Abstract Summary
The improvements in the development of reliable and low-cost sensors, capable of measuring different structural response quantities (e.g. acceleration, strain, etc.) have attracted extensive research in the field of Structural Health Monitoring (SHM) over the last decades. However, despite the advancements in the field, SHM has not been yet translated to extensive full-scale applications on real structures and infrastructures. In parallel, in the last few years, new paradigms such as the Internet of Things (IoT) have gained a lot of attention in both industry and academia. Fundamental enabling technology for the IoT framework is the fifth generation (5G) network, a solution conceived to satisfy the increasing demand of mobile data traffic and meet the stringent requirements of the emerging IoT applications. Among the many emerging applications that can potentially rely on a 5G communication network and exploit IoT solutions, great interest has emerged in SHM applications on critical structures and infrastructures, since unfortunate recent events have drawn primary attention to the challenges related to public roads safety. Starting from this premises, the present paper describes the pilot application of a new wireless accelerometric prototype to an ongoing structural monitoring activity over a very common kind of prestressed concrete bridge in Italy. The infrastructure under investigation is located in a small town near Genoa, Northern Italy. It is a 200 m long beam bridge with 27 m span. It has been equipped with a monitoring system including environmental and structural response sensors. A meteorological station is installed on a lighting column recording wind speed, atmospheric pressure, temperature and humidity with a sampling frequency of 1 Hz. Structural response is recorded by six triaxial MEMS accelerometers, placed on the outer beams of the first two spans, characterized by 100 Hz sampling rate. For accelerometric data acquisition and transmission, in this work we propose a low-cost, versatile and self-sustaining hardware prototype based on the Narrow-Band IoT (NB-IoT) technology. Each sensor is connected to a Raspberry Pi 4 (RPi4) for real-time edge processing of the collected signals. The RPi4s are equipped with a 5G module, allowing the system to connect the remote nodes by exploiting the cellular network infrastructure through NB-IoT technology without the need of ad-hoc connectivity. Data from the sensors are recorded continuously since October 2022. Identification of the dynamic properties of the structure is carried out through output-only operational modal analysis (OMA) techniques. Results are compared with the outcomes of the tests performed in a preliminary phase of the experimental activity, when classical cabled accelerometers were used. In addition, the variability of bridge’s dynamic characteristics is investigated in near real-time for different environmental and operational conditions, representing the first step of a potential SHM application for the active maintenance of the infrastructure. The research presented in this paper has been developed in the framework of the project ”5G SMART ROADS PER GENOVA” (5GSMARTG), partially funded by the Italian Ministry of Economic Development (MiSE).
