Structural health monitoring of a stress-ribbon footbridge

• Continuous dynamic monitoring of a stress-ribbon footbridge during 3years. • Analysis of the influence of environmental and operational factors on the footbridge modal properties. • Removal of those effects based on PCA; use of Novelty analysis to build a damage indicator. • Demonstration of the efficiency of the described damage detection methodology. • Simulation of realistic damage scenarios based on experimentally validated FE model. This work describes the development and implementation of a structural health monitoring system on a stress-ribbon footbridge. In a first part, it characterises the implemented continuous dynamic monitoring system and the application of automated operational modal analysis to analyse the variation of modal properties estimates along several years. A correlation analysis is then conducted showing that environmental and operational factors (e.g. temperature and pedestrian traffic) induce significant nonlinear effects on the modal frequency estimates, which may mask subtle early damage. Taking into account linear relations between frequency estimates of different modes, the linear Principal Component Analysis (PCA) is applied to remove those effects. Novelty analysis of the residual errors of PCA is used to build a statistical damage indicator for long term structural health monitoring. Finally, the efficiency of the described damage detection methodology is evidenced by simulating some realistic damage scenarios based on an experimentally validated finite element model and observing the clear deviation of the damage indicator. It is demonstrated that such a dynamic monitoring system can serve as an effective tool for long term bridge health monitoring.