Monitoring of structures using the global positioning system

Previous work has described the application of the Global Positioning Syste m (GPS) to the measurement of movements of large structures (such as darns) ; the effectiveness of validated finite-element modelling in the prediction of the behaviour of structures under a wide range of loading conditions is well known. This paper describes the use of the GPS in a specific applicat ion to the validation of a finite-element model of the Humber Bridge, The H umber Bridge has been in successful operation since its completion and open ing in 1981, and the finite-element model was developed for the continued i nservice monitoring of the bridge under increased traffic loads or other si milar changes. Using the GPS, the deflections of the bridge were measured u nder known loading conditions, and compared to those predicted by the model . Extremely close agreement was obtained. Rather less expected was the abil ity of the GPS to determine the resonant frequency of the structure. Carefu l analysis of the outcome of the validation tests shows that remarkably goo d experimental data can be obtained from GPS signals, and that these data c an be processed to give resonant frequencies of the structure. Close agreem ent is again obtained between these measured frequencies, the natural frequ encies measured by more conventional methods and the natural frequencies pr edicted by the finite-element model. It is concluded that the technique can be applied to the monitoring of structures with displacements of much smal ler amplitude than those of a suspension bridge, and hence that the on-line monitoring of major structures might be readily achieved using GPS-based t echniques.