Research On Multi-objective Optimization Of Prefabricated Construction Project Scheduling

Prefabricated building is of high quality and can be built in a labor-saving and cleaner way,which is a trend in the industry.The project scheduling problem of prefabricated building is related to operation efficiency and benefit of theoverall project.Effective scheduling method can improve resource utilization and save project time and cost.In this paper,the multi-objective optimization problem of assembled construction project scheduling was studied.The characteristics of prefabricated construction project scheduling was analyzed.Based on the theory of multi-mode resource-constrained project scheduling and robust scheduling,the multi-objective intelligent optimization algorithm was applied to study the time/robustness tradeoff problem and the time/cost/resource trade-offs optimization problem respectively,so as to provide project managers with basis fordecision.The main research work includes the following aspects:(1)The construction process of prefabricated building and its scheduling characteristics was analyzed,and the theoretical method and algorithms to solve the scheduling optimization problem was introduced.In addition,the characteristics of multi-mode resource-constrained project scheduling problem and the advantages of non-dominant sorting genetic algorithm were analyzed.(2)The scheduling optimization problem of prefabricated buildings was studied from the perspective of time/robustness tradeoff.The importance of making scheduling with short time limit and strong robustness for assembly-type construction projects was analyzed,and a bi-objective multi-mode scheduling model was put forward.Because of thebi-objective trade-off and dual-constraint features of the model,the multi-dimensional real number coding method was proposed,and the fast non-dominant genetic algorithm(NSGA-II)was improved to obtain pareto solution.Simulation analysis of standard example from PSPLIB proves that the improved strategy can improve the performance of the algorithm.What's more,the proposed model and algorithm were implicatedon a real project,in order that research achievement can guide managers to make decisions and invest resources scientifically and reasonably,where result shows that time and robustness trade-offs optimization problem of the prefabricated construction scheduling can be solved well.By analyzing the influence of the two objectives of different resource inputs in the case,it provides a scientific theoretical basis for decision makers to make resource input strategies.(3)The scheduling problem of prefabricated building construction was studied from the view of multi-index trade-offs of construction period,cost and resource balance.The scheduling optimization model under multi-objective tradeoff is constructed and an adjusted NSGA-III based on reference point selection mechanism was designed to solve the model.The simulation results shows that the convergence and distribution of NSGA-III are stronger in the optimization of high-dimensional multi-objective scheduling of assembly-type construction projects.Taking a prefabricated housing construction as a case,further verify the proposed model and algorithm can help managers arrange resources and construction period of project.