Transcript CPM Scheduling A Project Management Tool

Chapter 6
Practical Methods to
Reveal CPM Covert
Activities
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T.L. Martin & Associates Inc.
A. Schedule comparison
software
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Schedule comparison software
• The comparison software notes
changes between updates or between
an update and the baseline schedule.
• One such system, which compares
Primavera CPM schedules, is called
“Primaplan Project Investigator.”
• Another system that compares
Primavera schedules is called “Claim
Digger.”
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Schedule comparison software
• These systems note the differences between the two
compared schedules.
– Activities added and deleted,
– revised activity durations,
– start and finish dates,
– calendars, constraints,
– changes in float,
– changes in critical paths,
– resources,
– quantities, and
– changes in relationships.
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B. Physical versus
metaphysical
dependencies
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Physical versus metaphysical
dependencies
• Physical relationships are those which are required
based on the nature of the work.
– A footing must be excavated prior to concrete
placement, formwork must be completed to a
certain extent prior to rebar placement, rebar must
be completed to a joint prior to concrete
• Contractor sequence preference sometimes is just
mere metaphysical dependency.
– Logic between activities becomes that of abstract
and speculative reasoning.
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Physical versus metaphysical
dependencies
• Very good examples of metaphysical
relationships occur within industrial plant
projects, which are more controlled by labor
resources than by physical dependencies.
(With thousands of feet of pipe work to be installed, work
location timing is scheduled primarily by preference not due to
physical dependencies.)
• In this case the critical path goes through
resources and the sequencing of activities,
for the most part, becomes physically
unrestricted.
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Physical versus metaphysical
dependencies
• The productive work can be performed out-ofsequence requiring the next schedule update
to include the revised logic.
• Since the change affected non-physical
activity dependencies, the update should
indicate that the revised logic did not delay
project completion, since the critical path is
driven by resource use which was simply
shifted to a new location.
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Physical versus metaphysical
dependencies
• However, if the contractor does not have sufficient
resources during the period, the project will be critically
delayed.
• The contractor will argue that the directed change
stopped work on the critical path, and thus it is entitled to
a compensable time extension.
• Depending on the wording of the project contract, the
contractor may be correct.
• One of the owner’s defenses is that the contractor has a
duty to mitigate delay and damages by, among other
things, re-sequencing work.
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Physical versus metaphysical
dependencies
• A CPM schedule, if it is to be a viable tool to
determine delay cause and resulting damage,
must include work quantities and key
resources.
• Otherwise, the CPM schedule becomes a
meaningless magic trick, producing wildly
conflicting results depending which side
produces it, to the bewilderment of the
audience.
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C. Standard delay
evaluation techniques
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Standard delay evaluation
techniques
• Delay may result from contractor responsible
issues, subcontractor failure to perform
and/or supplier problems.
• Generally, the contractor is not entitled to time
for its causes of delay and, if critical, may
have to accelerate the work at its own cost to
ensure timely completion.
• These delays are inexcusable and noncompensable.
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Standard delay evaluation
techniques
• Delay can also result from “neutral events” or from
causes outside the control of both the contractor and
the owner.
• Delays associated with extraordinary weather and
“Acts of God” fall under this category.
• Under most contracts, this type of delay entitles the
contractor to an extension of time but no
compensation.
• This type of delay is considered excusable but noncompensable.
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Standard delay evaluation
techniques
• The third group of delays fall under the responsibility
of the owner and is defined by the contract.
• Generally, owner directed changes, differing site
conditions, owner furnished materials and/or
equipment, owner responsible approvals and
designs, are a few of the areas an owner may cause
delay that would result in a compensable time
extension for a contractor.
• The owner responsible delay is considered excusable
and compensable.
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Standard delay evaluation
techniques
• Only excusable delays that fall along the projects
CPM critical path or paths are to be considered with
respect to contract time extensions.
• A CPM schedule is a dynamic tool, as a project
progresses and the schedule is updated, the critical
path or paths shift.
• A delay to a prior update path may use all available
float plus require additional time, thus shifting the
critical path through the delay event.
• Additionally, actual and potential re-sequencing of
work activities mitigating delay events should be
analyzed.
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Standard delay evaluation
techniques
“As-planned vs. As-built”
• The first delay analysis method compares the original
baseline or as planned schedule with the completed
as built schedule.
• Delay events and delay mitigation are determined
supported by contemporaneous project documents
(daily reports, meeting minutes, memos, letters, etc.)
• The credibility of the analysis rests in the accuracy of
the as planned and as built schedules and the extent
to which delay can be tied to project factual events.
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Standard delay evaluation
techniques “But For”
• The second approach is called the “But For” or
collapsing method.
