Construction Planning and SchedulingConstruction Management Training Program For Technical Departments by AIT Extension & PRMP, Government Of Punjab
Santi Charoenpornpattana, Ph.D.Assistant Professor & Director
Construction Engineering & Management ProgramKing Mongkut’s University of Technology Thonburi
AIT Conference Center18th August 2009
Planning and Scheduling
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Three basic objectives of construction project management
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Cost
Time Performance
What is “Planning” ?
• General: “the function of selecting organization’s
objectives and establishing the policies,
procedures, and programs necessary for achieving
them.
• Project management context: “establishing an
predetermined course of action within a forecasted
environment”
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Planning & Control / Time & Cost
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SchedulingCost
Planning
Schedule Control
Cost Control
Time Cost
Planning
Control
Planning & Control / Time & Cost Tools
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Bar Chart/CPM
Estimation/Cost
Planning
Bar Chart/CPM/
S-CurveEarned Value
Time Cost
Planning
Control
What is “Scheduling”• “the function of arranging and sequencing the
planned activities in order to achieving the objectives”
• Questions to be answered:
1. What is the total duration of the project?
2. What are the start and finish dates for the activities?
3. Can a project activity be delayed? How long?
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Real life example• It’s now 8.30 am.
• You want to know the earliest time you can finish personal task for the lecture today:▫ Take a bath (5 min)
▫ Dress up (5 min)
▫ Boil water for tea (10 min)
▫ Food reheat (5 min)
▫ Eat breakfast (10 min)
▫ Having tea (5 min)
▫ Walk to lecture room (5 min)
• Can you be on time for the class? If not, what should I do?
• What is the earliest time you could reach the class?
• How much free time do you have before the class?
• Can I have any break after each task?
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Planning Process
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DESCRIP
OFWORK
OBJECTIVES
PROJECTORGANIZATIO
N
“WHO DOES WHAT”WORK
PACKAGEDESCRIPTION
WORKBREAKDOWNSTRUCTURE
WORKSCHEDULE
PROJECTOBJECTIVE
S
SCOPE OF WORK
WORK PLAN
SCHEDULE
MANPOWER
BUDGET
“WHAT”
“WHO”
1 2
34
6
7
5
“HOW MUCH”PROJECT
BASE PLAN
“WHEN”
“HOW”
LOGICALSEQUENCE
AND RESOURCE
REQUIREMENTS
Source: lecture note Dr. Chotchai Charoenngam, CE70.21 Integrated Project Planning and Control School of Engineering and Technology, AIT - 2008
Typical Scheduling techniques
1. Bar Chart
2. Network Diagram
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Categorizing scheduling techniques
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Bar Chart
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Barchart• Henry L. Gantt, World War I -1917
• Classic technique & Well known
Pro:
▫ Easy, Very effective communication tool
▫ Very popular for representation of simpler schedules
▫ Understandable to all level of management
Con:
▫ Can be complex when have >100 activities
▫ Key shortcoming: No dependencies captured
▫ Most effective as reporting format rather than representation
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Bar Chart – construction phase
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dec
jan
feb
mar
ap
ril
may
jun
e
july
Foundation
Structural
Architectural
M & E
Landscape
TIME
ACTIVITIES
Bar Chart – whole development
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Hierarchy of Bar Charts
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Network Diagram
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Network Diagram• Shows not only timing but also interrelations and
dependencies of the activities
• Logical sequence behind the activities are important
• Two main types of network diagram
1. CPM (Critical Path Method)
2. PERT (Program Evaluation Review Technique)Santi Charoenpornpattana, Ph.D. @2009
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A B C
D
EActivity 1 Activity 2 Activity 3
Activity 4 Activity 5
CPM• Standard scheduling technique in construction
industry
• Logical sequence is the key
• Embedded in all commercial scheduling software (MS Project, Primavera Project Planner, etc)
• Very effective for control purpose
• Specified in the contract of almost all medium to large scale projects as a rule especially for the processes of change order and dispute resolution
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Two ways of representing CPM1. Arrow diagramming
2. Precedence diagramming
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1 2 3 4 5 6Mobilizing
Laying outfootings
Excavatingfootings
Formwork &Concrete
Erecting steel
Formwork procurement
Steel procurement
MobilizingLaying out
footingsExcavating
footingsFormwork & concrete
Erecting steel
Steelprocurement
Formworkprocurement
Steps in CPM scheduling
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Identifying activities
Assigning logical interrelationships between activities
Assigning duration for activities
Calculation
1. Identifying activities•Breaking down project’s work into smaller
elements•Work Breakdown Structure (WBS)
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Templates
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Example 1
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WBS of house construction
Example 2
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WBS of large scale building construction
Numbering
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How many level ?•Until the manageable level
•Until there is no important constraints between sub-activities
•For small to medium construction work, 4-5 levels would be appropriate
•For large-scale project, multiple-linked WBS are used. (Master WBS, GC WBS, SC WBS, etc.) Each is done by different party.
