4

CHAPTER 2
LITERATURE REVIEW

2.1. General
Effective management practices need to develop and to overcome the
deficiency of conventional tools and techniques of project management towards
handling the problem of reducing the project duration from a normal period. Planning
should be initiated before construction that continues throughout the life of the
project.
Scheduling of construction project concerns with the identification of the
timing of each activity in a project and total project duration of the project.
Techniques for planning and scheduling are required to adopt and to handle
construction projects. For this study, planning and scheduling techniques for Gantt
Chart and Critical Path Method are used. Thus, these methods are outlined in
literature review. Moreover, nature of project, concept of project management, project
life cycle, steps in planning and scheduling, techniques for planning and scheduling
(theories of Gantt Chart Method and Critical Path Method) are also expressed in this
chapter.

2.2. Nature of Project

A project means doing something new, possibly even something risky or
adventurous. A project is usually a one-time activity with a well-defined set of desired
end result. The temporary nature of projects indicates that a project has definite
beginning and end. [00GDO]

2.3. Project Planning

Planning is the process of developing the project plan. Planning involves the
listing of jobs or activities that have to do and to complete the project. The
requirement of men, material, equipment, and estimates of cost and also the duration
of each of the activity are part of the planning. The plan outlines how the project is to
 5

direct and to achieve the assigned goals. Although the process selected is important,
selecting good skilful people is more important. A successful project is achieved by
people working together with clear responsibilities. The process selected affects
financing, selection of team members, and the project cost, quality and schedule.
[14AAD]

2.3.1. Desired Results of Planning

Project planning is the heart of good project management because it provides
the central communication that coordinates the work of all parties. Planning also
establishes the benchmark for the project control system to track the quality, cost and
timing of the work required to successfully complete the project.
Other benefits that can derive from good project planning are as follows:
1. To finish the project on time.
2. To continue flow of work (no delays).
3. To reduce amount of rework (least amount of changes)
4. To minimize confusions and misunderstandings.
5. To increase knowledge of status of project by everyone.
6. To be meaningful and timely reports to management.
7. To run the project instead of project running you.
8. To knowledge of scheduled times of key parts of the project.
9. To knowledge of distribution of costs of the project.
10. To account of people, defined responsibility or authority.
11. To clear understanding of who does what, when, and how much.
12. To integrate of all work to ensure a quality project for the owner. [14AAD]

2.3.2. Project Teams

The first and most obvious requirement in achieving the objective of
construction management is to select competent teams to undertake all the essential
construction actions. Project teams must assemble to accomplish the work necessary
to complete engineering and construction projects. Team members are important to
succeed of the project. The project manager depends on the teams because he or she
typically does not have the expertise to do all the work required to complete the
project. Project teams are made up of all the participants in the project. Team
members report either part-time or full-time to the project manager and are
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responsible for some aspect of the project’s activities. Team work must be well
coordinated with effective interaction to achieve the shared objective of completing
the scope, budget and schedule constraints of the project. [11RW]
2.3.3. Project Scope Definition
When it comes to project planning, defining the project scope is the most
critical step. Project scope defines those items and activities that are required to meet
the needs of the owner. The purpose of project scope definition is to clearly describe
the boundaries of the project, to provide sufficient information to identify the work to
be performed, to allow the design to proceed without significant changes that may
adversely affect the project budget and schedule. Therefore, the defined scope of the
project usually included into the contractual agreements between the client and the
service provider.
Before design is started, scope must adequately define deliverables, that is,
what will be finished. There should be one or more deliveries addressing each project
objective in the project. Project objectives can be used for defining the project scope.
All the information must be known before starting design because it affects the
project budget and schedule. [11RW]

2.3.4. Project Scheduling

A schedule is the conversion of the project plan into an operating timetable. It
serves as the basic for monitoring and controlling project activity and taken together
with the plan and budget, is probably the major tool for the management of projects.
The basic approach of scheduling techniques is to form a network activity and event
relationship that graphically portrays the sequential relations between the tasks in a
project. Tasks that must precede or follow other tasks are then clearly identified, in
time as well as function. Such a network is a powerful tool for planning and
controlling a project. [07SWN]

