Wolkite University

Department of CoTM

Lecture 1

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Project planning scope
Contents of the lecture
Plan development Process
Time planning process
Work scheduling process
Resource planning process
Project control process
 Importance of planning,
scheduling and controlling projects

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1. Plan development process
PLANNING process
Planning aims at formulation of a time-based plan of action for
coordinating various activities and resources to achieve
specified objectives. Planning is the process of developing the
project plan. The plan outlines how the project is to be
directed to achieve the assigned goals. It specifies a
predetermined and committed future course of action, based
on discussions and decisions made on the current knowledge
and estimation of future trends.

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Scheduling means putting the plan on a calendar time scale.
During execution stage, monitoring brings out the progress
made against the scheduled base line. Control deals with
formulation of and implementation of corrective actions
necessary for achieving project objectives. In the construction
phase of project development, planning and controlling are in
separable. During project implementation, the plan-do-
monitor-communicate re-plan(when necessary) is a
continuous processes. In this context , the term planning
broadly includes the plan-making, scheduling and controlling
processes. (E.g. project management process, relation and
interaction of the process groups)

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• Process involved in construction planning can
broadly be divide in two;

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• The construction planning process is stimulated through the study
of documents.
• These documents include-but not limited to;
 The available technical and commercial studies and investigations
 Designs and drawings
 Estimate of quantities
 Construction method statements
 Project planning data
 Contract documents
 Site conditions
 Working regulations
 Market survey
 Local resource
 Project environment and,
 The client’s organization
The planning process takes into account the strengths and weakness of
the organization as well as the anticipated opportunities and risks.

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• Planning follows a systematic approach. Various planning techniques are employed to
systematize and transform the mental thought process into a concrete project plan.
Project Planning Process

Planning data collection Where to look for data? Studying the relevant documents
Planning time What is to be done? Define scope of the work
What are the activities involved? Breakdown project into activities
How it can be done? Developing network plans
When it is to be done? Scheduling work
Where it is to be done? Charting site layout

Planning resource What is needed to do it? Forecasting resource requirement

Planning the 4M’S
Who is to do it? Designing organizational structure
Allocate tasks and resource
Establishing responsibility centers
Planning implementation How to account performance? Designing control systems
How to monitor performance? Formulating monitoring methodology

How to communicate information? Developing project management

information system(PMIS)

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Project Planning Techniques
Stages Planning process Techniques/methods

Planning time Breaking down project work Work breakdown

Developing time network plan Network Analysis, BC&LOB

Scheduling Time limited scheduling

Resource limited scheduling
Planning resources Forecasting resource requirement Forecasting
Planning manpower requirement Manpower scheduling
Planning materials requirement Materials scheduling
Planning equipment procurement Equipment selection and
scheduling
Budgeting costs Cost planning and budgeting
Designing organizational structure Organization design
Allocating tasks and resources Resource allocation
Planning Formulating monitoring methodology Resource productivity control
implementation Time control
Contribution control
Budgetary control

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Types of project plans
Planning the entire project from its inception to completion requires
a vast coverage, varied skills, and different types of plans. The nature
of plan encountered in a typical construction projects are;

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• Project feasibility plan
Planning by the client begins as soon as he gets the
idea about developing the facility to fulfill certain
motives. His early thought process conceptualize the
cost, time and benefit implications of the project. Only
when he is convinced about the soundness of his idea
does, he decide to go ahead with the feasibility
studies.
The feasibility study team examines the needs of the
client and ways to fulfill them. It defines the over all
scope of work, and assess the time and costs of
accomplishing the project. This outline plan, developed
by the feasibility team during inception stage, forms
the basis for identifying projects objectives and
developing the project plan.
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• Project preliminary plan

Acceptance of the feasibility studies marks the commencement of

the preliminary plan-making process. It main aim is to provide
direction to the client mangers and staff employed during the
development phase of the project. The project preliminary plan
forms the basis for developing the project construction plan. The
preliminary plan includes;
 A project time schedule and skeleton network to highlight the work
dependencies, project milestones and the expected project
completion time
 The project design and drawings preparation schedule
 A breakdown of project work into contracts, along with a schedule
of contracting activities, including the tender preparation period,
tender finalization period, and the contracted works
commencement and completion dates.
 A resource preliminary forecast indicating the phased requirements
of men, important materials, plant and machinery.
 Resource procurement system
 Project organization and staffing pattern
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 Preliminary forecast of funds requirement
• Project construction plan
the project construction plan includes;
Time plan it depicts the schedule of project
activities for completion of the project within the
specified time.
Resource plan it forecasts the required input
resources of men, Machinery and money for achieving
the project completion time target and cost objective.
Plan for controlling project  it encompasses the
design of control system, monitoring system,
codification system and the computerized information
system.
• The construction projects plan development
process is divided into three parts; time planning,
resource planning and project control system
planning. These parts are interdependent and not
mutually exclusive. 12
 2. Time planning process
• A plan prepared well before the commencement of construction in
a project, can be instrumental in formulating directions,
coordinating functions, setting targets, forecasting resources,
budgeting costs, controlling performance and motivating people.
However, the absence of a project time plan almost makes certain
that a project can not be completed on schedule without incurring
extra costs.(Benefit of planning)
• The time planning process involves the following three stages;
(a) Project work breakdown this means breaking down the scope of
project work into its constitute sub-projects, tasks, work packages
and activities.
(b)Modeling and analyzing networks this include developing logic
diagrams or sub-networks; integrating these to develop a time-
planning model(Usually a network), and; analyzing this model to
determine the project completion time.
(c) Scheduling work programme this involves putting the time plan
on a calendar basis, and using the scheduled programme to
forecast inputs and out puts.

