A framework for probabilistic seismic risk assessment of NG distribution networks

Lifelines are essential infrastructures for human activities and the economic developm ent of a region. Lifelines vulnerability reduction is an actual question, particularly with reference to NaTech events, like earthquakes. In this regard, worldwide past seismic experiences revealed heavy damages to NG distribution networks. It is therefore essential to perform seismic risk assessment of NG buried pipelines systems with the aim to identify potential criticalities and avoid significant consequences. For such reasons, this work illustrates the proposal of a probabilistic framework for seismic risk assessment of NG lifelines. The proposed procedure is subsequently applied to a specific case study in Italy to highlight its feasibility

Analysis of Natech Risk for Pipelines: A Review

Natural events, such as earthquakes and floods, can trigger accidents in oil and gas pipeline with potentially severe consequences to the population and to the environment. These conjoint technological and natural disasters are termed natech accidents. The present literature review focuses on the risk analysis state‐of‐the‐art of seismic and flood events that can impact oil and gas transmission pipelines. The research has focused on methodologies that take into account the characteristics of natech events: for instance, the characterization of the triggering natural hazard and the final accident scenarios, as well as fragility curves for the specific assessment of the potential consequences of natech accidents. The result of this research shows that the literature on seismic risk analysis offers the largest number of examples and methodologies, although most studies focused on structural damage aspects without considering the consequences of a potential loss of containment from the pipelines. Very little work was found on flood risk assessment of natech events in pipelines.JRC.G.6-Security technology assessmen

GIS-based method to assess seismic vulnerability of interconnected infrastructure: A case of EU gas and electricity networks

Our study concerns the interconnected European Electricity and Gas transmission grid where we address two important issues of these interdependent critical infrastructures. First we assessed the response under seismic hazard for each independent network; then we analysed the increased vulnerability due to coupling between these two heterogeneous networks. We developed a probability reliability model that encompasses the spatial distribution of the network structures using a Geographic Information System (GIS). We applied the seismic risk assessment of individual network facilities and presented the results in the form of the system fragility curves of the (independent and dependant) networks in terms of various performance measures - connectivity loss, power loss, and impact on the population. We characterized the coupling behaviour between the two networks as a physical dependency: here the electricity grid, in part, depends on the gas network due to the generation capacity of gas-fired power plants. The dependence of one network on the other is modelled with an interoperability matrix, which is defined in terms of the strength of coupling; additionally we consider how the mechanical-structural fragility of the pipelines of the gas-source supply stream contributes to this dependence. In addition to network-wide assessment, damage was also evaluated at a local level by examining the performance status of each and every electricity distribution substation in the electricity grid. Finally, the comprehensive geographical distributions of performance loss at the European level can be visualized on a GIS tool; showing, as expected, that the highest direct damage in southeast Europe.JRC.DG.G.5-European laboratory for structural assessmen

A critical review on the vulnerability assessment of natural gas pipelines subjected to seismic wave propagation. Part 1:Fragility relations and implemented seismic intensity measures

© 2019 Elsevier Ltd Natural gas (NG) pipeline networks constitute a critical means of energy transportation, playing a vital role in the economic development of modern societies. The associated socio-economic and environmental impact, in case of seismically-induced severe damage, highlights the importance of a rational assessment of the structural integrity of this infrastructure against seismic hazards. Up to date, this assessment is mainly performed by implementing empirical fragility relations, which associate the repair rate, i.e. the number of repairs/damages per unit length of the pipeline, with a seismic intensity measure. A limited number of analytical fragility curves that compute probabilities of failure for various levels of predefined damage states have also been proposed, recently. In the first part of this paper, a thorough critical review of available fragility relations for the vulnerability assessment of buried NG pipelines is presented. The paper focuses on the assessment against seismically-induced transient ground deformations, which, under certain circumstances, may induce non-negligible deformations and strains on buried NG pipelines, especially in cases of pipelines crossing heterogeneous soil sites. Particular emphasis is placed on the efficiency of implemented seismic intensity measures to be evaluated or measured in the field and, more importantly, to correlate with observed structural damage on buried NG pipelines. In the second part of this paper, alternative methods for the analytical evaluation of the fragility of steel NG pipelines under seismically-induced transient ground deformations are presented. Through the discussion, recent advancements in the field are highlighted, whilst acknowledged gaps are identified, providing recommendations for future research

Guidelines for typology definition of European physical assets for earthquake risk assessment

It is an essential step in urban earthquake risk assessment to compile inventory databases of elements at risk and to make a classification on the basis of pre-defined typology/taxonomy definitions. Typology definitions and the classification system should reflect the vulnerability characteristics of the systems at risk, e.g. buildings, lifeline networks, transportation infrastructures, etc., as well as of their sub-components in order to ensure a uniform interpretation of data and risk analyses results. In this report, a summary of literature review of existing classification systems and taxonomies of the European physical assets at risk is provided in Chapter 2. The identified main typologies and the classification of the systems and their sub-components, i.e. SYNER-G taxonomies, for Buildings, Utility Networks, Transportation Infrastructures and Critical Facilities are presented in Chapters 3, 4, 5 and 6, respectively.JRC.G.5-European laboratory for structural assessmen

Assessment of Failure Frequencies of Pipelines in Natech Events Triggered by Earthquakes

During a seismic event, underground pipelines can undergo to significant damages with severe implications in terms of life safety and economic impact. This type of scenarios falls under the definition of Natech. In recent years, quantitative risk analysis became a pivotal tool to assess and manage Natech risk. Among the tools required to perform the quantitative assessment of Natech risk, vulnerability models are required to characterize equipment damages from natural events. This contribution is focused on the review of the pipeline vulnerability models available for the case of earthquakes. Two main categories of models have been identified in the literature. A first category proposes the repair rate as performance indicator for the damage of pipeline due to seismic load, and gives as output the number of required repairs per unit length. A second category proposes fragility curves associated with risk states depending on the mechanism of ground failure. In the framework of Natech risk assessment, the latter have the important advantage of having clearly and unambiguously defined the risk status (and thus the extent of the release) with which they are associated. A subset of vulnerability models deemed more appropriate to be applied in the framework of Natech risk assessment is then identified. Their application to the assessment of the expected frequencies of release events due to pipeline damage is provided, enabling their comparison and the discussion of the relative strengths and weaknesses

Seismic Evaluation and Retrofit of a Major Natural Gas Transmission System

The performance of pipeline systems under seismic loading is an important consideration in regions subject to earthquakes. Experience from previous seismic events indicates that earthquake-induced permanent ground displacements are one of the key geotechnical hazards to pipelines. This paper briefly describes an evaluation of the vulnerability of a natural gas transmission system to seismic hazards, along with some of the remedial treatments that were implemented. The work was carried out for BC Gas Utility Ltd. in the Lower Mainland of British Columbia, Canada. Initially, a regional study was carried out to identify components of the gas pipeline system that are seismically most vulnerable. Following the regional study, the most vulnerable sites were identified for detailed site-specific analyses with the objective of developing remedial treatment alternatives. Two case histories are described to illustrate some of the options available for seismic upgrading of pipeline systems. The first case history describes a project where ground densification by vibro-replacement was used to reduce the risk of ground deformations at an existing gate station. The second case history describes a project where a new pipeline was installed using the method of horizontal directional drilling (HDD) to avoid potentially liquefiable zones