2. Planning & Scheduling
Planning:
Process of choosing the method and
order of work
Scheduling:
Process of determining the interrelationship
of associated timings of operations.
3. Planning & Scheduling
Network Schedules Non - Network
Schedules
(Bar Charts)
CPM PERT Monte Carlo Simultation Techniques
see network schedule and its
classification
4. 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.
5. 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.
6. 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.
7. 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
8. 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.
9. 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.
10. 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
11. 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.
12. 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.
13. 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.
14. 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
15. 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
16. 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.
18. 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.
19.
20.
21. 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.
22. ACTIVITY CROSSOVER
Activity crossover is not allowed in Arrow diagrams. However, if
unavoidable, one of the following configurations may be
adopted:
23. 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
31. 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
32.
33.
34.
35.
36.
37.
38.
39.
40.
41. Figure shows a different way of drawing
the arrow diagram, but with the same
logic:
learn the numbers
42. 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.
43. In Figure below, C is the activity name and 10 is the
activity duration shown in a square node..
46. 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.
49. 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
50. 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 ----- ------ -----