A Remote Bridge Health Monitoring System Using Computational Simulation and GPS Sensor Data

The research project was funded by the UK's Engineering and Physical Sciences Research council through its Structural Integrity scheme. The value of the research grant was 380,000 UK pounds.

The overall objective of the project is the creation of a system employing advanced computational tools coupled with GPS sensors able to remotely monitor the health of operational bridges without on-site inspection. The specific aim of this proposal is to undertake the research necessary to set up a basic remote health monitoring system using sensors network placed on an operational bridge and linked to new finite element/optimisation based health assessment software. The research will integrate the work conducted into the use of GPS for deformation monitoring at the University of Nottingham with the deformation analysis work conducted by Cranfield University.

For investigating a more robust and reliable monitoring system, improving positioning precision, particularly in the vertical direction, and overcoming the deficiency in current GPS satellite geometry, ground based pseudo-satellite (pseudolite) observations have been added to the originally proposed system. A GNSS/pseudolite simulator was developed to evaluate the improvement in satellite geometry. The feasibility of using high rate (100 Hz) GPS receivers for structural deformation monitoring also has been investigated.

In creating a finite element/sensor based fault detection system a number of components have to be put in place. First a finite element model has to be constructed accurately replicating the behaviour of the real world structure which requires developing the existing SAFESA method to include the complexities associated with large civil structures. Secondly the structure has to be equipped with a sensor system which can provide appropriate information on the actual behaviour of the structure during its operational life. In the present case a GPS based system will be used together with conventional measurement methods. Finally, a computational system is required able to indicate the presence and location of potentially serious structural faults by comparing the measured structural responses with those predicted by the finite element analysis. This will involve a linked software system employing validated FE models with automatic adjustment methods incorporating neural nets and conventional optimisation methods. Research into diagnostic methods will be done to support this final task and lead to the creation of a remote health monitoring system.

A fully operational structural deformation and deflection monitoring system has been developed during this project and successfully applied in the data collections conducted on the London Millennium Bridge, the Wilford Suspension Footbridge in Nottingham, and the Humber Bridge, using dual/single GPS receivers, triaxial accelerometers, pseudolites and supplemented by data from an automatic weather station. In-house software packages have been developed for various purposes such as assessment of positioning accuracy, speedy integer ambiguity resolution, GPS error mitigation, system simulation and augmentation, data fusion and extraction of structural dynamics. Results reveal millimetric 3D accuracy is possible with this system. The vibration frequencies extracted from field deformation measurements match very well with those predicted values by the FE models for all three bridges. 12 refereed papers have been published and 38 papers have been presented at 19 international conferences. The University of Nottingham successfully organised an international symposium and workshop focused on this topic which 70 people around world attended. During this project, one professor, one senior lecturer, one senior research fellow, two senior experimental officers, two PhD students, and 18 MSc/MEng students were involved. Extensive international cooperation links have been built with academic, industrial and governmental organisations in Australia, Finland, China , and the UK. Several presitigious prizes were won by the project researchers.