PSI - Issue 44

Mariano Ciucci et al. / Procedia Structural Integrity 44 (2023) 347–354

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Mariano Ciucci et al. / Structural Integrity Procedia 00 (2022) 000–000

Off-site systems can be integrated by low cost on site sensors like lower-resolution strong motion seismometers. These sensors use micro-electro-mechanical systems accelerometers. These low-cost sensors can be hosted in industrial sites, providing, “live” information and activating automatic alert and mitigation systems. It is easy to recognize that the greater the early warning time is, the stronger the possibility of preventing damages to plant installations and possibly mitigating the effects of an earthquake (see Fig. 2). 4. Structural/Process Early Warning Systems The use of smart sensors-based technology integrated with existing safety sensors, generally present in major hazard industrial plants can represents an interesting mitigation strategy option. In particular, to reduce the risk in case of major accidents and control the consequences of seismic NaTech events, both the use of ad hoc monitoring and control systems (Marino et al 2017) and the implementation of smart technologies sensors, actuators and innovative systems for seismic protection can be pursued. For this purpose, various types of sensors can be used, which are often integrated into specific systems for structural monitoring and identification of the release of dangerous substance. Their application is generally confined to structural health monitoring (SHM: Structural Health Monitoring), but they can also be applied in case of earthquakes. This kind of systems are called Structural/Process Early Warning (EW) and imply the use of sensors for the identification and control of the release of substances, but also of sensors for the evaluation of seismic intensity level in real-time. The advantages in using these systems are clear: the permanent monitoring of critical components of a plant allows, on one hand to plan the maintenance operations, and on the other hand to develop decision-making systems able to limit the consequences in case of seismic events. These Early Warning (EW) sensors can be implemented in a smart system and linked to PCS (process control system) in order to detect immediately the effects of an earthquake on industrial plant components and eventually to activate automatically safety systems aimed at controlling major-accident hazards and at limiting consequences. These sensor are often used in wireless networks. 4.1. Deformations and displacements sensors This group includes sensors capable of measuring deformation in a point of the structure, in real time. They are resistive in nature and generally have a high measurement sensitivity (see Fig. 3). They need to be installed in specific points of the structure where major deformations are expected; therefore, their installation require a preliminary structural study. Strain gauges and linear potentiometers belong to this family. They generally require a permanent in situ acquisition system, capable of continuously reading deformations.

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Fig. 3. a) strain gauges; b) electrical extensometers.

4.2. Acceleration sensors In order to monitor the seismic response of structures, sensors for acceleration measurements can be usefully employed, acting at the same time as seismic early warning systems (see Fig. 4). The micro-electromechanical system (MEMS) technology can reduce the costs of these sensors, and nowadays allows to produce accelerometers contained in a single chip. Moreover, these sensors can operate in a wireless environment.