Effectiveness of GPS technology in monitoring of traffic-induced response of highway steel bridge

Despite some disadvantages, regarding the limited accuracy, the Global Positioning System (GPS) is widely used in monitoring of long-span bridges. This paper is concerned with the analysis of the capabilities and limitations of the use of the GPS technology in monitoring of semi-static and dynamic vertical responses of a highway steel cable-stayed bridge excited by traffic loads. The field test was conducted on the Maxau Rhine Bridge, located over the Rhine River near Karlsruhe, Germany. The so-called baseline method with the Post-Processing mode was applied using two units Leica Viva GS15. The basic characteristics of the GPS background noise before and after filtering were examined in the time and frequency domain. The natural frequencies of the bridge were extracted based on the vertical dynamic displacements recorded in the mid-span of the bridge using GPS and accelerometer. It was shown that the GPS receivers were able to measure only two primary modal frequencies of the bridge. The obtained experimental results proved that the GPS system is an efficient tool in measuring the vertical semi-static displacements of the bridge with satisfactory accuracy. Moreover, GPS is capable of tracking the vertical vibrations of long-period bridges to a few millimeters.