Multi-Objective Optimization of Tower Crane Layout Planning in Modular Integrated Construction Considering Efficiency, Cost, and Lifting Safety

With the increase of modular integrated construction (MiC) projects, the planning of tower crane layout (TCLP) becomes vitally essential to achieve a balance among multiple goals, such as efficiency, economy, and safety. However, existing TCLP studies are usually formed as single-objective optimization based on total lifting time for conventional construction sites. There should be trade-offs among multiple goals, especially safety. In addition, the heavier components of MiC, requiring cranes with larger lifting capacity, pose a challenge in terms of cost. Therefore, it is necessary to propose a more general and reasonable model to assist managers in making better decisions for TCLP. This study aims to develop a multi-objective optimization model with efficiency, cost, and lifting safety considerations for MiC projects. Firstly, based on literature research and accident statistics, the total transportation time, total cost of tower cranes, and total lifting moment are chosen as the three optimization objectives. Then, the improved three-objective optimization model, considering module positioning time and separate movement features of tower cranes, is proposed. To solve the proposed multi-objective problem, the evolutionary algorithm NSGA-III is used for solutions. The proposed model can provide a series of trade-off solutions for efficiency, cost, and safety, representing different combinations of crane location, supply point location, and orientation. A MiC project in Hong Kong is studied as a case to verify the feasibility and effectiveness of the proposed model. The results show that the proposed model can determine the optimized layout plan with minimum time, cost, and lifting moment by locating the tower crane point, supply point, and supply point orientation. Disregarding the orientation of the supply point would result in an additional 18.2% transportation time, leading to increased costs. Compared to the original layout scheme, the developed model can save up to 41.7% in transportation time and improve safety by 27.4%.