Spatio-temporal planning for tower cranes in construction projects with simulated annealing

Tower crane planning plays an important role in the progress and cost of construction projects. Finding the optimal tower crane planning scheme from a large number of potential candidates is typically regarded as a complex combinatorial optimization problem. To tackle this issue, researchers have attempted to develop mathematical models combined with various optimization algorithms. However, a major limitation is that most previous studies only focused on a specific stage of a construction project rather than all stages or used two-dimensional project data (i.e., quantity and place) without time dimension, neglecting the dynamic nature and changes that occur during the different construction stages. Another problem is that the service period of tower cranes as well as the height ranking among them, which are highly important when multiple tower cranes are used, were rarely taken into account. To address those challenges, this study proposes a spatio-temporal planning model for tower cranes in construction projects with simulated annealing. The interacting planning objects, consisting of number, type, location, service period, and height ranking, are incorporated into a mathematical model, and it pays particular attention to estimating delays caused by waiting for new lifting tasks and avoiding collisions among tower cranes. The capabilities of the proposed planning model are demonstrated through an example of a high-rise building project by testing all feasible initial solutions. The results show that the calculated optimal solutions can provide the savings ranging from 23.27% to 41.73% depending on the different cases, with an average saving of 31.10% of the total cost when compared to the initial solutions.