Measurement and correlation of displacements on the Severn Suspension Bridge using GPS

The use of global navigation satellite systems (GNSS) to monitor the deformations and displacements of structures is well established. Traditionally, research has focussed on the movements of individual locations upon such a structure. In this study, survey-grade global positioning system (GPS) receivers were placed at nine locations upon the bridge and on the tops of the four support towers, and GNSS (GPS, GLONASS) receivers at five key locations on the two suspension cables of the Severn Suspension Bridge. Data were gathered at 10 Hz and 20 Hz, positioned relative to reference GNSS receivers located nearby, over a period of 4 days. This resulted in a dataset allowing the daily movements of the bridge due to applied loading to be measured to millimetre precision. This paper describes the layout of the survey, as well as the movements of the various GNSS antenna locations relative to each other in terms of 3D displacements as well as the frequencies of the movements. A correlation function is developed and applied on the kinematic GPS data, illustrating the synchronised and relative movements of these locations. Correlation between the movements of the bridge’s support towers and suspension cables is illustrated, and conclusions about this development with respect to the potential application of the technique as part of a Structural Health Monitoring (SHM) system are drawn.