Sanghyun Park, Hyonjeong Noh, Su-gil Cho, Kwangu Kang
The CO2 intermediate storage terminal play an important role in transporting the CO2 transported through the CO2 carrier to the subsea pipeline. In the case of large-scale CO2 intermediate storage terminal, there are inherent hazard factors, which can lead to significant property loss and human damage in the event of an accident. In this regard, in order to ensure the safety of CO2 intermediate storage terminal, the internationally certified safety assessment technique should be introduced. In this research, although the CO2 intermediate storage terminal is composed of various subsystems, we only consider CO2 storage tank among various subsystems. Since the CO2 storage tank stores a large amount of CO2, when the tank itself is ruptured, overpressure, low pressure, overcharging, etc., it may cause great damage due to a large amount of CO2 leakage. We perform the Layer of Protection Analysis (LOPA) for CO2 storage tank so as to achieve the functional safety required by the international standards. The LOPA provides the results of quantitative analysis whether the safety system about the hazard scenarios can ensure the risk within an acceptable risk level. In this research, through the LOPA of CO2 storage tank, we evaluate the safety of conventional system and identify the required safety level for the additional safety system.
{"title":"LAYER OF PROTECTION ANALYSIS FOR CO2 STORAGE TANK","authors":"Sanghyun Park, Hyonjeong Noh, Su-gil Cho, Kwangu Kang","doi":"10.2495/RISK180201","DOIUrl":"https://doi.org/10.2495/RISK180201","url":null,"abstract":"The CO2 intermediate storage terminal play an important role in transporting the CO2 transported through the CO2 carrier to the subsea pipeline. In the case of large-scale CO2 intermediate storage terminal, there are inherent hazard factors, which can lead to significant property loss and human damage in the event of an accident. In this regard, in order to ensure the safety of CO2 intermediate storage terminal, the internationally certified safety assessment technique should be introduced. In this research, although the CO2 intermediate storage terminal is composed of various subsystems, we only consider CO2 storage tank among various subsystems. Since the CO2 storage tank stores a large amount of CO2, when the tank itself is ruptured, overpressure, low pressure, overcharging, etc., it may cause great damage due to a large amount of CO2 leakage. We perform the Layer of Protection Analysis (LOPA) for CO2 storage tank so as to achieve the functional safety required by the international standards. The LOPA provides the results of quantitative analysis whether the safety system about the hazard scenarios can ensure the risk within an acceptable risk level. In this research, through the LOPA of CO2 storage tank, we evaluate the safety of conventional system and identify the required safety level for the additional safety system.","PeriodicalId":21504,"journal":{"name":"Risk Analysis XI","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75547120","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The transportation of dangerous goods/hazardous chemicals is a hot issue in the area of industrial safety. This paper investigates route optimization for the transportation of Adipic acid based on the fuzzy compromise approach and the iterative algorithm, proposing a multi-point multi-objective decisionmaking model of road transportation routing with minimum transportation risk, minimum transportation cost and minimum sensitive population. The three objective functions are integrated with weights by path optimization and risk decision model. The optimal compromised solution is obtained using the extended label correcting method. The iterative algorithm is used to remove the road section with maximum risk and get the final optimized route. The final optimized route is obtained by multiple optimizations, which combines the dual advantages of extended label correcting method and the iterative algorithm. Compared with the optimized route obtained by only using one-off optimization, the proposed method can consider the weight of the multi-objective functions to better balance the relationship among different objectives and is better to meet the requirement of the government, the transporters and the general public. An example is used to demonstrate the model. Using the route optimization model proposed in this paper, it is feasible to acquire a good balance between the risks and benefits associated with hazardous chemical transportation.
