Paper-Article |

UQ state-dependent framework for seismic fragility assessment of industrial components

Mon, 01 Sep 2025 00:00:00 +0000

Abstract

Recently, there has been increased interest in assessing the seismic fragility of industrial plants and process equipment. This is reflected in the growing number of studies, community-funded research projects and experimental campaigns on the matter. Nonetheless, the complexity of the problem and its inherent modelling, coupled with a general scarcity of available data on process equipment, has limited the development of risk assessment methods. In fact, these limitations have led to the creation of simplified and quick-to-run models. In this context, we propose an innovative framework for developing state-dependent fragility functions. This new methodology combines limited data with the power of metamodelling and statistical techniques, namely polynomial chaos expansions (PCE) and bootstrapping. Therefore, we validated the framework on a simplified and computationally efficient MDoF system endowed with Bouc–Wen hysteresis. Then, we tested it on a real nonstructural industrial process component. Specifically, we applied the state-dependent fragility framework to a critical vertical tank of a multicomponent full-scale 3D steel braced frame (BF). The seismic performance of the BF endowed with process components was captured by means of shake table campaign within the European SPIF project. Finally, we derived state-dependent fragility functions based on the combination of PCE and bootstrap at a greatly reduced computational cost.

Suggerimento

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Fragility models for industrial equipment subjected to natural hazards

Thu, 15 May 2025 00:00:00 +0000

Abstract

Large cylindrical storage tanks are widely utilised in petrochemical plants to store different liquid materials, e.g., crude oil. However, these structures are revealed to be especially vulnerable in case of a natural event like an earthquake or tsunami. Damage to these tanks, indeed, can lead to technology accidents (also known as NaTech), like a spill of dangerous materials or waste of filling, typically through failed sealings. To address the challenges of leakage modelling, fragility models associated to leakage due to seismic loading conditions of large cylindrical storage tanks, specifically a broad tank endowed with a single-deck floating roof, are studied. In particular, this paper aims to utilise a probabilistic model to evaluate fragility curves associated with leakage due to slosh-induced damage of single-deck floating roofs and/or seals of broad tanks. The assessment of failure mechanisms and leakage of pantograph-type mechanical seals is considered by means of local FE models. In addition, refined FE models of broad tanks with floating roofs are considered too. Specifically, a broad tank TK-59 endowed with an 86 m diameter and a 22 m height storing crude oil was selected and investigated as an industrial case study. Finally, fragility functions are derived and commented upon for the most relevant limit states associated with leakage.

Suggerimento

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Design standardisation and seismic protection of SMRs through modular metafoundations

Mon, 12 Feb 2024 00:00:00 +0000

Abstract

This paper investigates the seismic protection of the Nuward™ small modular reactor (SMR) building, focusing on design loading and beyond design basis earthquake (bDBE) conditions. The study aims to achieve two primary objectives: (i) to enhance seismic mitigation of a SMR building under bDBE conditions, through the use of the innovative modular single-layer (SLM) and multi-layer (MLM) metafoundations (MFs); (ii) to effectively standardise and harmonise SMR building designs in locations prone to beyond design basis conditions. To accomplish these goals and demonstrate the protective capabilities of the MFs, the study employs non-linear time-history analyses (NLTHAs) for both DBE and bDBE conditions. Along these lines, a reduced-order model was developed from a refined finite element (FE) model of the SMR building using the Craig-Bampton mode synthesis technique. Then, finite locally resonant modular MFs were designed and analysed using NLTHAs. Specifically, physics-based ground motion models (GMMs) were used to generate and select seismic triplets that mimicked DBE and bDBE scenarios for NLTHAs. Successively to achieve improved seismic performance, the optimization of the MFs was pursued by targeting the optimal number of columns, resonator parameters, and unit cell dimensions. Additionally, the deployment of inerters was considered, to significantly reduce the size of the MFs and enable their application in multiple layers for ultra-low frequency attenuation. The overall findings suggest that modular MFs meet seismic protection requirements, and positively contribute to the standardization process of SMR buildings, even in areas characterized by beyond-design seismic conditions.

Suggerimento

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Modelling of non-structural components of an industrial multi-storey frame for seismic risk assessment

Thu, 07 Sep 2023 00:00:00 +0000

Abstract

Seismic risk assessment of industrial facilities is complex due to the presence of different types of equipment. It represents a research issue that requires further investigation. To this end, some analytical approaches have been developed in the framework of performance-based earthquake engineering. Nonetheless, their accuracy in the case of complex critical facilities, such as nuclear and non-nuclear industrial plants, is still under investigation. Thus, the proposed study intends to research in depth, in a risk assessment framework, some critical aspects related to: (1) modelling of industrial facilities and their secondary equipment with different degrees of accuracy, also taking into account their dynamic interaction; (2) selection of seismic records for fragility analysis, due to the narrow distribution of frequency values for non-structural components; (3) effectiveness of performance-based earthquake engineering applied to this particular class of coupled structure-equipment for risk assessment. In this context, the proper selection of seismic records becomes relevant, and SCoRes, an innovative algorithm for accelerograms selection is worthy of investigation. On these premises, two different configurations of a primary industrial structure, i.e. a moment resisting frame and a braced frame, equipped with non-structural components and subjected to shake table test campaigns are selected as case studies. For the two configurations, a vulnerability assessment of two vertical tanks installed on the first floor was carried out. Along these lines, to establish the effectiveness of the proposed method for both the moment resisting frame and braced frame configurations, the mean annual frequency of exceedance of the bottom-wall strain of the above-mentioned tanks, both at the design basis and safe shutdown earthquake has been evaluated.

