An Interpretable Multisensor Data Fusion Framework for Intelligent Monitoring of Historical Bridges

Abstract

Historical bridges are often subjected to long-term environmental actions and gradual material degradation, while practical constraints on inspection and intervention make reliable condition assessment highly challenging. In this context, intelligent monitoring systems generate large volumes of heterogeneous sensor data, yet transforming such data into interpretable and actionable information for engineering decision-making remains a key problem. This study proposes an interpretable multisensor data fusion framework for intelligent monitoring of historical bridges, integrating temporal prediction and dependency modelling to achieve system-level anomaly assessment under strong environmental influence. Long short–term memory (LSTM) networks are employed to model the temporal evolution of individual sensor signals and to extract prediction residuals that represent deviations from expected behaviour. To capture nonlinear and non-Gaussian dependencies among heterogeneous sensors, a Copula-based dependency model is constructed on the residual space, enabling coordinated anomaly identification across structural and environmental measurements. A hierarchical fusion strategy is adopted to balance local sensor-group interactions and global system-level behaviour. Furthermore, Shapley value analysis is introduced to quantify the contribution of different sensor groups to detected anomalies, enhancing interpretability and supporting engineering judgement. The framework is validated using 34 months of continuous monitoring data from Lugou Bridge, a historical masonry arch bridge. The results demonstrate that system-level fusion effectively reduces scattered single-sensor alarms and highlights temporally concentrated anomalous periods consistent with documented extreme environmental events. The proposed framework is designed as a generalisable and interpretable solution for long-term multisensor monitoring, with the historical bridge serving as a representative case study.