3.1 NETWORK Roger D. H. Warburton Determine Activity Dependencies & Critical Path © Kanabar /...
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Transcript of 3.1 NETWORK Roger D. H. Warburton Determine Activity Dependencies & Critical Path © Kanabar /...
3.1 NETWORK
Roger D. H. Warburton
Determine Activity Dependencies & Critical Path
© Kanabar /Warburton, 2009
1
Objectives2
Objectives Understand concepts associated with
Activity Sequencing Critical Path Schedule Development
KNOWLEDGE AREA: TIME MANAGEMENT
A subset of project management that includes the processes required to ensure timely completion of the project. It consist of activity definition, activity sequencing, activity duration estimating, schedule development, and schedule control.
PMBOK® Guide (PMI)
3
WHERE ARE WE?
Monitor and Control
4
WE COMPLETED …
5
Collect Requirements Define Scope Create WBSScope
WBS “DECOMPOSITION”
6
MakeInvitations
1.2
Design1.2.1
Print1.2.2
Mail1.2.3
MakeInvitations
1.2.2
Mail1.2.2.3
Print1.2.2.2 Layout
1.2.1.1Pre-Press
1.2.2
DEVELOPING THE PROJECT PLAN
AddSequence
&Time!
7
THE PROJECT NETWORK
A flow chart that graphically depicts the sequence, interdependencies, and start and finish times of the project
Leads to a plan of activities that is the critical path through the network
8
FROM WORK PACKAGE TO NETWORK
A
B D
C
FinishStart
9
THE NETWORK
10
1.2
Start
MakeInvitations
1.2
Design1.2.1
Print1.2.2
Mail1.2.3
THE “ARROW”
D cannot start until A, B, and C have been completed
A
C
B D
11
CONSTRUCTING A PROJECT NETWORK
Terminology
Activity:
An element of the project that requires time
A
C
B D
12
TERMINOLOGYPath:
A sequence of connected, dependent activities.
Parallel (Concurrent) Activities:
Activities that can occur at the same time. (If desired)
C
A B D13
EVENT
A point in time when an activity is started or completed.
It does not consume time.
Milestones are events14
BURST ACTIVITYAn activity that has more than one activity
immediately following it (more than one dependency arrow flowing from it).
B
D
A C
15
MERGE ACTIVITYAn activity that has more than one activity
immediately following it (more than one dependency arrow flowing from it).
B
D
AC
16
SIMPLE EXAMPLE WITH EVERYTHING
Activity Predecessor Time
A None 5
B A 15
C A 10
D B,C 30
B
DA
C
17
NOTATIONEarliestStart
IDIdentification
EarliestFinish
Slack Description Slack
LatestStart
Duration LatestFinish
18
SIMPLE EXAMPLE: 1) FORWARD PASS (EARLIEST)
A
5C
10
B
15 D
30
ES ID EF
SL Des SL
LS Dur LF
19
SIMPLE EXAMPLE: 1) FORWARD PASS (EARLIEST)
0 A 5
55 C 15
10
5 B 20
15 20 D 50
30
ES ID EF
SL Des Cr
LS Dur LF
20
SIMPLE EXAMPLE: 2) BACKWARD PASS (LATEST)
C
10 10 20
B
5 15 20 D
20 30 50
Delivery Date= 50
0 A 5
0 5 5
ES ID EF
SL Des SL
LS Dur LF
21
SIMPLE EXAMPLE: 3) SLACK = LS - ES
0 A 5
0
0 5 5 5 C 15
5
10 10 20
5 B 20
0
5 15 20 20 D 50
0
20 30 50
= LF - EF
C can be delayed
by 5
Float
22
SIMPLE EXAMPLE: 4) PATH OF LEAST SLACK (LS – ES)
0 A 5
-10
-10 5 -5 5 C 15
-5
0 10 10
5 B 20
-10
-5 15 10 20 D 50
-10
10 30 40
-5-(+5)= -10 10-(+20)= -1023
SIMPLE EXAMPLE: 5) CRITICAL PATH
0 A 5
0
0 5 5 5 C 15
5
10 10 20
5 B 20
0
5 15 20 20 D 50
0
20 30 50
24
CRITICAL PATH
The critical path is the network path(s) that has (have) the least slack in common.
25
CRITICAL PATH the longest path through the network that allows for the
completion of all activities
the shortest expected time in which the entire project can be completed. Delays on the critical path will delay completion of the entire project.
C
A B D
T=3
T=5
26
CRITICAL PATH ~ 10% Assign best people to critical activities
Prioritize (and eliminate) critical activities
Risk assessment on critical activities
Visit people working on critical activities
Can I borrow Joe?
Overtime, technology
Schedule changes ±
Roll up non criticals C
A B D
T=3
T=5 27
SIMPLE EXAMPLE: 6) FREE SLACK
0 A 5
0
0 5 5
5 C1 10
5
10 5 15
5 B 20
0
5 15 2020 D 50
0
20 30 5010 C2 15
5
15 5 20
Difference between EF and ES that follows it
05
Useful!
EF – ES
28
BASIC NETWORK RULESNetworks typically flow from left to right.An activity cannot begin until all of its
predecessor activities are complete.Arrows indicate precedence and flow and can
cross over each other.Identify each activity with a unique number;
this number must be greater than its predecessors.
Looping is not allowed.Conditional statements are not allowed.Use common start and stop nodes.
