Investigating the effect of initial scope establishment on the performance of a project through system dynamics modelling Available to Purchase

Traditional construction procurement is generally used for projects with no unusual features and a well‐established scope. In this method, work progresses sequentially because each step is completed before the next step is started. As such, making changes during construction is problematic and expensive. Design and build (D/B) method allows the client to introduce the contractor's design at any stage resulting in the possibility of having different levels of initial scope establishment. Consequently, the project can gain benefit through buildability and the integration of design and construction. The client's main criteria for selecting D/B procurement are to reduce the time and cost of projects through one point responsibility. Factors that are related to time and cost performance include: the completeness of the client's brief (the level of initial scope establishment by the client), changes made to the project by the client, the stage and manner in which the changes are reffected, degree of project difficulty and coordination efforts with the contractor. It is widely recognized that the initial states of those factors at the beginning of a project affect time and cost performance, but the degree of impact has yet to be studied in details. This study focuses on the effects of different levels of the initial scope establishment prior to engaging the D/B contractor. This is investigated using dynamic simulation approach. It is found that the initial scope development should be roughly in the range between 50 and 70%. Experimentation with the model developed also shows that D/B fast‐track construction with fixed design, procurement and construction schedule is most effective in saving time, whereas D/B with traditional method is best for cost saving.