Intelligent Modeling of the Circular Economy Sustainability Index in Construction Projects Using an Adaptive Neuro-Fuzzy Inference System (ANFIS)

The circular economy, as a contemporary approach to sustainable development, plays a significant role in improving resource efficiency, reducing waste, and enhancing the environmental performance of construction projects. However, the complex relationships among its influencing indicators necessitate the application of intelligent modeling techniques. Accordingly, this study aimed to model and predict the Circular Economy Sustainability Index in construction projects using an Adaptive Neuro-Fuzzy Inference System (ANFIS) integrated with the Fuzzy Analytic Hierarchy Process (FAHP). This applied research adopted a descriptive–analytical methodology with a mixed-methods approach. Data were collected through questionnaires completed by academic and industry experts. After identifying the key indicators, their relative importance was determined using the FAHP method, while the questionnaire-based indicator data were used to construct the ANFIS model for capturing nonlinear relationships and predicting the sustainability index. A total of 80 questionnaires were distributed, of which 68 valid responses were included in the final analysis, and the dataset was randomly divided into 48 training, 10 validation, and 10 testing observations using a 70%/15%/15% split. The findings revealed that resource efficiency (0.247), design for disassembly (0.214), and construction waste management (0.162) were the highest-weighted circular economy criteria. Furthermore, the ANFIS model demonstrated satisfactory predictive accuracy and generalization capability in the testing phase, achieving RMSE = 0.039, MAPE = 4.2%, and R² = 0.89, thereby accurately predicting the sustainability index with a low error rate. The results indicate that the integrated FAHP–ANFIS framework provides an effective tool for evaluating and predicting circular economy sustainability and can support decision-making by managers and policymakers in promoting sustainable development within construction projects.