Integrated framework for the sustainable conservation and rehabilitation of Nepal’s historic bridges

Nepal’s historic bridges, including timber, stone masonry, and early suspension typologies, are vital components of both the national mobility network and the cultural heritage landscape. However, progressive material deterioration, environmental exposure, increasing service demands, and the lack of standardized conservation frameworks have increased their vulnerability. This study develops an integrated multi-criteria decision framework that jointly evaluates structural condition and cultural significance to support systematic conservation planning. Seven structural and four cultural indicators were identified and weighted using the analytic hierarchy process (AHP) based on responses from 191 experts. Material degradation (0.193) and structural deformation (0.153) emerged as the most influential structural indicators, while local cultural importance (0.295) and historic age (0.276) dominated the cultural dimension. The weighted indicators are combined into a composite scoring model with defined decision thresholds on a ten-point scale: scores below 2.883 indicate replacement, values between 2.883 and 6.289 require retrofitting, and scores above 6.289 support continued use with minor intervention. The framework links each decision range with heritage-sensitive strengthening strategies, providing a transparent and reproducible methodology for balancing structural safety and cultural preservation. The proposed model offers a scalable reference for sustainable management of historic bridge infrastructure in Nepal and similar heritage contexts.