{"title":"A MULTI-POINT MULTI-OBJECTIVE TRANSPORTATION ROUTE-OPTIMIZATION MODEL OF HAZARDOUS CHEMICALS","authors":"Jingna Li, Jinghong Wang, Youran Zhi, Xuhai Pan","doi":"10.2495/RISK180251","DOIUrl":"https://doi.org/10.2495/RISK180251","url":null,"abstract":"The transportation of dangerous goods/hazardous chemicals is a hot issue in the area of industrial safety. This paper investigates route optimization for the transportation of Adipic acid based on the fuzzy compromise approach and the iterative algorithm, proposing a multi-point multi-objective decisionmaking model of road transportation routing with minimum transportation risk, minimum transportation cost and minimum sensitive population. The three objective functions are integrated with weights by path optimization and risk decision model. The optimal compromised solution is obtained using the extended label correcting method. The iterative algorithm is used to remove the road section with maximum risk and get the final optimized route. The final optimized route is obtained by multiple optimizations, which combines the dual advantages of extended label correcting method and the iterative algorithm. Compared with the optimized route obtained by only using one-off optimization, the proposed method can consider the weight of the multi-objective functions to better balance the relationship among different objectives and is better to meet the requirement of the government, the transporters and the general public. An example is used to demonstrate the model. Using the route optimization model proposed in this paper, it is feasible to acquire a good balance between the risks and benefits associated with hazardous chemical transportation.","PeriodicalId":21504,"journal":{"name":"Risk Analysis XI","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81637730","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Kukovica, S. Molnar, H. Ghofrani, K. Assatourians
The Leech River fault (LRF) is situated on Vancouver Island near the city of Victoria, British Columbia, Canada. The transpressional reverse fault zone is present at surface for a length of ~60 km east to west along the southern tip of Vancouver Island. Recent paleoseismic evidence suggests at least two surfacerupturing events to have exceeded a moment magnitude (M) of 6 within the last 15,000 years. This fault system poses considerable seismic hazard due to its proximity to Victoria and three hydroelectric dams. We performed Probabilistic Seismic Hazard Analyses (PSHA) and Deterministic Seismic Hazard Analyses (DSHA) for Victoria with consideration of an active LRF zone. We first calibrate our PSHA methodology and successfully replicate the 2015 National Building Code of Canada (NBCC) uniform hazard spectrum for a 2% probability of exceedance in 50 years. We add an active LRF zone with magnitude recurrence parameters based on faultand region-specific seismicity catalogues. Ground motions are calculated for the synthetic fault earthquake catalogue using Ground Motion Prediction Equations (GMPEs) based on western Canada crustal source zones (hypocentral distance metric) and fault source zones (projected fault plane distance metric). We observe up to 0.32 factor increase in the predicted motions at a frequency of 10 Hz utilizing crustal GMPEs and 2.65 factor increase utilizing fault GMPEs at 1 Hz. The DSHAs are accomplished using finite-difference 3D wave propagation simulations of a M 6.8 rupture with different hypocentral locations and fault geometry. The lowfrequency simulations demonstrate ~20 cm/s peak ground velocity (strong shaking) is expected in Greater Victoria. Previous studies that examined economic losses in Victoria for M 6 or 7 Leech River fault scenario earthquakes estimate 2.5 billion to 8.5 billion Canadian dollar losses, respectively.
