CPM Delay Analysis

CPM Based Analysis

A number of methods of analysing the effect of delay on completion of the works have been developed utilising the CPM schedules that were prepared at the commencement of a project and during the project.

The most commonly used names for these methods are:

As planned impacted (APIP)
As built but for (ABBF)
Windows analysis
Snapshot analysis

As Planned Impacted Program (ASIP)

The impacted as-planned analysis involves the insertion of delay events into a baseline or as-planned schedule to determine the hypothetical impact of such delay events.

This method involves modifying the baseline or as-planned schedule to include new activities and logic to represent delay events. The difference between the project completion date in the impacted as-planned schedule and the original as-planned schedule quantifies the delay.

This methodology is simple and does not require an as-built schedule. However, it is considered a hypothetical model as it does not rely on as-built data.

The As-Built But For (ABBF)

The ABBF analysis is more difficult to perform than the APIP (above) due to difficulties CPM software have in respect of as-built dates as historical events fixed in time, and the need for being able to obtain accurate records of events.

It is therefore necessary to create a logic network that in fact calculates start and finish dates which are identical to historical start and finish dates.

The analytical steps that are necessary for this technique are as follows:

Prepare a comprehensive list of all changes or unanticipated events that occurred during the programme and relate those changes and events to specific points in time.
Prepare an accurate written description of each major change or event.
Establish whether the change or unanticipated event is compensable and/or excusable.
Document the contractual bases.
Obtain hard copies and computerised disks if possible of the baseline programme and any subsequent revisions.
Establish or confirm as-built dates for critical and near critical activities over the life of the works.
Using the as-built dates up-date the last recorded “as planned” project to reflect the complete history through to completion.
Identify differences between planned and actual critical path performance.
Prepare a table which compares “as planned” and “as-built” start and finish dates as well as “as planned” and “as-built” lag durations for the activities.
Determine the extent of the variations in calendar days for various options where an activity either takes longer to complete, is completed earlier, starts later or starts earlier than planned.
Establish the cause or causes for each variance.
Determine the responsibility for change or unanticipated events.
Incorporate that information in the table noted at (IX) above.
Create a discreet activity for each delay and incorporate it into the network logic.
Adjust the duration of the delayed activity so that the combined duration of the imposed delay and the delayed activity equal the as-built duration of the delayed activity.

Simulations can then be performed by setting to zero the duration of the events but for which the project would have been completed earlier in the case of:

Owner caused delays
Contractor caused delays
All delaying events, and Neutral delays.

The principal benefit of this method is that it produces a method by which an as-built programme can be compared against one which would have transpired had none of the events occurred for which time or money is claimed.

The drawbacks to this method are:

The extraction of somewhat arbitrarily established delays from the as-built programme and the manipulation of that process can conceal the effects of a Contractor’s delays however this can be discovered by running several “what if’ scenarios;
The critical path which contains delaying activities will be the primary critical path at completion of the works and this may not represent the critical path during the construction of the works

Windows Analysis

The windows analysis is based not on the whole Contract period but particular windows in time and therefore looks at events which have affected progress within each window of a Contract sequentially.

In terms of the analysis within the window it can be carried out by any method that appears suitable such as the ABBF discussed above.

Within each window the programme update takes into account any delay inefficiencies which are at the Contractor’s risk and any changes to logic or durations since the last update.

It is therefore appropriate to consider that the programme which closes each window represents the as-built programme at that time and also the as-planned programme for the next window.

There are ten basic steps of the Window Analysis method, they being:

Locate the original baseline programme and all as-planned programmes and updates identifying the original Contract completion date and actual completion date.
Determine the window time periods to be analysed.
List the activities on the first as-planned programme which were programmed to start within the first window period.
Using contemporaneous records identify the actual start and finish dates for the activities listed in step 3.
Analyse the dates and determine the delay or advancement of each activity.
Establish the cause or causes for each delay and determine from the project documentation the responsibility for each variance.
Verify that the status of the programme at the end of the first window is the same as the opening status in the next window.
Repeat stages 3 – 7 until all windows have been analysed.
Calculate the delay to the entire project by adding the net delays and advancement for each window.
Summarise the results of calculation and apportion responsibility.

The principal advantage of the window analysis is that because the window represents a limited period in time it will affect a few activities which renders the interpretation of the results of the analysis more convincing than they turn out to be when the analysis is based on hundreds of activities over the whole Contract period.

Snapshot Analysis

This method is a programme analysis technique which is designed to identify and quantify impacts on the schedule through an analysis of the status of the project at the time critical events occurred.

The as-built history of the project including Contract changes and time imp acts is established up to the event and the programme is recalculated. The as-planned or uncompleted portion of the programme is then used to forecast the outstanding work.

The impact of any delay causing event can then be assessed by comparing the newly established completion date to the previous as planned completion date.

The method of analysis is as follows:

At the start of the analysis identify the as-planned network and gather relevant records and documents.
Identify the first event that is –
- excusable and compensable
- excusable but non compensable.
- neither compensable nor excusable.
Identify the dates on which the events in (2) above occurred.
Using progress data update and re-analyse the network and recalculate the critical path.
Using the update network simulate the relevant event by adding in the particular delay activity and the difference between the forecast end-date and the finish date now calculated is the potential delay.

Once all activity delays have been quantified the origin and causes can then be researched and responsibility for each delay apportioned.

Sixteen categories of productivity loss, which essentially cover the same ground as the aforementioned eleven, were also identified and defined by the Mechanical Contractor’s Association of America (MCAA), as follows:

– Stacking of trades ie. Concurrency of workforce labour.

– Poor Morale and attitude

– Reassignment of manpower

– Crew size inefficiency

– Concurrent operations

– Dilution of supervision

– Learning curve

– Errors and omissions

– Beneficial occupancy

– Joint occupancy

– Site access

– Logistics

– Fatigue

– Ripple

– Overtime

– Season and weather change

Quiz.

1. The primary purpose of delay analysis in construction projects is to:

Assign blame for project delays to specific parties.

Identify the root causes and extent of schedule delays.

Justify cost overruns associated with the project.

Reduce communication between project stakeholders.

2. Common methods used in delay analysis include:

Expert opinion only.

Time Impact Analysis (TIA) and Schedule Window Analysis.

Solely relying on the contractor’s daily logs/diaries/correspondence etc

Focusing on the critical path activities only.

3. A well-documented contemporaneous notice:

Should be sent after a significant delay has already occurred.

Is not required for submitting a delay claim.

Provides a stronger foundation for a potential claim.

Focuses solely on the financial impact of the delay.

4. Excusable delays might include:

Poor planning by the contractor.

Unforeseeable weather conditions.

Delays caused by subcontractors not under the contractor’s control (with proper notice).

Material delivery delays due to supplier issues the contractor could have anticipated.

5. The purpose of a delay claim is to:

Penalize other parties involved in the project.

Recover costs incurred due to a compensable delay.

Extend the project completion date automatically.

Demonstrate the contractor’s inefficiency in project execution.

6. Explain the difference between a excusable delay and a non-excusable delay in a construction project.

7. Describe two key elements a contractor should include in a well-documented delay claim.

8. A construction project experiences a delay due to a labor strike impacting several key subcontractors. The strike was unforeseen and lasted for two weeks. The contractor believes this is an excusable delay and intends to submit a claim for additional costs incurred. • What steps should the contractor take to strengthen their delay claim position