PSI - Issue 78

Alessandra Marino et al. / Procedia Structural Integrity 78 (2026) 1753–1758

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1. Introduction The impact of a natural disaster on a facility storing or processing dangerous substances can result in the release of those hazardous substances with possible severe off-site consequences through toxic release, fire or explosion scenarios. Accidents triggered by a natural hazard, involving release of dangerous substances are commonly referred to as NaTech events. These include releases from fixed chemical installations and spills from oil and gas pipelines. One of the main issues of NaTech accidents is the simultaneous occurrence of a natural disaster and a technological accident; both require simultaneous efforts in dealing with a situation in which lifelines designed for a disaster mitigation are likely unavailable, as they may have been damaged by the natural disaster. In addition, hazardous substances releases may occur from single or multiple sources, resulting in multiple chains of accidents in the same installation, or in different plants, requiring emergency management resources that unfortunately could be engaged in responding to the natural disaster in other situations. Despite of a recognized growing of the research activities that resulted in more strict regulations for the design of industrial activities, NaTech accidents remain an emerging threat. The Directive 2012/18/EU of the European Parliament and of the council of 4 July 2012 on the control of major-accident hazards involving dangerous substances (Directive 2012/18/EU), implemented by the member states, recognized the relevance of NaTech events. The implementation of smart technologies (sensors, actuators, innovative systems for seismic protection) to the critical elements of a plant allows the reduction of major hazards and related consequences because it provides simultaneous monitoring and control of natural and technological events. Smart systems should be implemented in the design of new industrial facilities to improve safety performance. On the other hand, smart systems allow to upgrade the safety conditions of existing industrial plants implemented as a retrofit solution, avoiding heavy and expensive structural actions. Smart systems could certainly contribute in reducing risk and mitigate consequences of major accidents. The object of this paper is to provide a clear framework of the technologies to be employed as

smart systems particularly in reducing the seismic risk of major-hazard industrial plants. 2. Seismic vulnerability of critical elements in major hazard industrial plants

Natech events derives from the interaction between industrial and natural hazards. In particular, earthquakes have been recognized as one of the most disruptive natural hazards, as demonstrated by many past earthquakes, which raised public concern because of the general unpreparedness of the countries in predicting effects and consequences in the aftermath of a disaster. In order to identify the best solutions (e.g. SMART sensors) a detailed analysis of the critical conditions that are typically present in process plant units is needed. According to the structural classification of the process plant units the components that can be subjected to major damages and generate serious consequences are the following:

• Slim vessels (columns, pressure vessels) • Above ground squat equipment (large tanks) • Squat and slender equipment supported by column (elevated tanks, Furnaces, etc.) • Piping systems and support structures

During the seismic action the major structural deficiencies of columns is represented by weakness of skirt against buckling phenomena and failure of the anchors. Large deformation of the column could cause excessive rotation in the bolt flanged joints between the columns and the inlet and outlet pipes. The failure of the skirt could generate the structural collapse with the instantaneous release of the full content. Excessive rotation of the flanged joints is related to minor releases. Pressure vessels (tanks, separators, etc.) belongs also to the category of slim vessel. In this case the problem is usually generated by the failure of the saddles as evidenced in many occasions or by the rupture of the anchors. In this case, the release of the full content could take place. Above ground squat equipment category are well represented by large tanks. Most frequent damage state under seismic loading is the elasto-plastic (elephant foot) buckling, which could produce high plastic deformations at the