2.3.5. Purpose of Work Scheduling

Work scheduling serves the following purposes:
1. It simplifies the project plan. The Gantt Chart type work schedule provides
simplified version of the work plan, which can easily be understood by all
concerned which planning, coordination, execution and control of the
project.
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2. It validates the time objectives. A work schedule shows the planned

sequence of activities, date-wise. While putting the work plan on a calendar
basis, it takes into account reduced efficiency of resources to adverse
climatic conditions and other factors. It verifies the deadlines imposed for
completion of the project and achievement of the milestones.
3. It forecasts the input resources and predicts the output. A work schedule
enables the forecasting of resources and also indicates the pattern of
resource consumption. The time schedule of work forms the basis for
predicting the resource requirement as well as the financial state of the
project in terms of investment, expenditure, output and income. [14AAD]

2.3.6. Procedure for Scheduling Network-based Plan

The process on network scheduling is described step by step with the help of
the critical path method network. The scheduling of network plan involves the
following steps:
1. Outlining scheduling constraints.
2. Identifying the floats of each activity and tabulate activities to the order of
sensitivity.
3. Preparing the earliest start time schedule.
4. Determining resource optimization criteria.
5. Scheduling critical activities.
6. Scheduling non-critical activities.
7. Validating time objectives.
8. Optimizing time
9. Optimizing other resources.
10. Scheduling within resources constraints.
11. Preparing the latest start time schedule
12. Preparing knowledge of distribution of costs of the project
13. Scheduling networks of repetitive projects. [14AAD]

2.3.7. Factors Affecting Work Scheduling

The scheduling of a project plan has to take into consideration many variables
like time, resources, and financial constraints. It is difficult to enumerate principles
governing all such factors which may vary from project to project. However, the
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guidelines given in the following can be considered for developing the schedule of a
project work. [90SJD]

2.3.7.1. Time
The availability of time is a crucial limiting factor in a project. More time
normally implies less investment. Time and cost are correlated factors. There are three
aspects of time which have considered during scheduling.
a. Most of the projects carry time constraints in the form of imposed dates. These
dates may include constraints on steps and completion of way that project
duration is not exceeded, such a schedule is called time limited schedule.
b. The schedule must account for holidays, that are weather days and the non-
working periods. Further, effect of the working season on production
efficiency must also be considered while scheduling activities and connecting
resources adjusted suitably. Such a schedule details the work programme for
execution.
c. Scheduling must make use of the reverse of time available in floats of non-
critical activities to reduce fluctuation in resources requirements or conform to
a given predetermined pattern of resources. For minor fluctuations, working
overtime may also be resorted to. The schedule prepared under resource
constraints is termed as resource limited schedule. [90SJD]

2.3.7.2. Man power

Man power is one of the main factors in the successful execution of projects.
No amount of automation or machinery can replace the manpower needed for
completion of a project. It cannot be treated like a commodity and cannot be
dismissed or re-employed at will.
The task efficiency of labour, weather conditions, nature of work and the
supervisors, leadership- all of these affect labour productivity.
The working hours, overtime and other incentives have considered while
deciding the manpower schedule. The management- labour agreements and the
governing labour laws considerably affect labour employment.
A schedule cannot take care of all the variables but these can be reduced by
working out a uniform trade category- wise manpower requirement schedule or by
fixing a pattern depending upon the manpower availability. [90SJD]
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2.3.7.3. Materials
No project can ever be started without materials. Construction materials are
increasingly becoming scarce, and their procurement is a time consuming process.
The schedule aids in forecasting of materials, and their timely supply determines the
economics and progress of work.
One method could be to stock materials well before they are required so as to
ensure timely supply, that the stock inventory costs money. Generally, the inventory
should be zero before the commencement and other the completion of the project. To
go a step forward, the rule should be made applicable to each activity. But for certain
materials, the procurement action can be based on the guiding principle that materials
inventory must be kept to the minimum. In case of materials in short supply, the
schedule may have to be based on availability constraints. [90SJD]

2.3.7.4. Machinery
The availability of machinery is normally, a limiting factor. For example, in an
activity involving excavation, the schedule may specify a requirement of two dozers,
but one may actually be available of allotted. It would entail a recasting of the whole
schedule. The aim of machinery and equipment scheduling should be to find out the
minimum duration schedule in which the employment of equipment and machinery is
systemically and uniformly distributed based on its availability or allotment. [90SJD]