{"title":"IMPACT FROM A NEARBY SEISMICALLY-ACTIVE FAULT TO SEISMIC HAZARD IN VICTORIA, CANADA","authors":"J. Kukovica, S. Molnar, H. Ghofrani, K. Assatourians","doi":"10.2495/RISK180151","DOIUrl":"https://doi.org/10.2495/RISK180151","url":null,"abstract":"The Leech River fault (LRF) is situated on Vancouver Island near the city of Victoria, British Columbia, Canada. The transpressional reverse fault zone is present at surface for a length of ~60 km east to west along the southern tip of Vancouver Island. Recent paleoseismic evidence suggests at least two surfacerupturing events to have exceeded a moment magnitude (M) of 6 within the last 15,000 years. This fault system poses considerable seismic hazard due to its proximity to Victoria and three hydroelectric dams. We performed Probabilistic Seismic Hazard Analyses (PSHA) and Deterministic Seismic Hazard Analyses (DSHA) for Victoria with consideration of an active LRF zone. We first calibrate our PSHA methodology and successfully replicate the 2015 National Building Code of Canada (NBCC) uniform hazard spectrum for a 2% probability of exceedance in 50 years. We add an active LRF zone with magnitude recurrence parameters based on faultand region-specific seismicity catalogues. Ground motions are calculated for the synthetic fault earthquake catalogue using Ground Motion Prediction Equations (GMPEs) based on western Canada crustal source zones (hypocentral distance metric) and fault source zones (projected fault plane distance metric). We observe up to 0.32 factor increase in the predicted motions at a frequency of 10 Hz utilizing crustal GMPEs and 2.65 factor increase utilizing fault GMPEs at 1 Hz. The DSHAs are accomplished using finite-difference 3D wave propagation simulations of a M 6.8 rupture with different hypocentral locations and fault geometry. The lowfrequency simulations demonstrate ~20 cm/s peak ground velocity (strong shaking) is expected in Greater Victoria. Previous studies that examined economic losses in Victoria for M 6 or 7 Leech River fault scenario earthquakes estimate 2.5 billion to 8.5 billion Canadian dollar losses, respectively.","PeriodicalId":21504,"journal":{"name":"Risk Analysis XI","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89427155","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Failures of wood-framed residential structures are among the most common and expensive types of wind damage in densely populated regions. Numerous recent studies have focused on mitigating residential damage during tornadoes and hurricanes. Past work has identified weak links in the vertical load path of wood-framed homes under uplift, focusing primarily on the roofs since their failure is common. In recent work, structural details such as connections and fasteners have been determined to have a large impact on the resilience of wood-framed homes. In this paper, common residential failure modes are reviewed, ongoing work to prevent expensive residential damage is presented, and failure wind speed estimates currently used in tornado assessment are revisited. The results of preliminary structural analyses verify the common understanding that toe-nailed roof-to-wall connections are likely to be among the most vulnerable elements in the structure of a wood-framed house. However, it is also found that certain framing members and connections display significant vulnerability under the same wind uplift, and the possibility of framing failure is not to be discounted. The analysis results and damage survey observations are used to expand the understanding of wood-framed residential roof failures, as they relate to the Enhanced Fujita scale, and address potential gaps in current residential construction practice.
{"title":"PERFORMANCE OF WOOD-FRAMED RESIDENTIAL STRUCTURES UNDER EXTREME WIND LOADS","authors":"Sarah A. Stevenson, G. Kopp, A. M. E. Ansary","doi":"10.2495/RISK180161","DOIUrl":"https://doi.org/10.2495/RISK180161","url":null,"abstract":"Failures of wood-framed residential structures are among the most common and expensive types of wind damage in densely populated regions. Numerous recent studies have focused on mitigating residential damage during tornadoes and hurricanes. Past work has identified weak links in the vertical load path of wood-framed homes under uplift, focusing primarily on the roofs since their failure is common. In recent work, structural details such as connections and fasteners have been determined to have a large impact on the resilience of wood-framed homes. In this paper, common residential failure modes are reviewed, ongoing work to prevent expensive residential damage is presented, and failure wind speed estimates currently used in tornado assessment are revisited. The results of preliminary structural analyses verify the common understanding that toe-nailed roof-to-wall connections are likely to be among the most vulnerable elements in the structure of a wood-framed house. However, it is also found that certain framing members and connections display significant vulnerability under the same wind uplift, and the possibility of framing failure is not to be discounted. The analysis results and damage survey observations are used to expand the understanding of wood-framed residential roof failures, as they relate to the Enhanced Fujita scale, and address potential gaps in current residential construction practice.","PeriodicalId":21504,"journal":{"name":"Risk Analysis XI","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73058979","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Old dams were usually constructed using simplified design criteria. Seismic action was not totally computed and included in the dams’ sizing procedure, mainly static forces were applied to the dam body and resistance to a seismic excitation of 0.1 g peak ground acceleration was verified. This can raise stability concerns because, according to its location, the dam could be subjected to stronger earthquakes. The Qaraoun concrete face rockfill dam (CFRD), the first Lebanese dam, built in 1964, is studied here to evaluate overall stability. The highest excitation predicted for the site is defined by seismic hazard assessment, the applied earthquake is the horizontal component of the Tabas earthquake that occurred in Iran in 1978, with a 7.4 magnitude and 0.8 g ground acceleration, since the specifications of such an earthquake match the required design solicitation. The simulation was performed using the finite element code Plaxis 2D; a numerical model is presented with all calibration steps and assumptions covering the lack of data regarding the materials’ properties. A non-linear behaviour was adopted for the rock fill; static and dynamic calculations were performed in order to obtain the permanent deformations, allowing for a judgement regarding the stability of the dam. A final settlement of one metre at the crest and a horizontal displacement of one metre are not threatening values, taking into consideration the level of the reservoir free board, which is 5 m below the dam crest.
