The catastrophic consequences of recent NaTechevents triggered by earthquakes highlighted the inadequacy of standard approaches to seismic risk assessment of chemical process plants. To date, the risk assess- ment of such facilities mainly relies on historical data and focuses on uncoupled process components. As a consequence, the dynamic interaction between process equipment is neglected. In response to this gap, researchers started a progressive integration of the Paciﬁc Earthquake Engineering Research Center (PEER) Performance-Based Earthquake Engineering (PBEE) risk assessment framework. However, a few limitations still prevent a systematic implementation of this framework to chemical process plants. The most signiﬁcant are: i)thecomputationalcostofsystem-levelsimulationsaccountingforcouplingbetweenprocessequipment; ii) the experimental cost for component-level model validation; iii) a reduced number of hazard-consistent site-speciﬁc ground motion records for time history analyses. In response to these challenges, this paper proposes a recently developed uncertainty quantiﬁcation-based framework to perform seismic fragility assessments of chemical process plants. The framework employs three key elements: i) a stochastic ground-motion model to supplement scarcity of real records; ii) surrogate modelingtoreducethecomputationalcostofsystem-levelsimulations; iii)acomponent-levelmodelvalidation based on cost-eﬀective hybrid simulation tests. In order to demonstrate the potential of the framework, two fragility functions are computed for a pipe elbow of a coupled tank-piping system. Keywords: Seismic fragility analysis; PEER-PBEE framework; Artiﬁcial ground motion; Surrogate mod- eling; Hybrid simulation; Tank-piping system. 1 Introduction Campedel[1]showedthatnaturalhazardsareonetheleadingcauseofChemicalProcessPlants(CPP)accidents. The study is based on an extensive review of historical data based on ﬁve European and one US databases. Kidam and Hurme [2] found similar ﬁgures by analyzing 364 CPP accidents from the Japanese Failure Knowl- edge Database. Such occurrences are classiﬁed as NaTechevents, that is, technological accidents triggered by natural disasters. Release of hazardous chemicals, ﬁre, or explosions following a structural failure are often among the most signiﬁcant consequences of NaTech events [3, 4]. The Izmit reﬁnery ﬁre following the Kocaeli earthquake (Turkey, 1999) [5], the leak of hazardous chemicals from multiple fertilizer plants following the Wenchuan earthquake (China, 2008) [6], and the nuclear accident following the Fukushima earthquake-induced Tsunami (Japan, 2011) [7] are just some examples of NaTech events associated with seismic hazard. Their catastrophic consequences have highlighted the inadequacy of standard approaches to risk assessment of CPPs. These approaches mainly relies on expert opinion or historical data [8, 9, 10, 11]. Moreover, they are performed at the component level; thus, neglecting system-level interactions with other CPP components [12]. This lack of system-level numerical simulations has been recognized as one of the major research gaps in the current literature. Corresponding Author: Dr. Giuseppe Abbiati, abbiati@eng.au.dk , ORCID: 0000-0002-5048-8505 . 1 DRAFTInresponsetothisresearchgap,inthelastdecade,researchersstartedaprogressiveintegrationofperformance- based risk analysis frameworks [13]. In the seismic risk context, the natural choice was directed towards the PEER-PBEE approach [14, 15]. In essence, the PEER-PBEE framework uses the total probability theorem to decompose the quantiﬁcation of seismic risk into diﬀerent tasks, which can be handled by diﬀerent groups of experts. In detail, the tasks are: i) probabilistic seismic hazard analysis (PSHA); ii) fragility analysis; iii) damage analysisy; iv) loss analysis. Within this perimeter, fragility analysis of CPPs has become an active research ﬁeld. As an example, Hosseini et.al.[16] computed fragility surfaces for oil reﬁnery piping systems, and Mebarki et.al.[17] derived fragilityandrecoveryfunctionsforatmosphericindustrialtanks. Inaddition,diﬀerentresearchgroupsdeveloped system-level numerical simulations for fragility analysis of liqueﬁed natural gas plants [18, 19, 20]. Finally, examples of coupled analysis can be found in [21, 22, 23]. In all these cases, fragility functions are evaluated using a set of suitable ground motions, which are used as input for nonlinear structural analysis [24, 25, 26]. In the context of seismic fragility, Bradley [27] and et al.[28] collected a number of open issues. Although both studies refer to the seismic risk of civil structures, their conclusions are also valid for CPPs. Speciﬁcally, the authors highlighted the following three criticalities: Although methodologies for ground motion selection succeed in describing seismic hazard for a given structural system, the number of available records is usually too small for computing accurate statistics of response quantities of interest (QoI). Experimental validation of system components is often overlooked, and this is due to practical reasons. Structural testing is usually not aﬀordable beyond the component level due to the limited capacity of experimental facilities. The computation of fragility analysis requires a large number of time history analyses. It follows that computational expensive structural simulators limit de facto the total number of simulations. Recently, Abbiati et al.[29] proposed a comprehensive framework that tackles these open challenges. This study adopts and applies this framework to compute the seismic fragility analysis of a tank-piping system of an ideal CPP. Thebuildingblocksofthecomputationalframeworkareanartiﬁcialgroundmotion(AGM)modelcalibrated against hazard-compatible site-speciﬁc seismic records (e.g., the AGM model of Rezaian and Der Kiureghian in thisstudy[30]), ahigh-ﬁdelity(HF)structuralsimulatorofthe