2.3.7.5. Capitals
Capital is the core of all project activities. The project management aims at
economics and the contractor works for earning profits. The proper management of
money results in saving while its improper use proves ruinous. [90SJD]

2.4. Techniques for Planning and Scheduling

The techniques used for project scheduling will vary depending upon the
project’s size, complexity, duration, personnel and owner requirement. Technique of
planning and scheduling plays a vital role in a project. The various techniques used
for any project planning and scheduling are;
1. Gantt Chart or Bar Chart (GC or BC)
2. Critical Path Method (CPM) [06JAF]
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2.4.1. Gantt Chart or Bar Chart (GC or BC)

One of the oldest and still one of the most useful methods of presenting
schedule information is the Gantt Chart, developed around 1979 by Henry L. Gantt, a
pioneer in the field of scientific management. The Gantt Chart schedule is a graphical
schedule relating to items of work to a time schedule.
In the Gantt Chart method, works are first split into 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 bottom of the chart.
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. Gantt Chart shows all calendar months, working days, weekends, holidays
and non-working days.
Gantt Chart is difficult to pinpoint the critical sequence of activities.
Monitoring of work as well as resource optimization becomes difficult with the use of
these charts only. Moreover, Gantt Chart cannot show clearly the interaction between
earliest start and late finish dates of activities and the resulting float of no critical
activities. [06JAF]

2.4.2. Advantages and Disadvantages of Gantt Chart

Gantt Chart is one of the oldest and still one of the most useful methods of
presenting schedule information. There has the advantages and disadvantages. The
advantages of Gantt Chart are as follows:
1. The Gantt Chart is simple to prepare and interpret.
2. Each item of work is shown separately.
3. Modification to the chart can be carried easily.
4. The communication of team members can be improved.
5. It helps project members to understand the severity of time delays.
The disadvantages of Gantt Chart are as follows:
1. It is difficult to prepare the Gantt Chart for large projects if there are
numerous and complex relationships between the tasks that make up the
schedule.
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2. It does not show the interdependency among different activities of the

project.
3. Although it represents the time period over which tasks will be completed,
how much work is required to complete a task is not showed.
4. It does not give any glue about the interrelationship between the activities.
If out of so many activities, one is delayed, how this reflect on other activities
cannot be read from the Gantt Chart. [06JAF]

2.4.3. Critical Path Method (CPM)

A critical path is a sequence of tasks that must be completed on time to enable
project completion on time. A critical path network is a deterministic approach to
scheduling. It was developed in 1956 the DuPont Company. The CPM system shows
the order and interdependence of activities and the sequence in which the work is to
be accomplished.
CPM shows the network of activity and event relationship. A critical path is
normally characterized by zero total float on the critical path. The activities are
represented by arrowed lines and events by circles. The activities are connected in
logical sequence. The time allotted to each activity is related to cost. While adopting
CPM for scheduling the construction project, following steps should be followed.
1. Prepare a list of activities involved in the project.
2. Decide the relationship between listed activities and arrange them in the
order of their occurrence. In the other words, list the activities which
immediately precede and follow other activities.
3. Interconnect the activities in most logical sequence and prepare a network
diagram.
4. Allot time to each activity depending upon the available resources, expected
hurdles and extent of the work evolved in particular job.
5. Number the events in serial order as 1,2,3, … and activities by A,B.C….
capital letters.
6. Mark the critical path in the network and calculate the time required to
complete the project.
7. Determine the earliest start, earliest finish, late start and late finish time for
each activity.
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8. Calculate the float available in the activities not falling on critical path.
Float for activities lying on critical path is zero. [06JAF]

