Using a Tabu-search Algorithm and 4D Models to Improve Construction Project Schedules

Construction project managers are interested in completing their projects on time and within budget. To do that, they often develop project schedules using a set of standardized tools, such as the Program Evaluation and Review Technique (PERT), the Critical Path Method (CPM) and bar charts. Although useful, these tools offer little help regarding the spatial context (i.e., visualization of conflicts among construction activities) as well as determining the optimal schedule with respect to time, cost and resources. The considerations of these two aspects are left to expert opinion, which can sometimes lead to unexpected conflicts during construction and, in turn, result in project delays and added costs. The main steps of the methodology presented here include 1) the determination of optimal schedules using Tabu-search algorithm that accounts for single or multiple objectives (e.g., duration, costs, resources) depending on the project requirements or project management needs, and 2) the integration of project visualization (i.e., 4D models). The visualization of the optimized schedules allows the project team to check the schedule for completeness and to ensure that sequencing and constructability requirements are satisfied. During the visualization process, further refinement of the schedule can be done. The proposed methodology is demonstrated by using it to create the schedule for a one-story steel-frame building. It is shown that the presented methodology results in an improved schedule for the example project over one that may be expected to be generated without this methodology. The best improvements that could be achieve corresponded to a 13% reduction in the project duration, 4% cost reduction, and 49% decrease in resource fluctuation.