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MonVia Project, development and application of a new sensor box
MonVia Project, development and application of a new sensor box
IOMAC 2024 10th International Operational Modal Analysis Conference Naples,Italy
IOMAC 2024 10th International Operational Modal Analysis Conference Naples,Italy
A notable percentage of Italian bridges were built more than fifty years ago before the introduction of a seismic code. Although they do not meet the current technical code requirements, they are still part of the road or railway network. As some recent bridge collapses have demonstrated, all of these structures need attention, and modern and reliable continuous monitoring systems may represent a fundamental tool to identify the occurrence of damage or structural failure. MonVia Project has been funded by the Italian Ministry of Economic Development and one of the main outcomes of the research is the design and realization of a new multiparameter Sensor Box for continuous monitoring purposes of structures and infrastructures. The Sensor Box includes a high-sensitivity ultra-low noise tri-axial QMEMS accelerometer, a high accuracy bi-axial MEMS inclinometer and temperature, pressure and humidity sensors. The Sensor Boxes can be wire-connected, powered by switch PoE and synchronized by a GNSS/GPS-based PPS distributed system. A wireless data communication protocol is implemented for the data transfer and the Wi-Fi performance has been tested in the 200 sps high-flux scenario. Aiming to evaluate its performance, the system has been installed on a reinforced concrete arch bridge, playing a strategic role in the central road network of the city of Ragusa, southeastern Sicily. Although eastern Sicily is one of the most seismic-prone European areas, the bridge, built in 1964, was not designed to withstand seismic actions. In the paper, the performance of the continuous Ragusa bridge’s monitoring system for SHM is discussed, highlighting the pros and cons of the Sensor Box realized inside the MonVia project compared to a commercial device.
Aiming to define the permanent sensor layout, the bridge was identified by means of a two-day OMA campaign. The campaign was performed during daily and night hours with different levels of excitation due to the road traffic. By considering the five lower frequencies identified some considerations can be made. The first frequency (1.611 Hz) identifies along-axis flexural modal shapes that mainly involve the arch bridge. This aspect is crucial for verifying if the two joints disconnect the structures for the bending forces. The second frequency (1.719 Hz) denotes a flexural transversal behaviour. The third frequency (2.339 Hz) describes a vertical flexural shape that mainly involves the arches. Apparently, a significant unsymmetrical behaviour characterises the middle of the bridge, however additional investigations are needed to clarify this aspect. The fourth frequency (3.247Hz) identifies a second order transversal flexural modal shape defined by maxima displacements at the end of the viaducts. The fifth frequency (3.769Hz) identifies a second order longitudinal flexural modal shape. As a matter of fact, the campaign identified more than five frequencies. Three different numerical approaches have been developed during the project. In terms of first modal frequency, the DMEM approach returns 1.53 Hz, the 3D fem model 1.919Hz and the shell fem model 1.882Hz.
Aiming to define the permanent sensor layout, the bridge was identified by means of a two-day OMA campaign. The campaign was performed during daily and night hours with different levels of excitation due to the road traffic. By considering the five lower frequencies identified some considerations can be made. The first frequency (1.611 Hz) identifies along-axis flexural modal shapes that mainly involve the arch bridge. This aspect is crucial for verifying if the two joints disconnect the structures for the bending forces. The second frequency (1.719 Hz) denotes a flexural transversal behaviour. The third frequency (2.339 Hz) describes a vertical flexural shape that mainly involves the arches. Apparently, a significant unsymmetrical behaviour characterises the middle of the bridge, however additional investigations are needed to clarify this aspect. The fourth frequency (3.247Hz) identifies a second order transversal flexural modal shape defined by maxima displacements at the end of the viaducts. The fifth frequency (3.769Hz) identifies a second order longitudinal flexural modal shape. As a matter of fact, the campaign identified more than five frequencies. Three different numerical approaches have been developed during the project. In terms of first modal frequency, the DMEM approach returns 1.53 Hz, the 3D fem model 1.919Hz and the shell fem model 1.882Hz.
Comparison between the first modal shape of a) OMA campaign, b) HiStrA Macro-model, c) 3D FEM model, d) shell FEM model
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