2.4.4. Considerations while Preparing a CPM Network Diagram

The following points must be considered while preparing a CPM network
diagram.
1. An activity is represented by an arrow proceeding from left to right. It
must have two nodes or circles, one at the beginning and one at the end.
Duration of activity is shown at the top of the activity arrowed line and
description below it.
2. Activities can have only two types of relationships. One is in series and
other is in parallel. When activities are dependent upon each other, they
are shown in series. Independent activities are shown in parallel.
3. There can be only one start and one finish of the project. In between there
may be any number of activities. No activity should be tangling. They all
must lead to a final finish node.
4. There must not be any looping i.e.; no activity should lead back to
previous event. A dummy activity only shows inter-dependence and
consumes no time and resource. It is shown dotted line. [06JAF]

2.4.5. Basic Definitions for CPM

Activity – the performance of the task required to complete the project. An
activity requires time and cost.
Network – a diagram to represent the relationship of activities and to complete
the project. The network may be drawn as either an arrow diagram or precedence
diagram as shown in Figure 2.1. and Figure 2.2.
D

B F
A B´ H

C G
E
Figure 2.1. Arrow Diagram [06JAF]
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B D F

A H

C E G
Figure 2.2. Precedence Diagram [06JAF]
Duration (D) – the estimated time required to perform an activity. The time
should include all resources that are assigned to the activity.
Early start (ES) – the earliest time an activity can be started.
Early finish (EF) – the earliest time an activity can be finished and is equal to
the early start plus the duration.
EF = ES + D (2.1)
Late Start (LS) – the latest time an activity can be started without delaying the
completion date of the project.
LS = LF – D (2.2)
Late Finish (LF) – the latest time an activity can be finished.
Total Float (TF) – the amount of time an activity may be delayed without the
delaying the completion date of the project.
TF = LF – EF = LS – ES (2.3)
Free Float (FF) – the amount of time an activity may be delayed without
delaying the early start time of the immediately following activity.
FFi = ESj – Efi (2.4)
where the subscript i represents the preceding activity and the subscript j represents
the following activity.
Critical Path – A series of interconnected through the network diagram, with
each activity having zero free and total float time. The critical path determines the
minimum time to complete the project.
Dummy Activity – an activity represented by a dotted line on the arrow
network diagram that indicated that activity following the dummy cannot be started
until the activity or activities preceding the dummy are completed. The dummy does
not require anytime. [06JAF]

2.4.6. Advantages of CPM

Adoption of CPM technique in construction industry is rapidly increasing
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because of the following advantages.

1. If something goes wrong with the planning of project, it can be easily
identified and then concentration of attention and labour is done to correct.
2. It helps in preparation of the most economical time table for all the
operations of the project.
3. It helps in selection of the best combination of equipment and labour so as
to finish up the project in time.
4. It names the activities which are controlled with respect to their time of
completion for successful finish of the project as a whole.
5. It assists in working out the effect of variations as extra-work, change of
the order of work, etc. up to the time of completion and upon the cost of
the project.
6. It gives sufficient flexibility to the management to suit their requirements
and obligations.
7. It makes the most economical use of available resources.
8. It permits reviewing of the project at various stages and accordingly
allowances may be made to accommodate. Uncertainties which were not
thought in origin planning.
9. It rationalizes construction costing and financing.
10. It shows the activities which can be reasonably delayed without showing
any impact on the final completion period of the project.
11. The study of information and data available from this method suggest
alternative schemes also.
12. The use of this method makes it possible to work out the optimum project
duration. It merely represents a logical mathematical model of the project.
[06JAF]

2.4.7. Steps in Critical Path Scheduling

To apply the critical path method (CPM) of scheduling and the construction of
a project use the following steps:
1. Separate the project into discrete activities, each with a definite starting
point and ending point. Estimate the duration of each activity.
2. Determine the proper sequencing of each activity including which
activities must precede or follow other activities.
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3. Draw network with the activities and events properly interconnected.