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 3. Work scheduling process
• Scheduling means putting the plan on calendar basis. A project
network shows the sequence and interferences of activities, their time
durations and earliest and latest completion time, but this needs to be
scheduled to determine commence and termination dates of each
activity, using optimum resources or working within resource
constraints. A time schedule outlines the project work programme, it
is a time table of work.

• Scheduling procedure
 The scheduling methodology varies with the planning techniques and
the nature of the task to be performed. A tool containing the
commonly used techniques for planning, scheduling and monitoring is
indicated in the next slide.
 Each Scheduling Techniques has its own merits and demerits. But
ultimately scheduling are best presented in the bar chart form for
ease of comprehension and communication. These bar charts are
supplemented with appropriate planning technique for monitoring
the progress of the projects.
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 Commonly used time planning techniques in
construction project management
SI.N Nature of the project Planning Scheduling Monitoring Displaying
O

Simple project/sub
1 project
(a)Non-repetitive work Bar Chart Bar Chart Bar Chart Bar Chart
(b)Repetitive work
LOB LOB LOB LOB/Bar chart

2 Complex sub-projects
(a)Deterministic Time scale
(b)Probabilistic
CPM Bar Chart
PERT Network CPM
>> PERT >>

3 Complex Projects
(a)Non-repetitive W. PNA Bar Chart PNA Bar Chart
(b)Repetitive work PNA LOB LOB Bar Chart/LOB
(c)Probabilistic PERT Time Scale network PERT Bar Chart

CPM-Critical Path
PERT-Programme Evaluation and Review Techniques BC-Bar Chart
PNA- Precedence Network Analysis TSN-Time Scale Network/Logic Bar Chart
LOB-Line of Balance 15
• The scheduling procedures, depending upon
type of project can be broadly divided into
two categories;
1.Scheduling non-repetitive network based
projects
2.Scheduling repetitive projects using line of
balance techniques

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1. Procedure for Scheduling non-repetitive network
based projects
 Outline scheduling constraints
 Design scheduling calendar
 List activities in order of sensitivity
 Draw earliest start time schedule
 Determine resource optimization criteria
 Schedule critical activities
 Schedule non-critical activities
 validate time objectives
 Schedule other resource
 Schedule within resource constraints
 Schedule repetitive work projects

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2. Procedure for Scheduling repetitive projects
using line of balance techniques
 Outline schedule constraints
 Tabulate scheduling data of a unit work cycle
 Prepare a logic diagram of a unit work cycle
 chart scheduling calendar
 Prepare earliest start time schedule
 Analyze earliest start time schedule
 Prepare optimum schedule leaving adequate
buffer
 Draw Line-of-Balance work schedule

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 4. Resource planning Process
• Forecasting inputs and outputs
The inputs and output forecast includes the data-wise requirement of project
manpower, major materials, costly equipment, production costs, earned value of
work done and the expected income. The basis of forecasting is the schedule of
work.
 Inputs and outputs forecast aids in conceptualization of project. It indicates the
quantum of resources required for executing is project the output expected. The
pattern of input resource form the base for evaluating such needs as workers’
accommodation, materials storage, equipment work-load and project funding
pattern.

• Planning construction work force

the project manpower planning primarily focuses on determining the size of the
project work force, its structuring into functional groups and workers’ teams, and
scheduling the manpower recruitment/induction to match the task requirements.
 This process chiefly involves identifying the trades or the skills required,
establishing productivity standards to determine the number of workers needed
to perform a given job in the specified time, data-wise forecasting of the workers’
requirements for accomplishing the project work, and , finally, organizing the
planned workforce into operating work-teams having assigned programmed tasks.

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 Resource planning Process
• Planning construction materials

the construction materials planning involves identifying the materials

required, estimating quantities, defining specifications, forecasting
requirements, locating sources for procurement, getting material samples
approved, designing materials inventory, and developing the procurement
plan to ensure a smooth flow of materials till the connected construction
works are completed at the project site.

• Planning construction equipments

 Equipment planning for a project aims at identifying the construction
tasks to be undertaken by mechanical equipment, assessing the
equipment required, exploring the equipment procurement options and,
finally, participating in the decision-making for selecting the equipment

• Planning construction standard costs & planning construction Budgets.

the construction cost plan uses standard cost concept for costing work-
packages, work items or activities. The standard cost technique finds wide
applications in estimating, forecasting, budgeting, accounting and
controlling costs.
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 5. Project Control Process
• Control involves organizing the control responsibility centers,
designing accounting and monitoring methodology, codifying data
and developing the information system so as to make-decisions
speedily. It also includes identifying the problem areas, making risk-
taking decision to tackle the problem, organizing and directing
resources needed to carry out these decisions, and measuring the
results of these decisions against targeted expectations through
organized and systematic feedback.

• An efficient control system improves productivity of men and

materials, economizes employment of resources, enables
understanding of time and cost behaviors, provides yard-stick for
measuring performance, generates information for updating
resource planning and costing norms, prevents pilferage and frauds
and assists in formulating bonus or incentives scheme for
motivating people.

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•
Project
Project control Methodology
Control Process
the project control follows the system concept. Each organizational unit in a project,
usually referred to as the responsibility center, can be viewed as a sub-systems are
highly interdependent and interactive. The performance objective of a sub-system are
stated in terms of the parameters to the controlled. These parameters include the time
progress targets, resource productivity standards and the work-package standard costs
and sales target. Each sub-system accounts for its performance and reports its actual
performance to the monitor. And it is these reports that serve as early warning signals
of ensuing dangers.
• Control resource productivity
productivity control aims at ensuring efficient utilization of inputs of men, materials and
equipments by identifying cases of their wastage as well as affecting improvement to
minimize it. The case of wastage are located by analyzing variances and efficiency of
planned and on-site actual productivity;
Productivity performance variance=planned productivity-actual productivity
Productivity performance index=planned productivity/actual productivity

The methodology used for controlling the parameters (Labor productivity, equipment
productivity and material productivity) can be divided into four stages;
Defining the control purpose, measuring the actual performance, computing the
productivity performance variance and identifying their causes for effecting
improvements.