• An as built schedule is developed including all known
delay events, regardless of contractual responsibility.
• Owner causes of delay are removed, leaving
contractor and non-compensable neutral delay
events.
• The difference between the actual completion date
including owner, contractor and neutral delay and the
forecast completion without owner impacts,
represents the period of compensable delay.
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Standard delay evaluation
techniques “But For”
• The next step is to remove owner and neutral delay
events from the as built schedule.
• The difference between the actual completion date
including owner, contractor and neutral delay and the
forecast completion without owner and neutral
impacts represents the period of inexcusable delay.
• The difference between the completion dates
computed based on contractor delay alone and the
original contract completion represents the period the
contractor may be subject to liquidated damages.
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Standard delay evaluation
techniques “Window” analysis
• The third delay determination technique is called a
“Snapshot” or “Window” analysis.
• This approach generally starts with a reasonable as
planned schedule or baseline and at selected points
in time, chronologically includes delay events.
• Once a time impact is identified and founded upon
contemporaneous project documents, the original
baseline schedule is revised incorporating the delay.
This revised schedule is then used as the basis for
adjustment with the next identified delay.
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Standard delay evaluation
techniques “Window” analysis
• This sequential approach is followed consecutively
through the life of the project by identifying a delay
event and then revising the previously adjusted
schedule, until all impacts are incorporated into the
schedule.
• If this approach is chosen, contractor and owner delay
mitigation efforts such as activity re-sequencing,
reduction in critical activity durations and/or deletion
of work tasks, must also be included timely into the
various “Windows.”
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Standard delay evaluation
techniques “Window” analysis
• This approach can be used during performance to
demonstrate delay. A subnet or fragnet is the best way to
demonstrate a delay.
• A subnet or fragnet is a sequence of new activities and/or
network revisions that are proposed to be added to the
existing schedule to illustrate (graphically and
mathematically) the method for incorporating changed
work that may result in project delay.
• Owners should also prepare independent Time Impact
Analyses (“TIA”) using fragnets inserted into the CPM.
– Discuss, negotiate, and timely resolve the question of
impact at the earliest opportunity.
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Standard delay evaluation
techniques “Window” analysis - How
– Determine which activity or activities on the project
schedule were affected by the changed work
and/or by the delay.
– Review and determine the event timing and
duration of all affected activities.
– From the project record keeping systems and key
staff, determine impacted activity status.
– Prepare a fragnet analysis showing the sequence
of activities necessary to perform the work
required, and/or identifying the effects of the delay.
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Standard delay evaluation
techniques “Window” analysis – How
Example 1
• On February 10, two weeks after the project began,
the project was halted due to a strike.
• At the time of the strike, the general contractor was on
schedule and in the process of clearing and grubbing
the job site.
• Accordingly, on February 14, the contractor wrote the
owner and requested a three (3) day time extension.
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Time Extension Analysis Example 1
301
302
Clear & Grub Site
Start
A27 JAN
Finish
10 FEB
Start Excavation for
Building
303
Complete Excavation for
Building
Start
11 FEB
304
As-Planned
Start Building Footings
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obiliz
e
Re m
2/13
No o
n
Ove Strike
r
2/12
Strike
2/11
2/10
No o
n Str
ike
Example #1
301
Clear & Grub Site
Start
A27 JAN
Finish
A12 FEB
303
TIA01
Complete Excavation for
Building
Strike Delay
(3 Day Delay)
Start
A10 FEB
Finish
A12 FEB
MF 12 FEB
302
304
As-Built
Start Excavation for
Building
Start
A13 FEB
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Start Building Footings
Time Extension Analysis Example 2
• Shortly thereafter and during the construction of
the building foundation, a field directive was
issued by the owner at the start of work on
February 19, instructing the contractor to change
the fill requirements.
• On March 31 the contractor wrote the owner and
requested a seven (7) day time extension.
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2/21 R
es
Buildin tart
g Foot
ings
2/19 C
ha
Requir nge Fill
ement
s
Time Extension Analysis Example 2
303
Complete Excav ation for Builidng
302
Start Excav ation for Building
304
308
Start Building Footings
Start Structural Columns & Walls
Start
A13 FEB
Start
A18 FEB
306
Complete Footings
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2/19 C
ha
Requir nge Fill
ement
s
2/21 R
es
Buildin tart
g Foot
ings
Example #2
302
303
Start Excav ation for Building
Complete Excav ation for Builidng
Start
A13 FEB
304A
TIA02
Start Building Footings
Start
A18 FEB
304B
Changed Fill Requirements
Shut Down Fill (2 Day Delay)
Start
A19 FEB
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Finish
A20 FEB
Restart Building Footings
Start
A21 FEB
Time Extension Analysis Example 3
• During the construction of the building structure, a field
directive added four columns and a new structural wall.
