Project Management Techniques ( WBS & Critical Path Method )

Construction Management
and Entrepreneurship
By,
Prof. Surajkumar S Sonar
Veerapa Nisty Engineering College
Department of Civil Engineering

Project management
Project management is a distinct area of management that
helps in handling projects.
It has three key features to distinguish it from other forms of
management and they include:
A project manager, the project team and the
project management system.
The project management system comprises organization
structure, information processing and decision making and
the procedures that facilitate integration of horizontal and
vertical elements of the project organization.
The project management system focuses on integrated
planning and control.
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Department of Civil Engineering, VNEC,
Shorapur

Work Breakdown Structure as a "hierarchical
decomposition of the total scope of work to be carried
out by the project team to accomplish the project
objectives and create the required deliverables."
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In a WBS, the deliverable can be an object, a service, or
an activity.
By focusing on deliverables rather than methods — the
what, not the how — a work breakdown structure
helps eliminate unnecessary work to get the intended
result.
A well-thought-out WBS aids in scheduling, estimating
costs, and determining risk.
It is usually a visual chart or diagram that spells out a
project's timeline and process while capturing each
task, subtask, and deliverable that will be created and
executed throughout.
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Here are some of the advantages and benefits of creating a WBS:
 Provides a visual representation of all parts of a project
 Offers an ongoing view for management and team members
into how the entire project is progressing
 Defines specific and measurable outcomes
 Breaks the work into manageable chunks
 Provides a way to make successful experiences repeatable
 Sets a foundation for estimating costs and allocating human
and other resources
 Ensures no overlap and no gaps in responsibility or resources
 Minimizes the chance of adding items outside the scope of
work or forgetting a critical deliverable.
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In addition,
By taking into account each project’s WBS, the organization can
quickly calculate the budget for whole departments.
Teams can determine project schedule and budget quickly.
As the project progresses, teams can track specific sections of the
work breakdown structure to determine project cost
performance and flag issues and problem areas in the
organization.
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A well-crafted work breakdown structure can keep your
team humming along like a well-oiled machine with
these benefits:
 Improves productivity
 Helps project managers predict results based on
various scenarios
 Helps with project organization
 Assists in describing the project scope to stakeholders
 Helps to distribute responsibilities
 Allows correct estimation of costs, risks, and time
 Increases communication
 Enables more creativity and brainstorming
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 Focuses on end goals
 Organizes details
 Potentially prevents problems
 Addresses scheduling issues
 Helps manage risks
 Allocates tasks
 Gives teams flexibility
 Eliminates confusion
 Gives every team member clear task descriptions
 Helps write and support the statement of work
 Provides foundation for clear status report on project,
since each work package is a measurable unit
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Once the project scope is available, the WBS should be
the first deliverable.
With the WBS defined, it’s then possible to scope out
other resources, including human resources,
particular skill sets, material resources (such as
equipment and space), and facilities.
The team can then create the baseline schedule, draw up
task lists, and provide assignments.
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Project Management Techniques
Introduction
Project management involves decision making for the
planning, organizing, coordination, monitoring and
control of a number of interrelated time bound
activities.
Project Manager therefore, often depends on tools and
techniques that are effective enough not only for
drawing up the best possible initial plan but also capable
of projecting instantaneously the impact of deviations so
as to initiate necessary corrective measures.
These project management techniques can be classified
under two broad categories i.e., Bar Charts and
Networks.
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Bar Charts
Bar charts are the pictorial representation of various tasks required to
be performed for accomplishment of the project objectives.
These charts have formed the basis of development of many other
project management techniques.
Gantt Chart
Henry L Gantt (1861 – 1919) around 1917 developed a system of bar
charts for scheduling and reporting progress of a project. These
charts latter were known as Gantt Charts.
It is a pictorial representation specifying the start and finish time for
various tasks to be performed in a project on a horizontal time-scale.
Each project is broken down to physically identifiable and
controllable units, called the Tasks.
These tasks are indicated by means of a bar, preferably at equi-distance
in the vertical axis and time is plotted in the horizontal axis.
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A Gantt chart is constructed with a horizontal axis
representing the total time span of the project, broken
down into increments (for example, days, weeks, or
months) and a vertical axis representing the tasks that
make up the project (for example, if the project is
outfitting your computer with new software, the
major tasks involved might be: conduct research,
choose software, install software).
Horizontal bars of varying lengths represent the
sequences, timing, and time span for each task.
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Using the same example, you would put "conduct
research" at the top of the vertical axis and draw a bar on
the graph that represents the amount of time you expect
to spend on the research, and then enter the other tasks
below the first one and representative bars at the points
in time when you expect to undertake them.
The bar spans may overlap, as, for example, you may
conduct research and choose software during the same
time span.
As the project progresses, secondary bars, arrowheads, or
darkened bars may be added to indicate completed tasks,
or the portions of tasks that have been completed.
A vertical line is used to represent the report date.
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Advantages of Gantt Charts
It creates a picture of complexity.
It organizes your thoughts.
It demonstrates that you know what you’re doing.
It (should) help you to set realistic time frames.
It can be highly visible. .
Disadvantages of Gantt Charts
They can become extraordinarily complex.
The size of the bar does not indicate the amount of work.
