACK(TS)

$250,000

LATE START15/06/97

COST/PROFIT CENTER 2810

LATE FINISH28/06/97

FREE SLACK(FS)

ACTIVITY INFORMATION

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Questions?