PLANNING AND SCHEDULING DONE BY A CIVIL ENGINEERS

BY HAFIZ JUNAID
PLANNING & SCHEDULING
DONE BY A CIVIL ENGINEERS

Planning & Scheduling
Planning:
Process of choosing the method and
order of work
Scheduling:
Process of determining the interrelationship
of associated timings of operations.

Planning & Scheduling
Network Schedules Non - Network
Schedules
(Bar Charts)
CPM PERT Monte Carlo Simultation Techniques
see network schedule and its
classification

Network Scheduling
Network Scheduling is a method of scheduling
activities by joining them in a series of
interconnected links which reflect relationships
of activities as assigned by the planner.

Basic Assumptions for a Network Schedule
1- The project can be broken down into a group
of activities.
2- Each activity can be assigned a duration.
3- The logic relationship between activities are
known and fixed in the network chain.

Techniques for Network Scheduling
1- CPM (Critical Path Method)
 It is the most popular network-scheduling technique
used in construction.
 Developed in the mid fifties by Morgan Walker &
James E. Kelly for managing the construction,
overhaul, and shutdown of large chemical plants.
 Uses only one possible project duration and the
process is called deterministic.

steps
 In applying the CPM, there are several steps that can be summarized
as follows:
 Define the required tasks and put them down in an ordered
(sequenced) list.
 Create a flowchart or other diagram showing each task in relation to
the others.
 Identify the critical and non-critical relationships (paths) among tasks.
 Determine the expected completion or execution time for each task.
 Locate or devise alternatives (backups) for the most critical paths

Techniques for Network Scheduling (- ctd -)
2- PERT (Program Evaluation & Review Techniques)
 Developed in the mid fifties – but not in connection with
CPM – by the U.S. Navy for the research & development
of their Polaris Misile Program.
 Uses probability distributions rather than fixed values
and, hence, termed as stochastic.

Techniques for Network Scheduling (- ctd -)
3- MONTE CARLO SIMULTATION TECHNIQUES
 Not new technique but its practical use in network scheduling is
new, due to the availability of fast, affordable computers.
 It utilizes simultation to predict a project duration by using
random numbers to assign probable durations to activities and
then solving the CPM algorithm for project duration.
 By repeating the process many times, one can produce a
distribution for the probable project duration.

CRITICAL PATH METHOD (NO)
(BASIC STEPS)
 Splitting of the project into work activities
 Determining logic relationships/interrelationships
between activities.
 Construction of Network Diagrams.
 Assigning durations to work activities. (PERT and
CPM use different techniques for this)
 CPM Calculations resulting in start times, finish
times and float calculations of activities.
 Marking of Critical Path
 Construction of Bar Charts / Time phased diagrams

ACTIVITY (NO)
 An element of work performed during the course of a
project. Or
An amount of work that can be identified so that we
know what it involves and can recognize, when it starts
and finishes.
 An activity normally has an expected duration, an
expected cost, and expected resource requirements.
 A list of activities preceeding any given activity is called
PA list.
 A list of activities immediately preceeding any given
activity is called IPA list.

CLASSIFICATION OF ACTIVITIES (NO)
1- PROCUREMENT
It involves all things that must be brought to the job that require
time, such as permanent materials, temporary materials,
workers, money, equipment and utilities.
2- CONSTRUCTION
It includes the activities necessary to assemble and erect the
facility.
3- MANAGEMENT
It includes all items necessary for the project but not specially
identifies in the first or second category.

ACTIVITY DURATIONS (NO)
 Activity duration is forecasted by any of the several means, including:
(1) Check Past Records.
(2) Check Standards and / or cost guides, if available.
(3) Ask the workers, who will do it
(4) make an educated guess
 Any time units may be allotted to activity durations like days, hours,
weeks, months, shifts, etc.
 In CPM, a single duration is forecasted for an activity.
 In PERT (Program Evaluation & Review Techniques), 3 durations are
forecasted for an activity and mean taken by weighted average method.
Then, Project’s Duration or any Event Completion Time is calculated by
probability distribution.

Network Diagrams
 Any schematic display of the logical relationship of
project activities.
 Always drawn from left to right to reflect project
chronology.
 Usually a combination of arrows and nodes.
 A Network for a project is not unique.
 Mainly of two types:
1. Arrow diagram / Activity-on-arrow diagram
2. Node diagram / Precedence diagram /
Activity-on-node diagram

ARROW DIAGRAMS
 Activity is shown by arrow. Relationship between activities shown by
nodes / events.
Activity
Duration
A B C D
3 5 2 7
 Length of arrow has no relation with the duration/size of activity. It is
just a symbol.
 Head of arrow shows start and tail shows end of activity.
 Customarily arrow always starts from left to right.
i j
5
10 15
20
25

EVENT NUMBERING
 Events are numbered in an
Arrow Diagram.
 For any given Activity, the
head event number should
be greater than the tail
event number
 Each Activity should have
a unique i & j pair.
Situation in Figure 2.14 is
not allowed.

MILESTONES
 Events of some special
significance are called
Milestones.

DUMMY ACTIVITIES
 An activity having zero duration and zero cost (and uses zero
resources) is called Dummy Activity.
 Dummy Activity is represented by Dashed Lined Arrow.
 A Dummy Activity may be
---- Logic Dummy ------- To fulfill logic relationship
---- Numbering Dummy – To avoid same i, j pair for
two activities’
---- Start / Finish Dummy – To give single start or
finish activity in the
network.

ARTIFICIAL ACTIVITY
 When a time delay is needed in a
construction sequence, an Artificial Activity is
introduced.
 An Artificial Activity is associated with time
duration but has zero cost.

ACTIVITY CROSSOVER
 Activity crossover is not allowed in Arrow diagrams. However, if
unavoidable, one of the following configurations may be
adopted:

Example 2
ACTIVITY IPA ACTIVITY IPA
A ------ F A, B, C
B ------ G E, F
C ----- H D, G
D A I D, G
E A, B, C

EXAMPLE 1
ACTIVITY IPA
A -----
B A
C A
D B, C
E C
F C

Figure shows a different way of drawing
the arrow diagram, but with the same
logic:
learn the numbers

Node Diagrams
 Activities shown by Nodes, relationship between
activities shown by arrows or links.
 Nodes may be circles, squares, or rectangles.
 These are easier to construct.
 Generally no need of dummies. Instead dummies
used only to give single start or finish.
 Crossing of arrows or links is allowed.
 CPM calculations are similar to arrow diagrams.

In Figure below, C is the activity name and 10 is the
activity duration shown in a square node..

HOW TO CONSTRUCT NODE DIAGRAMS ?
 Construction of Node diagrams is very easy as compared to
arrow diagrams.
 Sequence steps (SS) are assigned to each activity.
 Any activity is given a sequence step higher than its IPA’s. If
activity B follows activity A and A was on SS1, B will be on SS2.
 We start the diagram by placing the sequence steps across the
page and arranging the activities vertically above the proper
step.
 Activities are then connected with straight lines, according to
their IPA’s.

EXAMPLE 1
ACTIVITY IPA SS
A --- 1
B A 2
C A 2
D B, C 3
E C 3
Fn D, E 4

As there are more than one starting and ending activities,
add a start dummy (St) and a finish dummy (Fn)
ACTIVITY IPA SS ACTIVITY IPA SS
St ---- 1 F A, B, C 3
A St 2 G E, F 4
B St 2 H D, G 5
C St 2 I D, G 5
D A 3 Fn H, I 6
E A, B, C 3 ----- ------ -----

PLANNING AND SCHEDULING DONE BY A CIVIL ENGINEERS

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