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2. Logical interrelationships•Time-sequence relationships among the
various activities▫Mandatory – technical constraint
Foundation before structure Excavation before backfilling
▫Discretionary – management constraint Resource limitation Organization policy/procedure
▫External – external constraint Seasonal condition Law and regulations
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Example
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1 2
4
5 6
3
AB
C
D
EF
A
C
B D
E
F
Arrow diagram
Precedence diagram
dummy arrow
QuizActivity
Excavation
Foundation
Basement
Structure
Wall
Rafter
Flooring
Rough interior
Roof
Finishing
Landscape
Cleaning upSanti Charoenpornpattana, Ph.D. @2009
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Predecessor-
Excavation
Foundation
Foundation, Basement
Structure
Structure , Wall
Structure
Flooring
Rafter
Rough interior, Roof
Basement, Wall
Landscape, Finishing
Answer
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Excav Found
Base
Struc Floor
Wall
Rafter
Landscape
Rough
Roof
Finishing
Clean
Arrow vs Precedence diagramming
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Arrow vs Precedence diagramming
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3. Duration•Amount of time assigned to complete a
particular activity•How to determine?
▫Historical information▫Information from subcontractor▫Handbook
•Duration = Work Quantity
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Crew production rate
4. Calculation
• Forward & Backward calculation• The questions:
1. What is the total duration of the project?2. What are the start and finish dates for
the activities?3. Can a project activity be delayed? How
long?
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Notations
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Duration Total floati j
Early start Early finish
Late start Late finish
Activity description
Activity DescriptionActivity Description
Earlystart
Earlyfinish
Latestart
Latefinish
Duration
Totalfloat
Forward pass
1 2 3 4 5 6 7
A
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3 TF1 2
0 3
LS LF
A
AA
0 3
LS LF
3
TF
BB
3 7
LS LF
4
TF
4 TF37
LF
B
ES EF
ES EF
EF = ES + D
3
LS
Backward pass
1 2 3 4 5 6 7
A
B
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3 TF1 2
0 3
1 3
A
AA
0 3
0 3
3
0
BB
3 7
3 7
4
0
4 TF37
7
B
ES EF
ES EF
LS = LF - D
LF is assigned or obtained
TF = LF – D – ES
3
3
What is “Float”•Float or slack of activity is a measure of
flexibility, or inherent surplus time in the activity’s scheduling
•It indicates how long the activity can be delayed or extended without having effect on completion of the whole (or part) project
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Example analysisActivity Duration Preceding activity
A 2 -
B 2 A
C 4 B
D 1 A
E 2 D
F 2 C,E
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AA0 2
0 2
2
0
BB2 4
2 4
2
0CC
4 8
4 8
4
0
DD2 3
5 6
1
3EE
3 5
6 8
2
3
FF8 10
8 10
2
0
CRITICAL PATH
What the “critical path” can tell?•The path is critical !
•No delay is allowed in the path
•Management must take special care on all activities along the critical path
•Acceleration of the critical activities can shorten total project duration
•Who cause delay !
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QuizActivity Predecessor Duration
Excavation - 2
Foundation Excavation 4
Basement Foundation 4
Structure Foundation, Basement 8
Wall Structure 4
Rafter Structure , Wall 2
Flooring Structure 3
Rough interior Flooring 3
Roof Rafter 2
Finishing Rough interior, Roof 4
Landscape Basement, Wall 8
Cleaning up Landscape, Finishing 2
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Logical relationships• Four logical relationships:
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AAES EF
LS LF
D
BBES EF
LS LF
D
AAES EF
LS LF
D
BBES EF
LS LF
D
AAES EF
LS LF
D
BBES EF
LS LF
D
AAES EF
LS LF
D
BBES EF
LS LF
D
1. Finish-to-Start (FS) 2. Start-to-Start (SS)
3. Finish-to-Finish (FF) 4. Start-to-Finish (SF)
Can start B only when A finished Can start B only when A started
Can finish B only when A finished Can finish B only when A started
Lag•Waiting duration before beginning of the
subsequent action
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AAES EF
LS LF
D
BBES EF
LS LF
D7
AAES EF
LS LF
D
BBES EF
LS LF
D
5
AAES EF
LS LF
D
BBES EF
LS LF
D
2
AAES EF
LS LF
D
BBES EF
LS LF
D
3
Use of SF SS FF and Lag
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Excavation
Concrete
0 1 2 3 4 5 6 7 8
Excav 1Excav 12
Excav 2Excav 24
Conc 1Conc 14
Conc 2Conc 22
Excav Excav 6
ConcConc6
2
2
Excavation takes 6 days Concrete takes 6 days Concrete can be started after
excavation is already started for 2 days Concrete can be finished after
excavation is already finished for 2 days
Calculation of PDM
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AAES EF
LS LF
0
BBES EF
LS LF
3
CCES EF
LS LF
4
DDES EF
LS LF
2
EEES EF
LS LF
2
FFES EF
LS LF
4
GGES EF
LS LF
6
HHES EF
LS LF
6
IIES EF
LS LF
3
JJES EF
LS LF
2
KKES EF
LS LF
0
1
3
2
1
Calculation of PDM
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AA
0
BB3
CC 4
DD2
EE 2
FF4
GG6
HH
6
II3
JJ2
KK0
1
3
2
1
Calculation of PDM
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AA0 0
0 0
0
BB0 3
0 3
3
CC0 4
1 5
4
DD4 6
4 6
2
EE 4 9
7 9
2
FF 4 8
5 9
4
GG6 12
8 14
6
HH 9 15
