System dynamics modeling approach to quantify change orders impact on labor productivity 1: Principles and model development comparative study

In construction projects, change orders are commonly issued by the owner and may cause interruption to the contractor’s work, resulting in loss of labor productivity, delay, and cost overruns, which may lead to claims. Because of the complexity in linking the cause of the productivity loss to the change order, the relationship is not well understood. The contractor must prove with a credible calculation that the productivity loss was a result of the change order issued by the owner to be able to receive compensation. Compared to all available productivity loss quantification methods, the measured mile approach is considered the most acceptable and popular in litigation. This study is a discourse on the understanding, use, and potential application of system dynamics within quantifying change orders' impact on labor productivity. The model boundary, including Endogenous and Exogenous variables, are identified. After determining the parameters used in modeling, the CLD is constructed to understand the system structure better. A system dynamics model is developed using Vensim software, verified, validated, and utilized to quantitatively measure the influence of the change in the project scope on labor productivity. To examine the applicability of the proposed model, it has been implemented to a real highway construction case study, and the impacts of various variables on labor productivity loss have been studied using the data for two completed highway construction projects from FDOT. The study can be applied to construction projects that faced change orders, and as a result of these changes, the contractor’s performance was affected. The proposed model can be used to determine the primary sources that result in labor productivity loss on a specific type of task.