LECTURE 6Scheduling 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

interdependenciesofactivities

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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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GanttChart Example

JobDay 1

Day 2

Day 3

Day 4

Day 5

Day 6

Day 7

Day 8

Start of an activity

A

BMaintenance

C

Now

End of an activity

Scheduled activity time allowed

Actual work progress

Nonproduction time

Point in time when chart is reviewed

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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 arrow11

AON: Activities On the Node

AOrder Pipe

C

Deliver Pipe

Start

B

D

Lay Pipe

Finish

Dig Trench

Precedence Diagram Method12

AOA: Activities On the Arrow

ACTIVITY633 WEEKS

COMPLETE TESTINGCOMPLETE FINAL REPORTLEGEND

EVENT 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

3131

2618

1826

77

BURST POINTSINK

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Dependencies

aadebb1eccd

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

WRONGRIGHT

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Simplified PERT Network

3

12567894

LEGEND: (TIME = WEEKS) EVENTACTIVITYCRITICAL PATH ACTIVITY

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Dummy Activities

D

AACTIVITY

PRECEDING ACTIVITY

DUMMY

BCA -B -C BD A,B

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Dependencies

a c

b precede db da and bprecede c

ada and b precede dbcea,b, and c precede e

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Dependencies

a cd depends on a and bc depends only on ade depends only on bb e

add depends on a and be depends on b andcb

ce

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Constructing the Network

aead1bb1WRONGRIGHTeccd2a,b,c must precede d, but only a,b precede e

a d1a precede da and bb eprecede d2b and c precede dc f3WRONGa d1

b e24

c f3RIGH21T

EstimatingActivity 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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EstimatingActivity Time

Expected time (TE): The best estimate of the time required to accomplish a taskTE = (a + 4M + b) / 6 Standard deviations of each activities = ( b - a ) / 6

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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

(Continued)

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

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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

ActivityActivity descriptionDuration ,daysImmediate Predecessors

1Start0

2Mobilise21

3Survey12

4Grade site22

5Trench footings53,4

6Form and pour concrete55,8

7Cure concrete86

8Concrete and material design51

9Spec prefab metal building41

10Plumbing materials, pump51

11Electrical materials, lights, panel51

12Install pump77,9,10

13Erect structural steel47,9,10

14Install roofing and siding513

15Install lights and panels311,14

16Test Pump212

17Paint31529

18End016, 17

Classroom Activity 6a

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

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Precedence Network

The interrelationships on bar charts

MONTHS AFTER GO-AHEAD TASKS123451234531

Types Of Precedence Charts

FINISHSTART

FINISH-TO-START

ACTIVITY 1

ACTIVITY 2

START

START-TO-START

ACTIVITY 1

START

ACTIVITY 2

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Types Of Precedence Charts

FINISH-TO-FINISH

PERCENT COMPLETE

FINISHACTIVITY 1

ACTIVITY 1

FINISH

ACTIVITY 2

50 %

20 %ACTIVITY 233

EARLY START 01/06/97TIME DURATION 2 WORK-WEEKSEARLY FINISH 14/06/97ACTIVITY 4TOTAL SLACK(TS)$250,000FREE SLACK (FS)LATE START 15/06/97COST/PROFIT CENTER 2810LATE FINISH 28/06/97ACTIVITY INFORMATION

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Questions?

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