Disruptions caused by out-of-sequence work are major causes of productivity losses, cost overruns, schedule overruns, and rework, either directly or indirectly. Projects often appear to be moving smoothly until suddenly near the end consequences of earlier disruptions appear; resulting in a chain reaction of rippled and unplanned impacts. Traditional scheduling and modeling techniques fall short in grasping the full impacts of these disruptions due to their limited ability to capture the highly dynamic nature of multiple feedback processes within the project. The damaged party tends to use the modeling method that overestimates the losses while the undamaged party does the opposite. That is why the associated claims are seldom settled before turning into disputes. This paper proposes an advanced system dynamics (SD) model that can reasonably grasp the rippled impacts of out-of-sequence work and provide informative forensic analysis of the corresponding project overruns. To this end, the authors utilized a multi-step methodology that involved: (1) forming causal loop diagrams encompassing project work flow and rework cycles; (2) developing mathematical formulations to link the different elements in the causal loops; (3) developing a multi-stage calibration algorithm to ensure the model is capable of replicating planned and actual project behaviors, and (4) formulating procedures for performing different what-if scenarios to provide retrospective and prospective analysis. The model was tested on a case study where it has shown its ability to assess the negative impacts of out-of-sequence work simulate its complex dynamics. This is the first research to focus on the dynamics of out-of-sequence work in the construction body of knowledge. The developed model will assist project participants in properly analyzing and forecasting the direct and indirect effects of out-of-sequence work as well as assessing their corresponding mitigation techniques.
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