Optimal material logistics planning in congested construction sites

Scarcity of construction site space imposes serious challenges for contractors in planning material supply and site logistics. Existing models of material logistics and site layout planning face critical performance limitations in congested construction sites, due to their inability of modeling and utilizing interior building spaces for long-term material storage. This paper presents the development of a new Congested Construction Logistics Planning (C2LP) system that facilitates the optimal utilization of interior building spaces by considering shifting some of the non-critical activities in order to generate sufficient interior space for material storage areas. Accordingly, the model is designed to optimize two main conflicting objectives; minimizing site logistics costs and minimizing project criticality. Site logistics cost include material ordering, stock-out, carrying, and layout costs. These two objectives are optimized considering four main categories of decision variables: material supply, interior storage plan, exterior layout, and shifting of non-critical activities. The model is designed to incorporate a group of critical constraints, such as exterior layout and activities-materials spatiotemporal constraints. The performance and capabilities of the proposed model are evaluated using an application example of the construction of a multi-storey building in a congested site.