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 Project Control Process
• Control Costs
It involves the processing of reports received from various
responsibility centers or operating divisions, relating the costs
incurred with the set standards, analyzing the reason for any
variances and presenting the results to the project management for
decision-making and initiating remedial measures.
• Controlling time
the project time control aims at timely execution of work as per the
work programme and applications of corrective measures in case of
deviations.
 The time control process involves the monitoring of time status by
updating the project network and time schedules, reviewing
durations of balance activities, computing deviations and evaluating
the implication of deviations on project time objective by time-
analyzing the project network. It includes formulating remedial
measures including what-if analysis, time crashing, re-planning, re-
forecasting and re-mobilizing resources under changed situations
with a view to accomplish the time objective.
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6.Importance of planning , Scheduling and controlling
projects
• Planning benefit
 Project plan clearly defines project scope of work. It breaks down project
objectives into clear, identifiable, quantifiable, attainable and verifiable
goals which are assigned to individuals and responsibility centers for
accomplishment.
 Project plan aids the management in performing its functions efficiently
and effectively.
 Project plan forms the basis of a project operations and directions and
shows how the project is to be run. It also specifies the committed future
course of actions on the basis of current decision made with available
knowledge of future.
 Project plan identifies critical activities, thus enabling the managing of
project by exception.
 Project plan provides the yard-stick for measuring progress and evaluating
resources performances
 project plan has build in flexibility in the form of floats, to navigate
changes in the planned path for meeting fast changing environment.
 Project plan creates healthy environment. It promotes unity of purpose
among functional diversities to make people time and cost conscious. It
commits individuals to asks and motivates them to achieve challenging
targets. 24
Importance of planning , Scheduling and controlling
projects
• Schedule Benefits
 Schedule simplifying a project plan.
 Schedule validates time objective. work
schedule shows the planned sequence of
activities, data-wise.
 Schedule aid in optimization of resource
employed.
 Schedule enables forecasting of input resources
and earned value to indicate the pattern of
requirement and the financial state of the project
in terms of investment, expenditure, output and
income.
 Schedule brings out implication of time and
resource constraints. 25
 Importance of planning , Scheduling and controlling
projects
• Control Benefit
 The control system aids the management at various levels to perform its
functions efficiently and effectively for achieving the overall project objectives.
 The benefits which can be derived at each level of management through an
effective control system are;

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• Operational control at Supervisory Level

In improves productivity by;

 Minimize unproductive man hours
 Preventing wastage of materials
 Economizing plant and machinery utilization
 Reducing activity execution time

• Administrative control at managerial level: it assists in ensuring project

organization efficiency and effectiveness by;

updating the work quantities status and determining the balance scope of
work
analyzing project time status and its implication on project time objectives.
evaluating production cost status and forecasting future trends.
calculating income status and forecasting cash inflows
computing budget status and forecasting cash inflows
 Computing budgets status and analyzing the implication of variance of
future expenditure.

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• Directional control at general manager's/ project manager’s level

It helps in formulating and directing polices for achievement of project

objectives
 Analyzing project time cost behavior and making decisions on time saving
when required
 Reviewing project costs and profitability, and making profitability
improvement decisions concerning wastage reductions through rigorous
cost control, value engineering techniques, cost benefits analysis, workers
incentive schemes and alternate methods of construction which cost less.

• Strategic control at corporate level

It provides information concerning corporate goals and assistance in
formulating corporate strategies by;

Determining overall profitability

budgeting and allocating funds and resources.
 Updating the company’s planning norms and unit rates for securing future
works.

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Lecture-2
Chapter two(Time planning)
Project work Breakdown
Project Network Analysis (part I
CPM&PERT)

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 Project work Breakdown
Project work-breakdown methodology enables
splitting of the project work into hierarchical
work-breakdown levels of;
 sub-projects
 tasks
 Work packages
 Activities
Each activity represents an identifiable lower-level
job which consumes time, and possibly resource.
Construction projects are best organized by tasks into
task responsibility centers. They are best managed by
work packages and best planned and mentored by
activities.

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 Project work Breakdown levels
the project work-breakdown process involves breaking
down of the project work into manageable parts arranged
in a hierarchical order till the desired level is reached.
work-breakdown levels;
 Sub-project level-Mini project/task groups
 Tasks level-a task is an identifiable and deliverable major work, is used
in the project-summary plan, the design-Preparation plan and the
contract tendering plan.
 Work package level-Each work package contains a sizable, identifiable,
measurable, costable and controllable package of work. In the project
master plan or the contracted works-plan, each work package is
assigned its performance objective. These are generally stated in
terms of its completion period, standard cost and resource
productivity standard.
 Activity level
 Operational level
the work breakdown structure of a project forms the basis
for listing of activities, modification of systems, storing data
by hierarchy levels, structuring of work organization and
managing similar-scope multi-projects 31
 Mega project
Real Estate Development
(Programme)

Residential Buildings Service Buildings Recreation Centers

Sub projects

Educational Buildings Health Centre Shopping centre

Tasks
Sub structure Super Structure Roofing Finishing

Base construction Footing Con Plinth wall Con Ground floor Con Work package

Earth work Base preparation Blinding

Activities
Layout Excavation Leveling/
compacting
• Example, Operation involved in concreting
are;
Cleaning and preparing inner side of the raft for
concreting
Pumping concrete
Spreading and vibrating concrete
Finishing of top concrete surface

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 Assessing Activity Duration
Duration of an activity is defined as the expected economical
transaction time. The estimation of time is based upon the current
practices carried out in an organized manner under the normal
prevailing conditions, and its assessment is done preferably, by the
person responsible for its performance.
 duration estimation is based on current practices this implies
that the estimation is based on the present knowledge of the
method of transaction in an economical way; it may undergo a
change with the passage of time or with improved techniques.
 Under normal prevailing site condition using economical resource
 activity is Performed in an organized manner  breaking down
activity into elements, matching optimum resource for each
elements, laying down a systematic way method of execution,
specifying objectives and assigning responsibility .
 Responsible person this makes the duration estimate realistic
and meaningful.

