Service scheduling optimization for multiple tower cranes considering the interval time of the cross-tasks

Area of Science:

• Construction Management
• Operations Research
• Optimization

Background:

• Construction projects face delays and cost overruns, particularly large-scale ones with multiple tower cranes.
• Tower crane scheduling is critical for progress, cost, equipment health, and safety, especially with overlapping operational areas.

Purpose of the Study:

• To develop a multi-objective optimization model for multiple tower crane service scheduling (MCSSP) in areas with overlaps.
• To maximize the interval time between cross-tasks and minimize the overall project completion time (makespan).

Main Methods:

• A multi-objective optimization model was formulated for the MCSSP.
• The Non-dominated Sorting Genetic Algorithm II (NSGA-II) was employed with specialized chromosome coding and coevolutionary strategies.
• Task allocation within overlapping areas and task prioritization were key components of the solving procedure.

Main Results:

• The model successfully minimized makespan and maximized cross-task interval time, ensuring collision-free crane operation.
• A case study on the Daxing International Airport demonstrated the Pareto front and the non-dominant relationship of solutions.
• The Pareto optimal solution showed superior performance over single-objective algorithms, balancing makespan and interval time.

Conclusions:

• The proposed model and algorithm effectively address the MCSSP, improving safety and operational efficiency.
• Significant improvements in cross-task intervals were achieved with minimal impact on makespan, preventing simultaneous crane entry into overlapping zones.
• This leads to safer, more stable, and efficient construction operations by reducing collisions and equipment wear.