An Optimization Model for Maximizing the Benefits of Fast-tracking Construction Projects

Fast-track construction projects have become more popular in recent years in response to growing industry demand. By allowing a downstream activity to start with incomplete information from upstream activities, fast-tracking allows for shortening the project duration at the expense of an increased likelihood of rework. This leaves practitioners with the challenge of determining the optimal fast-tracking strategy, which meets project schedule requirements and does not cause excessive amounts of rework. This paper presents an optimization based model that serves as a decision support tool in scheduling fast-track construction projects. The model takes into consideration information exchange between upstream and downstream activities. The objective function of the model is to maximize the net benefits from fast-tracking. Rework time and cost are deduced from the literature on rework in construction projects. The model is illustrated on a small scale case study, which was analyzed under various scenarios. The paper concludes with a discussion of the applicability of the model on complex construction projects. INTRODUCTION Traditionally, construction projects were executed under the Design-BidBuild (DBB) method, which consists of starting execution after the full design package is acquired. In DBB projects, the successor activity starts only when its predecessors are fully completed. This method is time consuming and therefore cannot meet the obligation of emerging sharp deadlines. Fast-tracking, a.k.a. overlapping is a replacement to the DBB approach and has become more popular in recent years in response to growing industry demands (Blacud et al. 2009). It consists of starting the downstream activity before the completion of its upstream (predecessor) activities. Therefore, the downstream activity starts based on unfinished information exchanged from the upstream activities. Sharing incomplete upstream information with downstream activities effectively results in overlapping between upstream and downstream activities, thereby reducing the total project execution period. Nonetheless, starting a downstream activity based on unfinished information introduces the risk of rework in the downstream work should there be a change in upstream information. The information exchanged is also associated with a level of 247 Construction Research Congress 2012 © ASCE 2012