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the construction activity accomplishment process combines resources: men,
materials, and machinery. the first step in duration estimation is the methodology
to be used for transforming these input resources into the desired activity.  the
method of choosing and combining these resource may vary!
Duration Estimation methods
1. one time estimate
the estimation of duration is based on one of the following;
i. Planning data
ii. Past experience or execution of a similar project
iii. Average time assessed by a group of executives.
2. Three time estimate
 When the exact duration of an activity, like research and development, is not
certain, the three-times estimate is used to compute its expected duration.
 Application in construction projects -->in certain areas of construction
projects where time is the main criterion and the resources employed are
of secondary consideration;

Te=[To+4Tm+Tp]/6 To, everything goes extremely well with

no delays, Tp everything goes wrong

 Application in Construction Projects

1. Planning of the projects especially, at the feasibility stage
2. The Skelton networks enclosed with the tender documents.
3. The contracted works, where time is the main consideration for management 35
4. The complex structures, where the exact duration estimate is difficult to assess.
3. Trapezoidal distribution estimate
in practice, the profile of most activities takes the
shape of trapezoidal distribution. The build-up and
rundown phase can be expressed in terms of total
activity duration.

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Duration Estimation procedure
Estimating the quantity of work
Deciding the labor and material constants
Assessing the effective activity-wise
employment of resource
Estimate the activity completion period

Completion period=Quantity of work/[output per unit of resource x

resource earmarked]
t=Q/(nXp)

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Network analysis
CPM-> is best suited for activities with
deterministic single-time duration
PERT->useful for project feasibility reports or
tasks involving uncertainties.
PN->commonly used technique for time planning
of construction projects.

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 CPM Network analysis Fundamentals
Network elements
•Event or Milestone
–A point in time when certain conditions have been fulfilled,
such as the start or completion of one or more activities
–Unlike an activity, does not consume time or resources
–Hence, expresses a state of being
–Activities take place between events
•Activity
–An item of work that consumes time and resources to
produce some result

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 Dummy Activity
• This activity does not involve
consumption of resources, and therefore
does not need any time to be
‘completed’.
• It is used to define interdependence
between activities and included in a
network for logical and mathematical
reasons as will be shown later.

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Illustration of event, activity, and dummy activity

A B

10 30 50

C D

20 40 60

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• Critical Path
– The series of activities all of which must finish on
time for the whole project to finish on time
– Sometimes described as the longest path through
a network, hence the shortest project time
– A critical path has zero float
– A critical path assumes that the network logic is
sound

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• Float or Slack Time
– The additional time available to complete a non-
critical activity
• Leads and Lags
– An imposed modification of the logical
relationship between activities
– To accelerate or delay the apparent natural order

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Illustration for TF, IF, and FF
calculation

T.F
TLi Duration TLj

Duration
I.F
TEi TEj
Duration F.F

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 Total Float
• Total Float in an activity (i,j) [TF(i,j)]
• Total float is the amount of time by which the
start of an activity may be delayed without
causing a delay in the completion of the
project. This is calculated as (TF(i,j) = [LST(i,j)]–
[EST(i,j)]) or ([LFT(i,j)]– [EFT(i,j)])

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 Free Float
• Free float is the amount of time by which the
start of an activity may be delayed without
delaying the start of a following activity.
• Free Float = (Earliest start time of the
following activity – Duration of the activity –
Earliest start time of the activity) that is Free
Float = TEj- TEi -D

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 Independent Float
• It is defined as the difference in Total Float
and Free Float. In other words: Interference
Float= Total Float – Free Float.

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Network Preparation
tabulate the network logic drawing the arrow diagrams step-by-step.
Logic activity can be tabulated as
-> which activity/ies preceded & Succeed this activity?
->Are there any logical constraints imposed on this activity?
->Is it the final activity?

Example
Activity Preceding Succeeding Remarks
A - B,H
B A G,J
C - H
D - E,G
E D F
F E - Last activity
G B,D - Last activity
H A,C J
J B,H - Last activity 48
Logic diagram of activities
B
G
A
C H J

D E F

Rearrange to avoid crossing of arrows, inserting events to mark the start

and completion of activities and writing the duration of each activity.
E
2 F
1
D G
5
3
A B J
4 3
C 2
H
2
3

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 Numbering Events

B
G
A
C H J

D E F

E
2
1 2 F
1
D G
5 5 8
3
A B J
0 3 4
4 3
C 2
H 7
2 6
3

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 Event Timings, Activity Timings and
Associated Terms
• Start and finish times
• Earliest Start Time of an activity (i,j) [EST(i,j)]
• This is the earliest that the activity (i,j) can be
started, i.e., all the necessary preconditions are met.
• Earliest Finish Time of an activity (i,j) [EFT(i,j)]
• This is the earliest that an activity can be completed.
Mathematically, the relationship can be expressed as
• EFT (i,j)= EST(i,j) + D(i,j)

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• Latest Finish Time of an activity (i,j) [LFT(i,j)]
– the latest time that an activity needs to be
completed in order that there is no delay in the
project completion.
• Latest Start Time of an activity (i,j) [LST(i,j)]
– the latest time when an activity must be started, in
order that there is no delay in the project
completion.