The owner at the start of work on February 26, asked the
contractor to determine the impact on completion, if any,
for this work, if starting March 1.
• On February 27 the contractor wrote the owner and
requested a ten (10) day time extension because of this
issue.
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Time Extension Analysis - Example 3
306
Complete Footings
Start
A25 FEB
304B
Restart Building Footing
Start
A21 FEB
Finish
A24 FEB
310
Columns & Walls Grd Floor
Start
Start
A18
FEB
A25 FEB
Finish
1 MAR
Install Deck for 1st Floor
Start
2 MAR
As-Planned
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Time Extension Analysis - Example 3
Wate on NTP Changed
FND Work
Start
A26 FEB
Finish
28 FEB
Construct New FTG's
Install New Columns
& Wall
Start
1 MAR
Start
6 MAR
Finish
5 MAR
Finish
7 MAR
Fab & Deliver New
Steel Columns
Start
1 MAR
Finish
3 MAR
Contractor Claimed 10 Day Delay
26 FEB through 7 MAR
310
Install Deck 1st Floor
Start
8 MAR
304B
Restart Building
Footing
Start
A21 FEB
Finish
A24 FEB
Columns & Walls Grnd Floor
Start
A25 FEB
Finish
1 MAR
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Contractor’s Analysis #3
Example #3
TA03A
Deck was
planned to start
3/2 and due to the
new columns is
delayed through
3/5. Deck can
actually start prior
to completion of
new columns.
TA03B
TA03D
Wate on NTP Changed
FND Work
Construct New FTGs
Install New Columns
Start
A26 FEB
Start
1 MAR
Start
6 MAR
Finish
28 FEB
Finish
5 MAR
Finish
7 MAR
TA03C
Fab & Deliv er New
Steel Columns
Start
1 MAR
Actual Delay
3/2 through
3/5 - 4 days
Finish
3 MAR
Install Deck for 1st Floor
Start
6 MAR
304B
Restart Building Footing
Columns & Walls Grd Floor
Start
A21 FEB
Finish
A24 FEB
Start
A25 FEB
Finish
1 MAR
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Owner’s TIA #3
Standard delay evaluation
techniques
• There are certain requirements of a credible delay analysis.
– The as planned or baseline schedule must be reasonable
and represent an accurate plan to timely build the project.
– Delay issues identified must be founded in the
contemporaneous project record.
– The CPM schedule must be updated through the life of the
project reflecting actual performance.
– The results of the analysis should pass the “common sense”
test.
– The foundation of the alleged delay must be physically real
not developed through imaginary scheduling tricks.
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D. Performance
Monitoring
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The Schedule Update Process
• Review of the final update package:
– Verify accuracy of submitted information.
– Run comparison software
– Review critical path graphic
– Review update narrative
– Review submitted database calculation settings
– Review resource usage
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Performance Monitoring and Steps to
Maintain a Proper CPM
What to Check on Updated Schedule
1. Are all required deliverables submitted?
Compare with General Conditions
2. Is the NTP on the correct day?
Schedule Execution Report or Total Float Report
3. Is the contract duration correct
Schedule Execution Report or Total Float Report
4. Is the contract amount correct
Schedule Resource Report
5. How many activities?
Schedule Execution Report
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Performance Monitoring and Steps to
Maintain a Proper CPM
6.
7.
8.
9.
10.
Does the critical path seem reasonable?
Critical Path Bar Chart or Total Float Report
Does the cost loading look reasonable?
Cumulative Cost Curve
Is there too much float on activities?
Total Float Report
How many constraints? Are they reasonable?
Schedule Execution Report
How many open ends? Are they reasonable?
Schedule Execution Report
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Performance Monitoring and Steps to
Maintain a Proper CPM
11. Is there unusual logic, especially on the critical
path?
Time Scaled Logic Diagram
Detailed Predecessor/Successor Report
12. Cost loading?
Independent Cost Analysis
Resources Loading Report
13. Manpower loading?
Independent Manpower Analysis
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Performance Monitoring and Steps to
Maintain a Proper CPM
14. Are activity durations appropriate
Bar Chart by Area
Resource Loading Report
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Performance Monitoring and Steps to
Maintain a Proper CPM
Within budget and on-time performance are goals.
The simplest means of achieving budget and
performance is for each participant in the project
execute its duties properly, accept responsibility and
to have a good plan for performance of the work,
updated and communicated properly among the
project team.
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Please continue with
Chapter 7
Example Development of a
Critical Path Schedule
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