Research On Multi-objective Optimization Of Green Construction Projects Based On Improved NSGA-Ⅱ Algorith

Green construction is a new direction for the future development of building construction and an important embodiment of the implementation of sustainable development strategy in the construction field,but in the actual promotion and application of the green construction concept,the investigation found that there are problems of uncoordinated project management such as meeting the schedule cannot guarantee safety and meeting the cost cannot guarantee the environment and resource objectives,leading to the obstruction of the implementation of green construction.Therefore,based on the three major objectives of duration,cost and quality in traditional project management,combined with the characteristics of green construction,a multi-objective optimization model is established by introducing three objectives of safety,environment and resources,while the model is solved by using the improved NSGA-II algorithm to achieve multi-objective optimization of green construction projects and provide green construction project management suggestions for decision makers.The main research contents are as follows.(1)Establishing duration optimization model by network plan diagram method;establishing cost optimization model by cost expenditure form;establishing quality optimization model by considering quality influence factors;establishing safety optimization model based on safety input cost combined with system reliability theory;establishing environment optimization model by type of construction influence factors on environment;establishing resource optimization model based on resource saving degree.In summary,based on the mutual influence relationship among the objectives,a multi-objective comprehensive optimization model of schedule-cost-quality-safetyenvironment-resources for green construction projects is proposed.(2)To address the shortage of local search capability of NSGA-Ⅱ algorithm,the local search idea of climbing algorithm is introduced into NSGA-Ⅱ algorithm by combining the characteristics of multi-objectives of green construction project management to realize the improvement of NSGA-Ⅱ algorithm.The performance of the improved NSGA-Ⅱ algorithm is verified by using test functions ZDT1～ZDT3,so as to realize the improved NSGA-Ⅱ algorithm to solve the multi-objective optimization model of green construction projects.(3)Taking the actual project green construction as an example,the multi-objective optimization model based on the actual project is constructed,each objective criterion is determined,and the NSGA-Ⅱ algorithm and the improved NSGA-Ⅱ algorithm are applied to solve the model separately,and the optimization results of the two algorithms are compared and analyzed to verify that the improved NSGA-Ⅱ algorithm is more effective for the multi-objective optimization of green construction projects.Finally,the optimization results are analyzed to provide decision makers with an effective optimization plan for green construction project management.