They need to be constantly updated.
Difficult to see on one sheet of paper.
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Networks
The network is a logical extension of Gantt’s milestone
chart incorporating the modifications so as to
illustrate interrelationship between and among all the
milestones in an entire project. The two best-known
techniques for network analysis are Programme
Evaluation and review Technique (PERT) and
Critical Path Method (CPM). These two techniques
were developed almost simultaneously during 1956-
1958.
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PERT was developed for US navy for scheduling the
research and development activities for Polaris
missiles programme. CPM was developed by E.I. du
Pont de Nemours & Company as an application to
construction project.
Though these two methods were developed
simultaneously they have striking similarity and the
significant difference is that the time estimates for
activities is assumed deterministic in CPM and
probabilistic in PERT.
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There is also little distinction in terms of application of
these concepts.
PERT is used where emphasis is on scheduling and
monitoring the project and CPM is used where
emphasis is on optimizing resource allocation.
However, now-a-days the two techniques are used
synonymously in network analysis and the differences
are considered to be historical.
Both CPM and PERT describe the work plan of project
where arrows and circles respectively indicate the
activities and events in the project. This arrow or
network diagram includes all the activities and events
that should be completed to reach the project
objectives. The activities and events are laid in a
planned sequence of their accomplishments.
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However, there are two types of notations used in the
network diagram.
They are as under,
1. Activity-on-Arrow (AOA), and
2. Activity-on-Node (AON).
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AOA diagram
AOA diagram is drawn using circles as the nodes,
with nodes represents the beginning and ending
points of the arrows or tasks.
Arrows act as activities or tasks in AOA diagram. Even
though AOA is a good approach to draw a network
diagram, it has its own drawbacks too.
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The following are the drawbacks of AOA
network diagram conventions identified
by Taylor (2008):
The AOA network diagram can only show
Finish to start relationships. It is not
possible to show lead or lag time except
by adding or subtracting time. This makes
project tracking difficult.
There are instances where "dummy
activities" can occur in AOA diagram.
(dummy activities are activities which
does not have duration but simply there to
show dependency of one task on other
task)
AOA networks are not supported by many
software tools, thus it is not widely used.
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AON diagram
AON network diagram is where circles are used to represent
an activity, with arrows linking them together to show the
sequence in which they are performed. The following are
the advantages of AON network diagram identified by
Taylor (2008):
AON does not have dummy activities as the arrows represent
only dependencies.
AON can accommodate any types of relationship ( Finish to
Start, Finish to Finish, Start to Start, Start to finish, Lead
and Lag)
AON is widely as it is supported by almost all the project
management software tools
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Activity: A recognizable work item of a project
requiring time and resource for its completion.
Dummy Activity: An activity that indicates precedence
relationship and requires no time nor resource.
Critical Activity: Activities on the critical path having
zero slack / float time.
Event: An instantaneous point in time signifying
completion or beginning of an activity.
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Burst Event: An event which gives rise to more than
one activity.
Merge Event: The event which occurs only when more
than one activity is accomplished.
Earliest Start Time (EST): The earliest possible time at
which the event can occur.
The EST of an activity is the time before which it cannot
commence without affecting the immediate preceding
activity.
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Latest Start Time (LST): The latest time at which the
event can take place. (latest time at which an activity
can begin without delaying the project completion
time)
Slack: The amount of spare time available between
completion of an activity and beginning of next
activity.
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Steps for Network Analysis:
The six steps of network analysis are as follows.
1. Prepare the list of activities
2. Define the inter relationship among the activities.
3. Estimate the activity duration
4. Assemble the activities in the form of a flow diagram
5. Draw the network
6. Analyze the network i.e. compute EST and LST;
identify critical events, critical path and critical
activities.
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Rules for Drawing the Network:
1. Each activity is represented by one and only one arrow in the
network
2. All the arrows must run from left to right.
3. Dotted line arrows represent dummy activities.
4. A circle represents an event.
5. Every activity starts and ends with an event.
6. No two activities can be identified by the same head and tail event.
7. Do not use dummy activity unless required to reflect the logic.
8. Avoid Looping and crossing of activity arrows by repositioning.
9. Every Activity, except the first and the last, must have at least one
preceding and one succeeding activity.
10. Danglers, isolated activities must be avoided.
11. For coding use alphabets for all activities including the dummy
activity and numbers for events.
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Critical Path Method:
Critical path schedules will...
Help you identify the activities that must be completed on
time in order to complete the whole project on time.
Show you which tasks can be delayed and for how long
without impacting the overall project schedule.
Calculate the minimum amount of time it will take to
complete the project.
Tell you the earliest and latest dates each activity can start
on in order to maintain the schedule.
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The Critical Path Method has four key elements...
 Critical Path Analysis
 Float Determination
 Early Start & Early Finish Calculation
 Late Start & Late Finish Calculation
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Critical Path is the sequence of activities with the
longest duration.
A delay in any of these activities will result in delay of
the hole project.
Float (slack) is the amount of time that a schedule
activity can be delayed or extended from its early start
date without delaying the completion of the project.
Find all the paths from start to end of a project using
network diagram.
Calculate the total duration of each paths separately.
Path with the longest duration will be the Critical Path.