29
NETWORK COMPUTATION PROCESS
Forward Pass—Earliest Times
How soon can the activity start?Earliest start—ES
How soon can the activity finish?Earliest finish—EF
How soon can the project finish?Expected time—ET
30
NETWORK COMPUTATION PROCESS
Backward Pass—Latest Times
How late can the activity start?Latest start—LS
How late can the activity finish?Latest finish—LF
Which activities represent the critical path?
How long can it be delayed?Slack or float—SL 31
FORWARD PASS COMPUTATION
Add activity times along each path in the network (ES + Duration = EF).
Carry the early finish (EF) to the next activity where it becomes its early start (ES) unless…
The next succeeding activity is a merge activity, in which case the largest EF of all preceding activities is selected.
32
BACKWARD PASS COMPUTATION
Subtract activity times along each path in the network (LF - Duration = LS).
Carry the late start (LS) to the next activity where it becomes its late finish (LF) unless
The next succeeding activity is a burst activity, in which case the smallest LF of all preceding activities is selected.
33
DETERMINING SLACK (OR FLOAT)
Slack (or Float) The amount of time an activity can be delayed after
the start of a longer parallel activity or activities. Total slack
The amount of time an activity can be delayed without delaying the entire project.
34
ILLOGICAL LOOP
A
C
B
35
ITERATION LOOP
Write CH 1
Edit CH 1??
36
ARROWS MAY CROSS
A
C
B
D37
PRACTICAL CONSIDERATIONS
Network Logic ErrorsActivity NumberingUse of Computers to Develop
NetworksCalendar DatesMultiple Starts and Multiple
Projects38
EXAMPLE OF LADDERING
Dig Hole
Lay Pipe
Fill Hole
Dig 1/3 Hole Lay 1/3 Pipe Fill 1/3 Hole
Dig 2nd/3 Hole
Lay 2nd/3 Pipe
Dig 3rd/3 Hole 39
EXTENDED NETWORK TECHNIQUES:
1) LADDERING100% Complete too restrictiveOverlap & long durationActivities are broken into
segments so the following activity can begin sooner and not delay the work
40
EXTENDED NETWORK TECHNIQUES:
2) LAGS
The minimum amount of time a dependent activity must be delayed to begin or end. Lengthy activities are broken
down to reduce the delay in the start of successor activities.
41
USE OF LAGS
Finish-to-Start Lag
Typical: e.g., Ordering Materials
• Order Activity is 1 day• Material takes 5 days to arrive• Charge for 1 day
Order Assemble5 Days
42
USE OF LAGSStart-to-Start Relationship
Assemble cannot begin until 5 days after Order begins
You can begin Assembly after a portion of Ordering
e.g., pipe laying, partial design
Order
Assemble5 Days
43
USE OF LAGS
Finish-to-Finish Relationship
The finish of Assemble depends on the finish of the Order.
Assemble cannot finish any earlier than 5 days after Ordering is complete
Order
Assemble
5 Days
44
USE OF LAGS
Start-to-Finish Relationship
Assemble cannot end until 5 days after Ordering has started.
(Because information to Assemble is available after the first 5 days of Ordering.)
Order
Assemble
5 Days
45
USE OF LAGS
Can be used in Combinations!
Assemble cannot begin until 5 days after Ordering has started
andOrdering must be finished 3 days before Assemble can be finished.
46
3) HAMMOCK ACTIVITIES
An activity that spans over a segment of a project.
Duration is determined after the network plan is drawn
Used to aggregate sections of the project
Facilitates getting the right amount of detail for specific sections of a project.
47
HAMMOCK ACTIVITY EXAMPLE
Consulting, Machine Rental, etc.
Dig
Hole
Lay
Pipe
Patch
Pipe
Fill
Hole
RentBackhoe
48
CONSTRUCTING A PROJECT NETWORK
Two ApproachesActivity-on-Node (AON)
Uses a node to depict an activity.
Activity-on-Arrow (AOA)Uses an arrow to depict an activity. 49
AOA EXAMPLE
Activity Predecessor Time
A None 5
B A 15
C A 10
D B,C 30
B
DA
C3
41 2A C D 5
B
A is 1-2C is 2-4D is 4-5
B is 3-450
AOA EXAMPLE
Activity Predecessor Time
A None 5
B A 15
C A 10
D B,C 30
B
DA
C3
41 2A C D 5
B
A is 1-2C is 2-4D is 4-5
DummyActivity
B is 3-42-3 is dummy, zero time
51
AOA
Know advantages & Disadvantages
Not expect you to do AOA network
52
AON & AOAAON AOA
+ No Dummy Activities + Paths simplified
+ Easier to draw for simple networks
+ Easier to draw for complex networks
+ Easily understood by managers
+ Key events easily flagged
− Hard to understand for complex networks
− Dummy activities− Emphasizes events, not activities
53
SUMMARY TIME MANAGEMENT (PMBOK 4TH EDITION - 2008)
54
Define Activities Sequence Activities
Estimate Activity Resources
Estimate Activity Durations
Develop Schedule
Time
The following are the Time Management Planning Processes
WORKSHOP
Estimate duration for activities Network and Schedule: Generate a MS
Project Schedule for the case study
ADDITIONAL READING
Good overview of Slack is at: http://office.microsoft.com/en-us/project/HA102118001033.aspx
56