9 15
6
II12 15
14 17
3
JJ15 17
15 17
2
KK17 17
17 17
0
1
3
2
1
Quiz
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Float
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Float•Measure of flexibility , inherent surplus
time
•Activity’s allowable delay or extended time without causing delay to whole project
•Terminology :
1) Total float
2) Free float
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Definition•Total Float Amount of time that activity can be
delayed without affecting completion of the whole project
•Free Float Amount of time that activity can be
delayed without delaying the early start of following activity
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Total Float•Total Float (TF) = LF-D-ES
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2 53
8E
6 3
4 84
8C
4 0
1 32
6D
5 3
2 42
4B
2 0
2 20
2A
0 0
2 108
10F
8 0
2 4 6 8 10
AB
DC
EF
1 3 5 7 9
Total Float is share by all activities in the path
Free Float
activitycurrent
activityfollowig EF - ES
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• Free Float (FF) =
Free float is not shared
AA0 0
0 0
0
BB0 3
0 3
3
CC0 4
1 5
4
DD4 6
4 6
2
EE 4 9
7 9
2
FF 4 8
5 9
4
GG6 12
8 14
6
HH 9 15
9 15
6
II12 15
14 17
3
JJ15 17
15 17
2
KK17 17
17 17
0
1
3
2
1
Who own float•Tension between owner and
contractorTension contractor
•Signifiant legal implications
•Problem:
▫Owners seek to push contractors on tight schedule Too many late starts risk overall project
duration
▫Contractors seek flexibility Flexibility has value
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Presentation of schedule
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Questions to ask
•Present to whom?
•Which format ?
•Level of detail?
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CPM
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Bar chart
Bar chart
CPM
Example
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2 53
8E
6 3
4 84
8C
4 0
1 32
6D
5 3
2 42
4B
2 0
2 20
2A
0 0
2 108
10F
8 0
2 4 6 8 10
AB
DC
EF
1 3 5 7 9
Draw Relationship
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2 4 6 8 10
A
B
D
C
E
F
1 3 5 7 9
Delay Claim and Schedule Analysis
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What is “delay”?•Time during which some part of the project
has been extended or not performed due to an unanticipated circumstance
•What causes delay?
•Who involves delay?
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Classification of delay
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Excusable and Non-excusable delays•“Excusable delay” is the one that justified
an extension of the project duration
•Examples of excusable delay?
•“Non-excusable delay” ⇒ extension is not permitted
•How can we know whether the delay is excusable or not? ⇒ “ Contract”
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Examples
• In general conditions of contract:“8.3 Delays and Extensions of Time
8.3.1 If the Contractor is delayed at any time in the progress of the
work by an act or neglect of the Owner or Architect, or of an
employee of either, or of a separate contractor employed by the
Owner, or by changes ordered in the work, or by labor disputes, fire,
unusual delay in deliveries, unavoidable casualties or other causes
beyond the Contractor’s control, or by delay authorized by the
Owner pending arbitration, or by any other causes which the Architect
determines may justify delay, then the Contract Time shall be extended
by Change Order for such reasonable time as the Architect may
determine”
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Source: American Institute of Architect Document A201
“Compensable” and “Non-compensable” delays•Excusable delay
1. Compensable
2. Non-compensable
• If compensable, contractor is entitled to additional compensation (normally money)
• In some cases, compensation without extension of time
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Critical & Non-critical delay•Not all delays result in delay to the whole
project completion
•Critical delay is delay occurred in critical activity, hence it delays the whole project completion
•Excusable but non-critical delay does not justify extension of project duration
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Consequences of excusable delays
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Critical Non-critical
Compensable
Non-compensable
Additional payment and
time extension
Additional payment, but
no time extension
Time extension, but no additional
payment
No time extension, and no
additional payment
How to classify?•Excusable vs Non-excusable
•Critical vs Non-critical
•Compensable vs Non-compensable
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“Contract”
“Schedule analysis”
“Evidence”
Scheduling and delay analysis• Schedules play a very important role in
construction delay claims
• Delay can be identified, defined, and explained by schedules
• Delay of an activity may or may not become delay of the whole project
• Without schedule, difficult to recognize delay
• Objective is to prove Critical or Non-critical delay
• Only delay on critical activity is considered
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Conlucsion•Concept of scheduling•Bar chart•CPM
▫Arrow diagram, PDM▫CPM analysis▫Interpretation
•Float•Presentation of Schedule
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