CPM helps the managers as,
 It demonstrates the graphical view of any project.
 It helps to identify the most important tasks that you
have to manage.
 It helps to save your time and reduce timelines.
 It helps to compare planned and actual progress.
 It helps to make dependencies visible and clear.
 It helps to plan, schedule and control your projects.
 It helps to identify all critical activities that need your
special attention.
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Float Determination
Start with the activities on the critical path.
Each activity in critical path will have a float equals
to zero.
Then, Choose the next longest path.
Subtract its duration from the duration of the critical
path.
Continue for other longest paths until you fond float
for all activities.
If any activity has two floats then, its float will be
based on the longer path that it belongs to.

Early Start ( ES ) and Early Finish ( EF )
Forward Pass.
It is used to determine the earliest date an activity can
start and the earliest date it can finish.
Start with the critical path.
Early Start of the first activity is one (1).
Early Finish of an activity is its ES + its duration – 1 .
Then move to the next activity in the path*
*ES of the present activity if EF of previous activity + 1
EF is calculated same as before.
If the activity has more than one predecessor, to
calculate ES use EF of latest activity / higher value.
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Late Start ( LS ) and Late Finish ( LF )
Backward Pass.
Latest time an activity can start or can be finished without
effecting the project completion.
Start from the last activity in the critical path.
For the last activity in the critical path, LF is equal to its EF.
LS = LF – its duration + 1
Move on to the next activity in the critical path.
Its LF = LS of previous activity – 1
Its LS is calculated as LF – its duration + 1.
Continue the process.
IF you get two LF s for the same activity use lower value.
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Activity Duration
in Days
A) Lay Foundation 7
B) Build walls 10
C) Lay drains and floors 15
D) Install fittings 8
E) Make and fit door
frames
2
F) Erect roof 5
G) Plaster ceiling 2
H) Fit and paint doors and
windows
8
I) Fit gutters and pipes
J) Paint Outside
2
3
B must be after C
C must be after A
D must be after B
E must be after C
F must be after D and E
G must be after F
H must be after G
I must be after F
J must be after H
Draw the network diagram.
Find the critical path, float, EST, EFT,
LST and LFT.

A+C+B+D+F+I+J = 7+15+10+8+5+2+3 = 50
A+C+B+D+F+G+H+J = 7+15+10+8+5+2+8+3 = 58
A+C+E+F+G+H+J = 7+15+2+5+2+8+3 = 42
A+C+E+F+I+J = 7+15+2+5+2+3 = 34
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A
C B D
E F G H
I
J
7
15 10
2
8
5 2
2
8 3
F = 0
F = 0 F = 0
F = 0
F = 0 F = 0 F = 0
F = 8
F = 16
F = 0

A+C+B+D+F+I+J = 7+15+10+8+5+2+3 = 50
A+C+B+D+F+G+H+J = 7+15+10+8+5+2+8+3 = 58
A+C+E+F+G+H+J = 7+15+2+5+2+8+3 = 42
A+C+E+F+I+J = 7+15+2+5+2+3 = 34
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A
C B D
E
F G H
I
J
7
15 10
2
8
5 2
2
8 3
ES = 1
EF = 7
ES = 8
EF = 22
ES = 23
EF = 24
ES = 23
EF = 32
ES = 33
EF = 40
ES = 41
EF = 45
ES = 46
EF = 47
ES = 46
EF = 47
ES = 48
EF = 55
ES = 56
EF = 58

A+C+B+D+F+I+J = 7+15+10+8+5+2+3 = 50
A+C+B+D+F+G+H+J = 7+15+10+8+5+2+8+3 = 58
A+C+E+F+G+H+J = 7+15+2+5+2+8+3 = 42
A+C+E+F+I+J = 7+15+2+5+2+3 = 34
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A
C B D
E F G H
I
J
7
15 10
2
8
5 2
2
8 3
ES = 1
EF = 7
LS = 1
LF = 7
ES = 8
EF = 22
LS = 8
LF = 22
ES = 23
EF = 24
LS = 39
LF = 40
ES = 23
EF = 32
LS = 23
LF = 32
ES = 33
EF = 40
LS = 33
LF = 40
ES = 41
EF = 45
LS = 41
LF = 45
ES = 46
EF = 47
LS = 46
LF = 47
ES = 46
EF = 47
LS = 54
LF = 55
ES = 48
EF = 55
LS = 48
LF = 55
ES = 56
EF = 58
LS = 56
LF = 58

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Note:
• This information is collected from different sources
for better understanding of the topics.
• Read the text books available on the topics and
practice.
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Thank you..!
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Project Management Techniques ( WBS & Critical Path Method )

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