LST(i,j) = LFT(i,j) – D(i,j)

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 Path and critical path
• Any series of activities connecting the starting
point to the finishing point can be said to
define a ‘path’ and indeed in a project having
several activities, several such ‘paths’ can be
identified.
• Among these paths, the ‘critical path’ is
defined as one that gives the longest time of
completion (of the project), which also defines
the shortest possible project time.

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 Forward and Backward Pass
• The forward pass moves from the ‘start’ node towards the
‘finish’ node, and basically calculates the earliest occurrence
times of all events.
• Considering that the project starts at time zero, the earliest
occurrence time at each node is found by going from node to
node in the order of increasing node numbers keeping in
mind the logical relationships between the nodes as shown by
the connecting arrows.
• The earliest occurrence time for any node can be estimated
from the (maximum) time taken to reach that node from the
different incoming arrows.

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 EXAMPLE
Task ID Duration Dependency

A 7
B 3

C 6 A
D 3 B
E 3 D,F
F 2 B
G 3 C
H 2 E,G
55
 Network of the example
C

A
2 6 3 G
3
7
H
A
B D 6 E 7 8
1
4
3 4 3 3 2
F
2
5

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 Network of the example
C
2 6
3
G
A 3
7
H
A
B D 6 E 7 8
1
4
3 4 3 3 2
F
2
5

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 Computations
Act. Duration EST EFT LST LFT TF

A 7 0 7 0 7 0
B 3 0 3 7 10 7
C 6 7 13 7 13 0
D 3 3 6 10 13 7
E 3 6 9 13 16 7
F 2 3 5 11 13 8
G 3 13 16 13 16 0
H 2 16 18 16 18 0 58
Project Network Analysis PERT
Project Work Scheduling

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 PERT
Example of three time estimate
• For an activity “design foundation”
– the optimistic time = 14 days
– the most likely time = 18 days and
– the pessimistic time estimates = 28 days
• The PERT technique assumes that the three
time estimates of an activity are random
variables and the frequency distribution of
duration of an activity takes the shape of Beta
distribution
60
Beta distribution for the activity ‘design foundation’

Expected Time te
te=19

to=14 tm=18 tp=28

Activity duration (in days)

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• The average or expected time it is given by
• te= (to+4tm+tp)/6
• For the case of ‘design foundation’, te can be
worked out to be 19 days [(14 + 4 x18 +
28)/6].
• The fact that te > tm in this case, is a reflection
of the extreme position of tp and the
asymmetry in the Beta distribution, even
though computationally the weights given to
to and tp is the same.

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• There has been a lot of criticism on the approach of
obtaining three ‘‘valid’’ time estimates to put into
the PERT formulas.
• It is often difficult to arrive at one activity-time
estimate; three subjective definitions of such
estimates do not help the matter (how optimistic
and pessimistic should one be).
• Nevertheless, the three time estimate also provides
the advantages of ascertaining the variability or
uncertainty associated with a particular set of
estimate.
63
• For example, suppose we have two sets of
estimate provided by the different estimator
for the same ‘design foundation’ activity.
• In order of (te, tm,tp), let the first set of
estimate (14, 18, 28) and the other set of
estimates be (17, 18, 25).
• There is large variability in the estimates of
first estimator compared to the second one,
even though the expected or average activity
duration turns out to be 19 in both the cases
(verify!!!).

64
• In order to measure the uncertainty
associated with the estimate of duration of an
activity, the standard deviation (St) and the
variance Vt are determined, which in PERT are
defined as:
• St = (tp-to)/6 and
• Vt = (St)2
• The formula for St indicates that it is one sixth
of the difference between the two extreme
time estimates.
65
• Further, the greater the uncertainty in time
estimates, the greater the value of (tp-to), and
the more spread out will be the distribution
curve.
• A high St represents a high degree of
uncertainty regarding activity times. In other
words there is a greater chance that the
actual time required to complete the activity
will differ significantly from the expected time
te.

66
• For the two sets of estimate used in ‘design
activity’, the St and Vt would be 2.33 days and
5.44 respectively for first set of estimates
while 1.33 days and 1.77 are the
corresponding values of St and Vt for the
second set of estimates.
The expected length or duration of project Te
is calculated by summing up the expected
duration te’s of activities on the critical path.

67
• The critical path is determined following the
forward pass and backward pass explained
earlier.
• The variance associated with the critical path
is the sum of variances associated with the
activities on the critical path.

68
In case, there is more than one critical path in
a project network, then the path with the
largest variance is chosen to determine the VT
and ST. Mathematically,
• Te= ∑te
• VT = ∑Vt and
• ST=SVT

69
• VT and ST represent variability in the expected
project duration. The higher the VT and ST
values, the more likely it is that the time
required to complete the project will differ
from the expected project length Te.
• As was pointed earlier, to, tm, and tp are
assumed to be a random variable following
Beta distribution in the PERT technique.

70
• Now that, te is the weighted sum of to, tm, and
tp, it is also treated as a random variable.
Since, Te is the sum of te’s it indeed is a
random variable.
• The distribution of Te follows normal
distribution according to the Central Limit
Theorem of statistics.

71
• The behavior of normal distribution is well
known and a number of assumptions can be
drawn which could be useful to a planner or a
project manager.
• For example, it is possible to compute the
probability (index) of whether a project (or a
key stage therein) will be completed on or
before their schedule date(s).
• Of course, all this is possible under the
assumption that the activities of the projects
are statistically independent of each other.

