The use of GPS at a rate of 100 HZ to detect millimetric vertical deflections of small sized concrete bridges

The last four decades were important for the Brazilian highway system. Financial investments were made so it could expand and many structural solutions for bridges and viaducts were developed. In parallel whit this development, there was a significant raise of pathologies in these structures, due to lack of maintenance procedures. Thus, this paper purposes the use of GPS to create a short-term monitoring plan in order to check the structural behavior of a curved highway concrete bridge in current use. And it present the first results of the research with the L1 GPS carrier frequency and recorded data at a rate of 100 Hz, at the monitoring center span of small concrete bridge located on the Jaguari River, in the city of Extreme which borders Minas Gerais and São Paulo states. The challenge lies in the fact that such structures, small and medium-sized concrete bridges, account for the vast majority of art works of Brazilian highways and, as they are rigid structures, small present up to 5 mm vertical deflections. This experiment was carried out through observations sessions with GPS receivers over the bridge at the span instrumented by conventional structural equipment for further confrontation of results between GPS receivers and classic methods of monitoring. The Continuous Wavelet Transform (CWT) was used to analyze the frequency of the response of the bridge from the residues of double difference carrier phase L1.The analysis of the CWT energy spectrum generated from the data collected with GPS receivers indicated a high concentration of energy in the same frequency bands - of the bridge deck response identified by the Finite Element Modeling and the dynamic load test.

Monitoring; Concrete Bridge; GPS; Filtering Signals; Morlet;Wavelet; Continuous Wavelet Transform.