Table 1 Common delay analysis methods
The common delay analysis methods - which are categorized as per their charcteristics - are depicted in Table 1 below.
Table 1 Common delay analysis methods
Highlighting the facts occurred during the course of the projects, Windows Analysis which compute and apportion the delays retrospectively - is the most preferred delay analysis methods [1]. Table 2 below illustrated the requirements of the foregoing delay analysis methods.
Table 2 Requirement of delay analysis methods
Periodical delays or improvements of Windows Analysis are computed via periodic assessment of variance between the completion date of schedule updated and completion date of As-Planned Schedule. However, apportioning the delays require in-depth elaboration of each window. The window period should be chosen as small as possible so that the fluctuations in the critical path are minimized. Otherwise, total delays and improvements computed by considering the variation between the completion date of schedule update and as-built schedule doesn’t match with the result obtained from window elaboration.
If activities falling into concerned window are on CP in the schedule which is updated as of commencement date of the window, delays or improvements are computed by comparing these activities between successive schedules which are updated as of the beginning and the end of the concerning window [1].
Figure 1 Representation of the methodology of the windows analysis
Capabilities of considering the dynamic nature of the CP and actual work progress are the fundamental strength of this method [2]. The procedure of the windows analysis is depicted as follows;
Develop a baseline schedule. Divide the total period of a construction project into digestible periods which is also named windows or snapshot [1], [3]. Windows size can be selected according to schedule updates, milestones or major delay events [1].
Obtain the first schedule update updated as of end date of the first window including owner’s delays, contractor’s delays and delays resulting from acts of God. Update data should include actual start, actual finish (for completed activities), % completion and remaining duration. Please note that schedule update date should be 1 day after the end date of the window.
Detect the activities on Critical Path via first schedule update through 1st schedule update.
Detect and apportion the delays by comparing the activities on the Critical Path (CP) detected in the first schedule update with the baseline schedule for the first window.
Obtain the second schedule update updated as of as of end date of the second window.
Detect the activities on Critical Path via 2nd schedule update.
Detect and apportion the delays by comparing the activities on the Critical Path (CP) in the first schedules window and second schedule update.
Repeat step 2 for the other windows
Outcomes obtained from each window constitute overall project delays.
Delays and improvement are detected and apportioned by analyzing the activities on CP through following sections
• Early and Late Commencement and Finish date of Activities → Non-Excusable Delay
• Duration Change → Non-Excusable Delay
• New Activities in the Schedule Update → Non-Excusable Delay or Excusable Compensable Delay or Excusable Non-compensable Delay
Possible sources concerning delays and improvement are depicted in Table 1 below.
Table 1 Categorisation of Delays and improvement
[1] Society of Construction Law, “Delay and Disruption Protocol,” Hinckley, UK, 2017.
[2] T. Hegazy and K. Zhang, “Daily Windows Delay Analysis,” J. Constr. Eng. Manag., vol. 131, no. 5, pp. 505–512, 2005.
[3] N. Braimah, “Construction Delay Analysis Techniques—A Review of Application Issues and Improvement Needs,” Buildings, vol. 3, no. 3, pp. 506–531, 2013, doi: 10.3390/buildings3030506.
[4] C. K. Kao and J. Bin Yang, “Comparison of windows-based delay analysis methods,” Int. J. Proj. Manag., vol. 27, no. 4, pp. 408–418, 2009, doi: 10.1016/j.ijproman.2008.05.016.