Comparison of GPS Measurements and Finite

G. W. Roberts, A. H. Dodson and V. Ashkenazi, C. J. Brown and R. Karuna

Abstract:	GPS is frequently demonstrated as being a valuable engi-neering surveying and monitoring tool. The use of real time kinematic GPS has many applications, including its use to monitor the deflection of large structures such as bridges. This information can be of vital importance to structural engineers in the evaluation of structural integ-rity, and RTK GPS is a valuable tool for such monitoring This paper details joint trials recently conducted by the University of Nottingham and Brunel University in which kinematic GPS was used to monitor the deflection of the Humber Bridge under a loading of 160.19 tonnes applied by five lorries moving across the bridge. The trial con-79 sisted of placing four dual frequency GPS receivers and a GPS/GLONASS receiver on the bridge deck, a dual fre-quency GPS receiver upon one of the lorries and refer-ence receivers placed on adjacent to the bridge. The data, gathered at 5 Hz, was then processed in an “On the Fly” manner resulting in a precision of the order of a few mil-limetres. The Humber Bridge has been in continuous operation since its completion in 1981, and at 1.4 km had the long-est single span in the world until the completion of the Akashi Kaikyo Bridge in Japan. Significant displacements occur in the main span under loading. A finite element model was developed for the bridge in order to carry out the continued in-service monitoring of the bridge under increased traffic loads or other similar changes. The GPS derived deflections of the bridge caused by the known loading were compared to the deflections pre-dicted by the finite element model. Extremely close agreement was obtained. In addition, the dynamic per-formance of the structure was obtained by the GPS. Close agreement between the measured frequencies of os-cillation and predicted natural frequency from the finite element model was again found. It is concluded that the technique can be applied to the monitoring of structures with displacements of much smaller amplitudes than those of the suspension bridge, and hence that the on-line monitoring of major structures might be readily achieved using GPS based techniques.
Published in:	Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999) September 14 - 17, 1999 Nashville, TN
Pages:	79 - 84
Cite this article:	Roberts, G. W., Dodson, A. H., Ashkenazi, V., Brown, C. J., Karuna, R., "Comparison of GPS Measurements and Finite," Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999), Nashville, TN, September 1999, pp. 79-84.
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