Suggerimento

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Experimental performance of a multi-storey braced frame structure with non-structural industrial components subjected to synthetic ground motions

Thu, 05 May 2022 00:00:00 +0000

Abstract

The seismic risk assessment of industrial facilities mainly relies on historical data and the analysis and design of uncoupled secondary components. Accordingly, the dynamic interaction between primary structures and process equipment is overlooked. The SPIF project - Seismic Performance of Multi-Component Systems in Special Risk Industrial Facilities - was carried out to respond to this gap, within the European H2020 SERA framework. Its objective regarded the investigation of the seismic behaviour of an archetype industrial multi-storey steel moment resisting frame (MRF) structure equipped with non-structural components (NSCs) by means of shaking table tests. The goal of the proposed study was to extend the interaction analysis between a primary multi-storey braced frame (BF) steel structure and NSCs in a performance-based earthquake engineering (PBEE) perspective. Along this vein, to excite the vibration periods of the NSCs and thus enhance possible coupling with the primary structure, a synthetic site-based ground motion model (GMM) was employed. More precisely, the proposed research intended: (i) to severely excite the process equipment and supplement the scarcity of real records with a specific frequency content by means of a stochastic GMM; (ii) to quantify seismic-induced force and displacement demands of secondary components and their effects on the primary BF structure. The evaluation of the experimental data clearly shows buckling in the bracing system of the BF configuration and a strong interaction between vertical tanks and floor crossbeams of the BF. At the very least, the favourable performance of the archetype BF under strong seismic records is demonstrated.

Suggerimento

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Seismic performance of an industrial multi-storey frame structure with process equipment subjected to shake table testing

Wed, 01 Sep 2021 00:00:00 +0000

Abstract

Past earthquakes demonstrated the high vulnerability of industrial facilities equipped with complex process technologies leading to serious damage of process equipment and multiple and simultaneous release of hazardous substances. Nonetheless, current standards for seismic design of industrial facilities are considered inadequate to guarantee proper safety conditions against exceptional events entailing loss of containment and related consequences. On these premises, the SPIF project - Seismic Performance of Multi-Component Systems in Special Risk Industrial Facilities - was proposed within the framework of the European H2020 SERA funding scheme. In detail, the objective of the SPIF project is the investigation of the seismic behaviour of a representative industrial multi-storey frame structure equipped with complex process components by means of shaking table tests. Along this main vein and in a performance-based design perspective, the issues investigated in depth are the interaction between a primary moment resisting frame (MRF) steel structure and secondary process components that influence the performance of the whole system; and a proper check of floor spectra predictions. The evaluation of experimental data clearly shows a favourable performance of the MRF structure, some weaknesses of local details due to the interaction between floor crossbeams and process components and, finally, the overconservatism of current design standards w.r.t. floor spectra predictions.

Suggerimento

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Bolted flange joints equipped with FBG sensors in industrial piping systems subjected to seismic loads

Sat, 26 Jun 2021 00:00:00 +0000

Abstract

The vulnerability of major-hazard industrial plants to natural hazards has been recognized as an emergent issue whose importance is underlined by the Sendai Framework, established immediately after the Tohoku earthquake of 2011, in Japan. Hence, seismic risk analysis is of paramount importance as testified by the intense research activity that characterized the last years. In this respect, structural health monitoring can represent a valuable tool able to strongly help the decision-making phase. Along this main vein, optical fibers (OFs) represent a class of sensors able to both monitor critical conditions, as leakage of hazardous material, and activate safety barriers, if any. More precisely, optical fibers represent an economic solution, whose characteristics appear particularly suitable for dangerous environments like major-hazard plants. However, investigations relevant to their use for seismic monitoring of chemical/petrochemical plants are rather limited, especially when subject to strong dynamic excitations. As a result, this paper deals with the analysis of optical fiber Bragg gratings (FBGs) applied to bolted flange joints (BFJ) under cyclic loadings. More precisely, two experimental programs, i.e., a cyclic test on a single BFJ and a series of shaking table tests on BFJs of a multicomponent system, demonstrated the effectiveness of the proposed monitoring systems in detecting hazardous conditions and, thus, their potential use in conjunction with safety barriers.

Suggerimento

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