72
• Suppose, it is required to compute the probability of
completing the project within a target duration of TD
days.
• Now given the Te of the project it is possible to
calculate the deviation of TD from Te in units of
standard deviation.
• This is calculated from the normal distribution table.
To adopt the table, a ratio called the standardised
deviation or more often the normal deviate, Z, is
derived. Z is defined as the ratio of the difference in
TD and Te to ST. Mathematically, Z= (TD- Te)/ ST,

73
 Z= (TD- Te)/ ST

Here Z is the number of standard deviations by which TD exceeds Te.

Note that TD might be less than Te, in which case Z is negative. Now the
probability measure the originally sought may be obtained by referring to
the following table, extracted from a standard normal table:

Z Probability of meeting Z Probability of meeting

Due Date Due Date
3.0 .999 1.0 .841
2.8 .997 0.8 .788
2.6 .995 0.6 .726
2.4 .992
0.4 .655
2.2 .986
0.2 .579
2.0 .977
0.0 .500
1.8 .964
1.6 .945
1.4 .919
74
1.2 .885
Z= (TD- Te)/ ST

Z Probability of meeting Z Probability of meeting

Due Date Due Date

-0.2 .421
-2.2 .014
-.4 .345
-.6 .274 -2.4 .008
-.8 .212
-2.6 .005
-1.0 .159

-1.2 .115 -2.8 .003

-1.4 .081
-3.0 .001
-1.6 .055

-1.8 .036
-2.0 .023

75
 Example: PERT Diagram
E (5,14, 17)
30 50
13
B (2,5,14) H(1, 4,7)
2 F (2,5,14) 4
6 D (1,2,3) 6

A
A (3,12,21) C (6, 15, 30) 40 G (4, 5, 12) 60
10 20
4
12 16 6

76
 Expected duration, standard deviations and
variances for activities
Duration (days) Expected Standard Variance
Activity Optimisti Most Pessimisti duration deviation St Vt = (St)2
Id c likely c duration (days) te= (t -t )/6
= p o
duration duration tp (to+4tm+tp)/6
to tm

Col 1 Col 2 Col 3 Col 4 Col 5 Col6 Col 7

10-20 3 12 21 12 3 9
20-30 2 5 14 6 2 4
20-40 6 15 30 16 4 16
30-40 1 2 3 2 1/3 1/9
30-50 5 14 17 13 2 4
40-50 2 5 14 6 2 4
40-60 4 5 12 6 4/3 16/9
77
 Computation of early occurrence and late
occurrence times
No Early occurrence time Late occurrence time Slack
de

10 0 12-12=0 0
20 0+12=12 Min of [(21-6)=15 and (28 - 0
16)=12]=12
30 12+6=18 Min of [(34-13)=21 and (28 - 3
2)=26]=21
40 Max of [(12+16)=28 and Min of [(36-6)=30 and (34 - 0
(18+2)=20]=28 6)=28]=28
50 Max of [(18+13)=31 and 36-2=34 0
(28+6)=34]=34
60 Max of [(34+2)=36 and 36 0
(28+6)=34]=36 78
• Now, the problem of computing the
probability of meeting target duration (TD),
such as 42 days shown in the figure is quite
simple. Since the total area under the normal
curve is exactly one, the cross hatched area
under the normal curve is directly the
probability that the actual completion time,
will be equal to, or less than, 42 days.

• In this case Z= (TD- TE)/ ST, = (42-36)/ 5.48 =

1.09 standard deviations.

79
• In other words, the target duration TD is 1.09
standard deviations greater than the expected
time TE=36 days.
• The equivalent probability P(Z=1.09) can be
read off a normal probability distribution. This
corresponds to a probability of 0.862
(86.2%)which implies that there is a 86.2%
chance that the project will get completed
within 42 days.

80
 Meeting a Target Duration TD

1.09 Standard Deviations

P(t  42 days)
 82.6%

36 42

Time - days
81
 Meeting a Target Duration TD

0 Standard Deviations

P(t  36 days)
 50%

36
36
Time - days
82
 Meeting a Target Duration TD

0.55 Standard Deviations

P(t  33 days)
 29.1%

33 36

Time - days
83
• Assuming that time now is zero, one may expect this
project to end at time 36 days (corresponding
probability of achieving this target being 50%,
verify!!! Hint: TD=36, TE=36 ); and the probability
that it will end on or before the target duration of
42, without expediting the project is approximately
86.2%.
• On the other hand, if one were to schedule towards
TD= 33 days; herein TD<TE; i.e. Z=-0.55 (Note the
negative sign); the corresponding probability would
be 0.291, which is really a very bleak situation.

84
• In the above, the phrase ‘without expediting’ is very
important.
• In certain projects schedules always may be met by
some means or another,
• for example,
– by changing the schedule,
– by changing the project requirement,
– by adding further personnel or facilities, etc.
• However, here it is implied that the probability being
computed hereinabove is the one that the original
schedule will be met without having to expedite the
work in some way or another.
85
• The feature in PERT on the computation of
probability of completing the project in a
particular duration is quite useful especially
for negotiating the duration with an owner by
the executing agency.
• For example, while agreeing on a particular
duration, the executing agency would like to
judge his chances on completing the project in
that duration.

86
• For being reasonably sure of a particular duration, he
would like to attain a probability of more than 95%.
• Thus for the same example, suppose the executing
agency is asked to provide the projected duration for
the project, the agency would find out the duration
corresponding to Z(P=0.95)= 1.65, thus the target
duration for this case could be TD= TE + 1.65 x ST= 36
+ 1.65 x 5.48= approximately 45 days. In other
words, the executing agency would be quite
confident of completing the project in 45 days.