Where necessary, include dummy activities to clarify the network and to
avoid redundancy in activity event numbers.
4. Examine the network and optimize, if possible, to eliminate unnecessary
dummy activities.
5. Assign numbers to all events; being sure that the “from” number is always
less than the “to” number. This establishes the proper direction of the
activities.
6. Make a forward pass and a backward pass through the network to establish
early start, late start, early finish and late finish times for all activities.
7. Determine the critical path, or paths and critical activities.
Prepare a table listing all activities, their durations and ES, LS, EF and LF
times and their total float. Their free float can also be listed, if necessary. [06JAF]

2.5. Estimating
Estimation or estimating is the process of finding an estimate, or
approximation, which is a value that is usable for some purpose even if input data
may be incomplete, uncertain, or unstable. The value is nonetheless useable because it
is derived from the best information available. The construction of quantities and the
rates of materials required for a project, calculation of workers and their wages or
salaries is known as estimation in construction.
A cost estimate is the approximation of the cost of a program, project, or
operation. The cost estimate is the product of the cost estimating process. The cost
estimate has a single total value and may have identifiable component values. In spite
of the many types of cost estimates used at different stages of a project, cost estimates
can best be classified into three major categories according to their functions. Of
course, builders and clients both worry about the financial Impact of cost overruns
and failing to complete a project. That’s why they devote time and effort to estimating
how much a project will cost before deciding to move forward with it. Clients
considering large projects often seek multiple cost estimates, including those prepared
by contractors.
A cost estimate establishes the base line of the project cost at different stages
of development of the project. A cost estimate at a given stage of project development
represents a prediction provided by the cost engineer or estimator on the basis of the
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available data. Estimations with constructed facilities are land acquisition, planning
and feasibility studies, architectural and engineering design, construction materials
including equipment and labour, field supervision of construction, construction
financing, insurance and taxes during construction and inspection and testing.
Engineering judgement and experience are utilized in the application of scientific
principles and techniques to the problem of cost estimation and cost control. [98BND]
2.6. Purpose of Estimating
Estimating in construction is important because almost everyone has a budget
they have to meet for a project. Once the customer has the estimate they decide how
much if any work they would like to schedule and the estimate is used as a starting
point for billing later.
1. To ascertain the required
(a) Amount of money
(b) Quantity of material
(c) Number of different categories of workers
(d) Tools, equipment and plants
2. To fixed up the completion period
3. To draw up construction schedule
4. To justify the investment from benefit cost ratio [98BND]

2.7. Types of Estimates

Estimating is the process of finding an estimate, or approximation, which is a
value that is usable for some purpose even if input data may be incomplete, uncertain,
or unstable. The value is nonetheless useable because it is derived from the best
information available. Different types of estimates are as follow:
1. Preliminary Estimate
2. Plinth Area Estimate (PAE)
3. Cubical Content Estimate (CCE)
4. Approximate Quantity Method Estimate
5. Detailed Estimate
6. Revised Estimate
7. Supplementary Estimate
8. Annual Repair or Maintenance Estimate [98BND]
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2.7.1. Preliminary Estimate

It is prepared from the knowledge and cost of the similar works.It is
accompanied by a brief report explaining the necessity and utility of the project and
showing how the cost of separate items have been arrived at.It is also accompanied
with a site plan or layout plan.A percentage of 5% to10% is added as contingencies.
[98BND]

2.7.2. Plinth Area Estimate (P.A.E)

It is prepared on the basis of plinth area of building, the rate being deducted
from the cost of similar building having similar specification, heights and construction
in the locality. The plinth area should be calculated for the covered area by taking
external dimension of the building at the floor level. Courtyard and other open area
should not be included in the plinth area.For storeyed building, the plinth area
estimate is prepared for each storey separately. [98BND]

2.7.3. Cubical Content Estimate (C.C.E)

It is a preliminary estimate or an approximate estimate and is prepared on the
basic of the cubical content of the building and multiplied it by the cube rate (the cost
of similar building having similar specifications and construction in the locality.
[98BND]

2.7.4. Approximate Quantity Method Estimate

In the method, approximate total length of walls is found in running metre and
this total length multiplied by the rate per running metre of wall gives a fairly accurate
rate. For this method, the plan or line plan of the structure should be available.
[98BND]

2.7.5. Detailed Estimate

It is an accurate estimate and consists of working out the quantities of each
item of works and working the cost. [98BND]

2.7.6. Revised Estimate

It is a detailed estimate and is required to be prepared. [98BND]

2.7.7. Supplementary Estimate

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It is a fresh detailed estimate of the additional works in addition to the original

estimate. [98BND]

2.7.8. Annual Repair Estimate

It is a detailed estimate and is prepared to maintain the structure or work in
proper order and safe condition. [98BND]