The 18th century church of Santa Maria del Suffragio in Italy was destroyed by an earthquake in 2009. In order to continuously monitor and control the behaviour of the structure, optical measurement technology from HBK FiberSensing supports the monitoring of strain and temperature in the prestressed tie rods used for reinforcement.
Seven years have passed since then. Santa Maria del Suffragio was one of the first landmark buildings to be partially restored. The use of provisional supports allowed its partial opening to the public one year after the tragedy. Full reconstruction of the church started in 2013 and is still ongoing. The earthquake did not only cause the collapse of the dome but also resulted in structural deficiencies in the whole building.
The structure is not only being reconstructed, but also seismically reinforced to guarantee the stability and safety of this important landmark in the years to come. In order to continuously monitor and control the structure’s behavior, the reinforcements are being tested by I.A.T. Ingegneria A&T and Earth System, companies focus on measurements for geotechnical, environmental and structural monitoring. Optical measurement technology by HBK FiberSensing supports monitoring of strain and temperature in the pre-stressed tie rods used for reinforcement.
Fiber Bragg Grating (FBG) sensors were glued to the Dywidag 32WR tie rods to measure strain and temperature at the same time. Each rod connector includes one array consisting of two bare FBGs – one for strain and another one for thermal compensation. When calibrated, the thermal compensation sensors provide absolute temperature values. To make things easier on site, the sensors were designed to be pre-installed at the HBK FiberSensing facilities and then transported to the site. The use of optical splitters simplified the installation of the system and optimize the interrogator’s capacity. Because the above mentioned arrays of FBGs are terminal (meaning that they are only connected on one side), optical splitters are used to combine the signals from several FBG arrays in one optical channel. The splitters used in this case allow 1x4 or 1x8 multiplexing.
Couplers for Dywidag 32WR tie rod
Installation of the FBG sensors
Finished sensor
Sensor packaging
The BraggMETER interrogator acquires all the different optical channels simultaneously at a rate of one sample per second (S/s). The 19’’ rack-mountable device used has eight optical channels. The FS22 Industrial BraggMETERs can be connected to a standard computer by Ethernet cable and controlled by BraggMONITOR software from HBK FiberSensing as well as through SCPI commands or via catman®. The fact that the static interrogator can actually operate as a stand-alone device and store data internally came in handy in this application. The interrogator was connected to a 3G router so that no computer was required on site. Data can be accessed remotely in the comfort of the office with the technician’s laptop.
Earth System is a design, production and marketing company in the field of instrumentation, data loggers and software for the acquisition, transmission and management of measurements for geotechnical, environmental and structural monitoring. Our business model is based entirely upon the quest for quality and innovation. Rigorous selection of our suppliers and quality control of the production processes enable us to offer instruments in line with the highest quality standards imposed by the market.
This will bring together HBM, Brüel & Kjær, nCode, ReliaSoft, and Discom brands, helping you innovate faster for a cleaner, healthier, and more productive world.
This will bring together HBM, Brüel & Kjær, nCode, ReliaSoft, and Discom brands, helping you innovate faster for a cleaner, healthier, and more productive world.
This will bring together HBM, Brüel & Kjær, nCode, ReliaSoft, and Discom brands, helping you innovate faster for a cleaner, healthier, and more productive world.
This will bring together HBM, Brüel & Kjær, nCode, ReliaSoft, and Discom brands, helping you innovate faster for a cleaner, healthier, and more productive world.
This will bring together HBM, Brüel & Kjær, nCode, ReliaSoft, and Discom brands, helping you innovate faster for a cleaner, healthier, and more productive world.