A hybrid simulation model for understanding and managing non-value adding activities in large-scale design and construction projects

In a design and construction project, non-value adding activities (NVAAs) can be defined as ineffective efforts that consume time and/or resources but do not add any value to the project (e.g., erroneous construction leading to rework). These activities are considered to be the main contributors to schedule delays and cost overruns.;Variation, especially of activity duration, is one of the major elements increasing the amount of NVAAs. Negative impact of variation on construction performance can be more apparent considering a highly interdependent construction environment such as large-scale construction projects. Therefore, variation and interdependency are the two critical catalysts amplifying NVAAs. Despite the significance of minimizing NVAAs, the traditional construction management approaches such as CPM/PERT are known to be insufficient to address and control NVAAs. Based on this recognition, managing the combined impact of variation and interdependency has been a primary concern in the lean construction community. To help analyze the combined impact of variation and interdependency, several lean construction researchers have developed "project dice game" models. The project dice game is effective to visualize how the combined impact can generate NVAAs; however, it has limited application to real world construction projects because it lacks: (1) correlation, (2) management actions, and (3) flexibility.;To address this issue, this research aims to develop a hybrid simulation model which can analyze real-world construction projects by overcoming these limitations. For this goal, this research first identifies the nature of NVAAs, examines key construction models and tools in construction management area, and addresses their strengths and weaknesses in terms of dealing with NVAAs. In the second part of this research, a hybrid simulation model is developed by combining strengths of the examined models and tools, and then is applied to two repetitive construction processes taken from literature and two real-world construction projects to validate its applicability. Finally, through these case studies, simulation results are analyzed in order to provide construction managers with some guidelines to minimize the negative impact of NVAAs.;The key findings from the application of the model to these case studies include: (1) For a robust project management, both strategic and operational analysis are simultaneously required since a mismatch between strategic and operational analysis is a root cause of errors and changes, consequently leading to schedule delays and cost overruns in large-scale construction projects. (2) Errors and changes are one of the major sources of NVAAs and these have a tendency to be propagated to other related project elements. Thus, for an effective control of NVAAs, a hybrid approach is required which can identify NVAAs at both strategic and operational level. (3) Construction performance is not simply determined by the amount of NVAAs coming from combined impact of variation and interdependency, but determined by interaction between the amount of NVAAs and the effectiveness of managerial actions to minimize the NVAAs.;The hybrid model developed in this research and the key findings gained through its application to real-world construction projects are envisioned to help construction managers to better understand and manage the dynamics of NVAAs, and ultimately minimize the risk of schedule delays and cost overruns in their large-scale construction projects.