As part of a major project to restore Brazil’s longest suspension bridge, construction company Teixeira Duarte used optical and strain gauge technology, provided by HBM, to ensure the 90-year-old structure would provide safe passage for numerous pedestrians and vehicles crossing each day. Opened in 1926 to link the island of Santa Catarina to mainland Brazil, the Hercílio Luz bridge maintained its original structure despite sea corrosion and ever-increasing vehicle weight - loads much higher than it was originally designed to bear. Safety fears meant Hercílio Luz was completely closed in 1991, but it has since been declared a historical landmark and plans to restore the bridge put in place. Teixeira Duarte was hired for the complete rehabilitation of the bridge, including replacement of bearing supports in the main towers, reinforcement and recovery of foundations, plus application of new decks for vehicles and pedestrians. The most critical part of the project involved the transfer of load from the central span of the bridge to auxiliary structures.

Fiber Bragg Grating technology to monitor strain

To overcome this challenging step, Teixeira Duarte chose HBM’s technology, including sensors and optical interrogators with Fiber Bragg Grating (FBG) technology to monitor strain at critical points in the structure, electrical sensors for reading of various signals including inclination, temperature, wind and sea current. Ricardo Martins, Teixeira Duarte’ project engineer, said: “The more technically complex activity is the load transfer procedure which consists of the tension relief on the eye-bars allowing their sequential replacement. "The execution of this procedure implied the instrumentation of several points of the original and provisional metallic structure, with strain sensors and the application of other electric sensors as inclinometers - and climatic sensors making the total of 312 sensors. "HBM presented the best offer of supply and installation, achieved through the optimised use of combined technologies; optical technology for strain measurements and data transmission to the control center, electrical for other measurements and a timely installation methodology that was required by the physical schedule of the work.” Full details on this stage of Hercílio Luz Bridge project is available on HBM’s website: https://www.hbm.com/index.php?id=7816