The traveling salesman puts-on a hard hat – Tower crane scheduling in construction projects

Abstract

Effective use of site equipment is an essential aspect of construction projects. In particular, tower cranes are critical in large scale projects. This research aims to optimize the cranes’ usage in construction projects by efficiently scheduling the sequence of activities that are processed by each crane on the site while addressing several constraints such as crane collisions and tasks precedence constraints. An integer linear program is developed that is based on the Multiple Travelling Salesmen Problem (MTSP). Two sets of valid inequalities have been added to improve the tractability of the model. This model is then tested on a real-world case study of a large construction site with two tower cranes. In addition, heuristic approaches are introduced to increase the tractability of the model and are compared to the integer program in terms of solution quality and computation time by generating a large data-set of problems with different sizes. The heuristics are based on the cluster-first, route-second idea, where an optimization-based clustering method is used to pre-assign activities to cranes. © 2020 Elsevier B.V.