PROJECT SCHEDULING

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PROJECT SCHEDULING
CHAPTER - 7
Example of a 4D Model
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4D MODELING

• The Need
• 2D drawings and network diagrams do not support
  timely decisions
• Design Construction schedules are too abstract
  to visualize and understand
• 4D technologies are being used to analyze
  visualize
• 4D support computer based analysis of schedule

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THE TECHNOLOGY

• 4D models are very time consuming to generate
  manually
• The difficulty and cost of creating such models
  are currently blocking their widespread adoption.

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INTRODUCTION

• The concept of project scheduling addresses the
  issue of time planning and management
• Simple bar charting concepts as well as network
  scheduling concepts will be introduced in this
  chapter

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BAR CHARTS

• The basic modeling concept of the bar chart is
  the representation of a project work item or
  activity as a time scale bar whose length
  represents the planned duration of the activity
• The length of the bar has two different meanings
• The physical length of the bar represents the
  planned duration of the work item
• It also provides a proportionally scaled baseline
  on which to plot at successive intervals of time,
  the correct percentage complete
• The connected diagram of bars is celled as
  bar-net

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Figure 7-1 Bar Chart Model

• Plan Focus
• Work Focus

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Figure 7-2 Bar Chart Project Models

• Bar Chart Schedule (Plan Focus)
• Bar Chart Updating (Control Focus)

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Figure 7-3 Preliminary Bar-Net Schedule for the
Small Gas Staion
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SCHEDULING LOGIC

• To develop a schedule, the logical sequence, or
  schedule logic
• To understand the role played by sequencing in
  developing a schedule, see fig. 7-4(a), fig.
  7-4(b),Fig. 7-5
• Each element is represented by a labeled circle
  (or node)
• For describing adjacency, relational contact is
  necessary
• Nodes of fig. 7-5 can be joined by a series of
  lined. If the idea of contact is expanded to
  indicate the order, a directed line may be used,
  fig. 7-6b or fig. 7-7
• An example of pier pile driving operation is
  shown in fig.7-8(a), 7-8(b), 7-8(c), 7-8(d)
• In order to schedule a project, the sequence of
  activities and their relationship to one another
  must be defined

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Figure 7-4 Simple Schematic Models

• Schematic view of pier
• Exploded view of pier

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Figure 7-5 Model of Pier Components

• Figure 7-6 Logical Modeling Rationales
• Adjacency of contract modeling
• Physical structure order modeling
• Physical construction order modeling

Figure 7-7 Conceptual Model of Pier component
Relationships
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Figure 7-8 Construction Sequence and Activity
Modeling

• Alternate row pile driving
• Sequential roe pile driving
• Field mishap alteration to pile driving sequence
• Bar chart of pile driving operation

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SCHEDULING NETWORKS

• Scheduling networks consist of nodes and links
• Nodes represent events fig. 7-9(a) fig. 7-9(b)
• Directional link which begins on node I and ends
  on node J
• Length of the link implies duration similar to a
  bar in bar chart
• Networks of activities using nodes and
  directional links
• Fig. 7-10(b), introduction of a dummy activity
• Activity on arrow (AOA) or activity notation,
  fig. 7-10(b) sometimes refers to as i-j notation
• Critical path method (CPM) longest path of the
  network
• CPM helps to determine whether the activity
  critically was changes due to duration changes or
  scheduling delays

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TYPICAL CPM ACTIVITY SEQUENCES

• Fig. 7-12 illustrates logical sequences to
  develop CPM schedules
• Dummy activities have zero duration, they are
  shown by broken arrows

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Figure 7-9
Figure 7-10

• Node to represent an event
• Node to represent an activity

• Activity Network in precedence Network
• Activity network in Arrow Network

Figure 7-11 Mistake in logical sequence
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Figure 7-12 Elements of an Arrow Network
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Figure 7-13 Elements of a Precedence Network
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NETWORK SCHEDULE ANALYSIS USING PRECEDENCE
NOTATION

• Objectives of analyzing a project network
• To find the critical activities that establishes
  longest path minimum duration of the project
• To calculate ES times for each activity
• To calculate LS times for each activity
• To calculate the float, or time available for
  delays for each activity
• Two algorithms to identify longest and critical
  path
• Forward pass
• Backward pass
• Float
• To demonstrate, consider the small procedure
  notion network shown in fig. 7-15, 7-16, 7-17,
  7-18 and 7-19
• Forward pass algorithm EFT(I) EST(I)
  DUR(I)
• Backward pass algorithm LST(J) LFT(J)
  DUR(J)
• Total Float, Free Float, Interfering Float and
  Independent Float

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Figure 7-14 a-d Preliminary Network Diagram
Fig, 7-14a Initial Sketch - Arrow Notation
Fig, 7-14b First Draft Arrow Notation
Fig, 7-14d First Draft Precedence Notation
Fig, 7-14c Initial Sketch Precedence Notation
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Figure 7-15 Precedence Notation Scheduling
Network
Figure 7-16 Calculation of EST(J)
Figure 7-17 Calculation of EST/EFT Value
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Figure 7-19 EST/EFT and LST/LFT Values for Small
Precedence Notation Network
Figure 7-18 Calculation of LFT (I)
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Table 7-1 Four Typed of Activity Float
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SUMMARY

• Resources loaded schedule
• If 12 trucks needed and only 9 trucks available,
  there is a resource conflict or constraint
• Construction is a resource-driven industry
• Both time and resource availability are critical