87
 LECTURE 3
PRECEDENCE NETWORK ANALYSIS

88
 PRECEDENCE NETWORK
 it is AON diagram with activities on nodes or boxes and
precedence relationship shown as arrow but precedence
network without arrows also is possible!
 numbering of activity also follows rules similar to that followed
in PERT and CPM
 time estimate for the activity could be one time estimate or
three time estimate
 But the three time estimate needs to be converted into single
time before using in the network, by computing the expected time!
89
PRECEDENCE NETWORK LAYOUT

 many variants of the boxes or nodes in a precedence

network possible based on information the user desires

 For illustration, a typical box used for all the preceding
examples
• has been divided into three horizontal parts, top, middle and
bottom
• top & bottom are again divided vertically into three
compartments, left, center and right

 Sample network diagram given in the following slide

90
PRECEDENCE NETWORK
 Common type of relationship used in CPM and PERT
• FS – Finish to Start relationship
 In reality, other relationships are possible, i.e.
• SS – Start to Start
• SF – Start to Finish
• FF – Finish to Finish
 Precedence networks incorporates the mentioned four types of
relationships

91
 FS – Finish to Start relationship
 Task ‘B’ can’t start unless Task ‘A’ is completed
 For (e.g.) consider a project with two tasks
• Task 1 – HCB works
• Task 2 – Plastering
• Plastering can’t start until HCB work is complete (common dependency)
 Case ‘a’:

12 5 17 17 15 32
FS=0 Plastering
HCB work
12 0 17 17 0 32

•There is no lead or lag

• Plaster commences after complete HCB work 92
 FS – Finish to Start relationship (contd.)
 Case ‘b’: 24 15 39
12 5 17
FS=7
HCB work Plastering
12 0 17 24 0 39
• There is a lead of 7 days
• Plaster commences 7 days after HCB work
 Case ‘c’:

12 5 17 15 15 30
FS=-2
HCB work Plastering
12 0 17 15 0 30
•There is a lag of 2 days
• Plaster commences 2 days before completion of HCB work
93
 FS – Finish to Start relationship (pseudo
activity)
 Case ‘b’:
 Lead of 7 days described as a pseudo activity

12 5 17
FS=0 17 7 24
FS=0 24 15 39
HCB work Pseudo activity
Plastering
12 0 17 17 0 24 24 0 39

94
FF – Finish to Finish relationship

 Task ‘B’ can’t finish unless Task ‘A’ finishes

 For (e.g.) consider a project with two tasks
• Task 1 – Add wiring
• Task 2 – Inspect electrical work
• “Inspect electrical work" can't finish until "Add
wiring" finishes
 Lead-Lag factors shown on the arrow

95
FF – Finish to Finish relationship (contd.)

 represented using a pseudo activity

96
SS – Start to Start relationship
 Task ‘B’ can’t start unless Task ‘A’ start

 For (e.g.) consider a project with two tasks

• Task 1 – Pour foundation
• Task 2 – Level concrete
• “Level concrete" can't begin until "Pour
foundation" begins
 Lead-Lag factors shown on the arrow

97
 SF – Start to Finish relationship
 Task ‘B’ can’t finish unless Task ‘A’ start

 SF dependency can be created between the task we want to

schedule just in time (the predecessor) and its related task (the
successor)
 If successor task updated also, it won't affect the scheduled
dates of the predecessor task
 Can be used for just-in-time scheduling up to a milestone or the
project finish date to minimize the risk of a task finishing late if its
dependent tasks slip
 SF not commonly used in precedence networks, but included
here to have a complete discussion. 98
SF – Start to Finish relationship (contd.)
 the two ways of representing the SF activity are as follows:

99
PRECEDENCE NETWORK LAYOUT (contd.)
 top left compartment – earliest start time

 top centre compartment – activity duration

 top right compartment – earliest finish time
 middle left portion – activity description
 middle right – node number
 bottom left compartment – latest start time
 bottom centre compartment – total float
 bottom right compartment – latest finish time

100
PRECEDENCE NETWORK PROCEDURE

For the above sample example the Forward and

Backward passes is computed in similar manner as
CPM & PERT since only FS type relationship is used!
 Critical path(s) is (are) identified next

 This has activities with zero float logically linked between

the start activity and finish activity
 Float is the difference between the late start and early
start

101
 LECTURE 4

BAR CHART
SCHEDULING THE NETWORK
RESOURCE LEVELING

102
 Bar Chart
In the bar chart method, works are first split in to activities.
These activities are then listed in the order of construction
priorities, generally on the left-hand side column, while the
time scale is plotted horizontally on the top and/or bottom of
the chart.
 The bar against each activity represents its schedule of work
 The start of the bar marks the commencement of the activity
and the end of the bar its completion. The length of the bar
on the calendar scale represents the duration of the activity.
 Bar Chart
No Work
description
Residential
Bldg.

1
2
3
4
5
6
7
8
9
10
11
12
13

Months

Working days
` in month
Working days
cumulative
Cont…

105
 Bar Chart
Bar charts are easy to plot, comprehend and communicate, and are most
appropriate for presentation of schedules. However, as planning
technique, the bar chart is not suitable for complex projects due to the
following reasons:
(a) It does not reflect the relationship between various activities which are a
common feature of all complex projects.
(b) It cannot identify and highlight the emerging critical tasks needing special
attention for preventing schedule slippages, time overruns, and other
bottlenecks.
(c) In complex projects, time durations are often educated guesses. Any
change in schedule or time duration would require a redrawing of the
multi-task bar chart schedule.
 thus, it can be said that the bar chart format is most useful
for presentation of schedules, but as a planning technique, it
is not suitable for scheduling complex projects.
 SCHEDULING THE NETWORK
• A scheduling aims at optimizing resources for completion of the project
within stipulated time objectives.
• Resource optimization implies scheduling of resources according to the
given pattern of their employment.
• Optimization is achieved by suitably adjusting the schedule of non-critical
activities using available floats in such a manner that fluctuations from the
desired pattern of resource utilization are minimized.
The scheduling of network plan involves the following steps;
– Outlining scheduling constraints(Time constraint or Resource Constraint)
– Identifying the floats of each activities to order of (ascending order of floats)
sensitivity.
– Preparing the earliest start time(EST) schedule.
– Determining resource scheduling criteria
– Scheduling critical activities at their EST
– Scheduling non critical activities
– Optimizing other resources
– Validating time objective.

