**5. Conclusions**

This research examines various techniques to estimate delay impacts using the IAP technique. A prototype network was introduced as an example to discuss several concerns. The results of delay analysis by each technique were compared with actual impacts. The advantages and limitations of each approach were identified. Recommendations were given for each approach.

Stepwise insertion with logic and constraints is most recommended. When inserting a fragnet (an activity or activities) in IAP to reflect delay events, both constraints and logical relationships between delay events, their logical predecessors, and successors can be used. Constraints based on the actual date of delay events are the simplest and easiest to use. However, constraints should not be used in "single insertion" and "inserting only owneror contractor-caused delay" approach. In addition, in the case of using constraints, it is essential to check if the impact of delay events is larger than the duration of those delay events. In that case, delay events should be logically connected to their logical predecessor and successors without constraints. This study also identified through an example that inserting delay events by logic also can cause wrong analysis results. The findings of this research will aid delay analysts in identifying what kinds of issues arise in IAP methods and how to avoid them.

The problems dealt in this paper were identified by investigating real big projects having almost 5000 activities. However, real network could not be introduced in this paper. A sample network was used for simplification. This paper has limitations in that it cannot show the complexity and dynamics of real projects. AACE [14] and SCL [16] provides recommended protocols for delay analysis. However, there are still a lot of controversy in delay analysis. The area of delay analysis still does not have a standard practice. More issues in analyzing delay should be investigated and standardized in the future.

**Author Contributions:** Conceptualization, K.J.K. and B.H.; Methodology, K.J.K., B.H. and K.K.; Validation, K.J.K. and K.K.; Formal Analysis, B.H. and M.S.P.; Investigation, M.S.P. and E.W.K.; Writing—Original Draft Preparation, K.J.K.; Writing—Review and Editing, B.H. and K.K.; Visualization, M.S.P. and E.W.K.; Supervision, K.J.K. and K.K.; Project Administration, K.J.K. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (No. 2019R1A2C2010794) and the Chung-Ang University Research Scholarship Grants in 2021.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author.

**Acknowledgments:** The authors acknowledge the contribution of all respondents and facilitators who helped in the study.

**Conflicts of Interest:** The authors declare no conflict of interest.
