The Savone bridge on the SS 7 “Appia”: real time and topographic monitoring of thermal strain

Abstract

The Savone bridge is located along the SS 7 rural road “Appia” in the southern territory of Francolise town (Caserta county). It overpasses the Savone river and it is about 150 m long. It has been built in the first part of the 50s and now it shows some problems that have been decided to investigate. Specifically, it has been observed that one of the 8 expansion joints located on the bridge was not correctly positioned. In other words, there was a too high and irregular displacement between the 2 faces of the joint. So, it was time to ask if the whole expansion joint had to be redone or the problem could be located elsewhere. In order to understand what could it be happened, it was decided to put the expansion joint under control via two different methods: a classic topographical way and an innovative real time way. With respect to the first way, 2 reference points were placed across the joint. The space between the faces has been read 6 times with different outside temperature values. This work was also useful to the second because it had to calibrated. The real time monitoring consisted of 4 displacement sensors placed at the 4 ends of the bridge deck and 1 temperature sensor. The sensors read the displacements and temperature 6 times per day for a 6 months period. The data were collected in a central unit and it was possible to download them by a simple click on the computer desktop. In fact, an innovative GSM connection between the central unit and a remote one has been provided. This was the true “real time” monitoring as in every connection it was possible to read the sensors and to become aware of the passing of a car or a truck (excessive or low displacement). Finally, lots of data have been collected. They have been first calibrated with the topographical survey and then correlated with the temperature sensor data with a normalization standard. Results showed that 3 over 4 sensor ends had an erratic behavior. So, it was demonstrated the problem was not located only on the expansion joint itself but also on the lower bearing devices of the bridge

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