107
 RESOURCE LEVELING

• In resource leveling, the constraint is the fixed

project duration.
• That is the project must get completed by a fixed
date.
The attempt of such heuristic is to reduce peak
requirement of resources and to smooth out period
to period assignments.
– Such problems are also referred to as ‘time limited
resource considerations’ problems.
• The assessment of resources is done using resource
loaded or resource aggregation chart.
 Example to illustrate the concept of
resource leveling.

B(3) F (3)
4 2

A
A (2) D (4) 5 G (4) 6
1 2
4
3 4 5
C (4) E (3)
3 5
4
 3 4 7 7 2 9
B F

5 2 9 9 2 11

0 3 3
3 4 7 11 5 16
A
D G
0 0 3 11 0 16
7 4 11

3 3 6 6 5 11
C E
3 0 6 6 0 11
• Let’s assume that there are a total of 7 activities A to G in the
example network.
• The duration of each of the activities are written below the
arrow while the resource requirement of the activities is
shown in the bracket adjacent to the activity name.
• For example, the duration for activity A is 3 days while the
resource required by this activity is 2 units.
• The early start and late start time of events or nodes are also
shown in the network from which the float available in a
particular activity can be calculated thus critical activities can
be identified.
• The critical path of the network is 1-2-4-5-6 and it consists of
activities A, C, E, and G. The critical path is shown by bold
arrows in the network.
 Steps in Resource leveling
• The project network is prepared based on the data provided
for each activity. Event times and activity times are computed
as illustrated earlier thus total float is also computed for each
of the activities.
The list of activities are ranked in order of their EARLIEST START
date (refer Table in the next slide).
The resources required on daily basis for each of the activities
are summed up and shown in the form of a chart called
resource aggregation or resource loading chart.
Fig 3.2 shows resource loading chart based on the earliest
start time of all the activities. The project takes a total of 87
man days to complete and the daily requirement varies from
a minimum of 2 resources on days 1 to 3 to a maximum of 11
resources on days 4, 5, and 6.
 Resource loading table showing daily requirement of workers
based on EARLY START order

EST T Res. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Act. i
m
e

1-2 0 3 2 2 2 2

2-4 3 3 4 4 4 4

2-3 3 4 3 3 3 3 3

2-5 3 4 4 4 4 4 4

4-5 6 5 3 3 3 3 3 3

3-5 7 2 3 3 3

5-6 11 5 4 4 4 4 4 4

Total 2 2 2 11 11 11 10 6 6 3 3 4 4 4 4 4
Resource aggregation or resource loading
chart based on early start.
 Steps in Resource leveling contd..
• Now the activities are ranked in order of their LATEST START
DATE (refer Table below). It may be noted that the latest start
date of an activity is the latest time of the finish event less the
duration.
• Thus latest start times of activities 1-2, 2-4, 2-3, 4-5, 2-5, 3-5,
and 5-6 are on days 0, 3, 5, 6, 7, 9 and 11 respectively in the
ascending order.
• The resource loading chart shown in Fig below is prepared
based on the ascending order of latest start time of each
activity. It can be noticed that the requirement of resources
varies from a minimum of 2 to a maximum of 10 resources.
 Table 3.2 Resource loading table showing daily requirement of workers
based on LATE START order

Act. LST T Res 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

1-2 0 3 2 2 2 2
2-4 3 3 4 4 4 4
2-3 5 4 3 3 3 3 3
4-5 6 5 3 3 3 3 3 3
2-5 7 4 4 4 4 4 4
3-5 9 2 3 3 3
5-6 11 5 4 4 4 4 4 4
Total 2 2 2 4 4 7 6 10 10 10 10 4 4 4 4 4
Resource aggregation or resource loading
chart based on late start.
 Steps in Resource leveling contd..
• The two resource loading charts obtained from steps 2 and 3 are
compared.
• The two charts provide the two extreme arrangements of resource
requirements.
• In the case that PEAKS AND VALLEYS are seen in the utilization pattern for
a resource, the activities are manipulated by visual inspection and an
acceptable resource requirement is found between the two extremes.
• The bottom-line is to ensure continuous deployment of resources and to
avoid large variations in the utilization pattern.
• One such compromise solution is shown in Fig below (also refer Table
below ). This figure has been obtained by delaying activity 2-5 , 2- 3 and 3-
5 by the number of the float days beyond its early start time and leaving
the rest of activities intact as given in Table first table.
• It has resulted in reducing the peak requirement (from 11 to 10) besides
bringing a gradual change in resource requirement.
Resource loading table showing daily requirement of workers
AFTER LEVELING

t Res. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
ACT.

1-2 3 2 2 2 2
2-4 3 4 4 4 4
2-3 4 3 3 3 3 3
4-5 5 3 3 3 3 3 3
2-5 4 4 4 4 4 4
3-5 2 3 3 3
5-6 5 4 4 4 4 4 4
Total 2 2 2 4 4 7 10 10 10 10 6 4 4 4 4 4
 Resource leveled chart
12

10 Act 5-6
Act 3-5
8
Act 2-5
6 Act 4-5
Act 2-3
4
Act 2-4
2 Act 1-2

0
1 3 5 7 9 11 13 15