IMPACT AS PLANNED-DELAY ANALYSIS

Overview

Impact as Planned Delay Analysis is one of the common methods of Construction Schedule Delay Analysis in construction projects. In this method, the baseline construction schedule is compared with the actual progress of works. It helps to determine, the impact of the delay events on the critical path of the baseline construction schedule and on the overall project finish. The procedures to analyze the impact of delay events using this method on a Construction Schedule are as follows.

Baseline Program

The first step is to prepare a construction schedule which will be used as a baseline program after obtaining the necessary approvals from the stakeholders of the project. For instance, we will prepare a sample construction schedule as shown in figure -1 below, as Baseline Program. The Baseline Program will be considered as As-Planned construction schedule.

Critical Path of Baseline Program

The critical path of the baseline program is shown in figure -2 below. The critical path runs through Design, Structure, Internal finishes/MEP, De-snag /Testing & Commissioning, and Project handover.

Identify the Delay Events

The delay events that have occurred or are expected to occur in the future are to be identified. For instance, we identify the delay in IFC drawings (IFC – Issued for Construction). The IFC drawings are required to start the structure works. The activity “Structure” is a critical activity since it is in the critical path of the baseline program. If there is a delay in any of the critical activities the project finish date will be delayed.

Analyze the Impact of Delay Event

We will create a copy of the baseline program and name it “Impacted Program. Then to analyze the impact of the delay event, we will insert “Delay in IFC Drawings” as a delay event in the program. Then predecessor and successor relationships are to be assigned to the inserted activity. We will assign “Design” as the predecessor with the finish to start relationship and “Structure” as the successor with a finish to start a relationship for the delay event. We will reschedule the program with amendments. The impact of the delay event and the critical path of the impacted program will be shown in the figure-3 below.

Evaluation of Results

The delay event “Delay in IFC drawings” delays the start date of the Structure, which is in the critical path of the program. Note that the project handover date is at the end of the month of March with respect to the As-Planned construction schedule. After we insert the delay event in the impacted program and reschedule the program the project handover date moves to the end of month May. The difference between the project handover date with respect to the As Planned and Impacted construction schedules is 2 months. Therefore, the impact of the delay event is 2 months as in figure 4 below.

Conclusion:

Impact as Planned Delay Analysis method is simple and easy to perform. It requires limited records. This method can be useful when evaluating the potential impact of the delay event prior to starting the work. It would be wise to analyze the impact of the proposed changes using Impact As-Planned delay analysis to estimate the project finish date. However, for large and complex projects, the Impact As-Planned delay analysis is less ideal since it ignores actual progress and the actual sequence of works. The Impact As-Planned delay analysis only accounts for excusable delays. Therefore, if there are several known concurrent delays in the project, this method may not be appropriate.