Fuzzy analytic hierarchy process-based safety assessment and resilience repair strategy of old district buildings

In the stage of China’s urbanization transitioning to “quality improvement of existing buildings”, the safety governance of old district buildings has become a key challenge for enhancing urban resilience. Traditional assessment methods mostly focus on individual buildings, lacking the connection between overall risk assessment at the district level and the optimal allocation of restoration resources. To solve this issue, this study constructs a safety state assessment system based on the fuzzy analytic hierarchy process (FAHP), covering four major categories and eight indicators including overall structural inclination, structural component damage, material durability, and foundation stability. The safety state is divided into four risk levels: “low risk”, “moderate risk”, “high risk”, and “severe risk”, and a two-layer fuzzy evaluation model is established. Trapezoidal membership functions combined with the “one-vote veto” mechanism for key indicators are introduced to enable refined safety state assessment of individual buildings. On this basis, a safety resilience quantification method that comprehensively considers direct and indirect economic loss is proposed, and an optimal repair strategy model under resource constraints is established in combination with the restoration efficiency index ( RE ). A case study of an old district in Shenzhen containing 330 buildings is conducted for verification. The results show that compared with the random repair strategy, the proposed optimal repair strategy can reduce indirect economic loss by approximately 70.7%, increase the system resilience index to 0.953, and have a reasonable repair period, providing a practical and systematic quantification tool for district-level safety governance and renewal decision-making.