{"title":"RESPONSE OF A LEBANESE ROCK-FILLED DAM TO SEISMIC EXCITATION","authors":"Sobhi Almawla, F. H. Chehade, F. Kaddah","doi":"10.2495/RISK180031","DOIUrl":"https://doi.org/10.2495/RISK180031","url":null,"abstract":"Old dams were usually constructed using simplified design criteria. Seismic action was not totally computed and included in the dams’ sizing procedure, mainly static forces were applied to the dam body and resistance to a seismic excitation of 0.1 g peak ground acceleration was verified. This can raise stability concerns because, according to its location, the dam could be subjected to stronger earthquakes. The Qaraoun concrete face rockfill dam (CFRD), the first Lebanese dam, built in 1964, is studied here to evaluate overall stability. The highest excitation predicted for the site is defined by seismic hazard assessment, the applied earthquake is the horizontal component of the Tabas earthquake that occurred in Iran in 1978, with a 7.4 magnitude and 0.8 g ground acceleration, since the specifications of such an earthquake match the required design solicitation. The simulation was performed using the finite element code Plaxis 2D; a numerical model is presented with all calibration steps and assumptions covering the lack of data regarding the materials’ properties. A non-linear behaviour was adopted for the rock fill; static and dynamic calculations were performed in order to obtain the permanent deformations, allowing for a judgement regarding the stability of the dam. A final settlement of one metre at the crest and a horizontal displacement of one metre are not threatening values, taking into consideration the level of the reservoir free board, which is 5 m below the dam crest.","PeriodicalId":21504,"journal":{"name":"Risk Analysis XI","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85642839","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Delhi, the capital of India, is experiencing a perennial influx of migrating population in highly congested, unplanned colonies having lack of basic civic and infrastructure amenities. The concentration of humans in numbers and activities in these areas has fostered new dimensions to fire hazards with enhanced risk to life and property. A greater proportion of poor quality housing, inadequate planning, monitoring and control in metropolitan cities lead to a greater number of fires and other urban disasters. Statistical tools coupled with geo-spatial techniques can be used to locate areas of high fire and life risk. Application of these techniques has the potential to help decision makers with proactive preventative measures and better resource allocations. This paper uses geo-spatial techniques to analyze the patterns of fire incidents in the South-West Division of Delhi from 2013–2016. Thematic maps depicting high, moderate and low level fire and life risk have been produced under a Geographical Information System (GIS) Environment for the area under study. The highest number of fire incidents was found to have occurred in low rise residential apartments and private dwellings. The occupants of residential colonies having low economic status were found to be more prone to injury and death during a fire incidence. In a domestic fire, Liquefied Petroleum Gas (LPG) was found to cause maximum injuries. The number of injuries due to fires was also observed to be higher during cold winter months, and fire incidents more frequent during 18:00 hrs–24:00 hrs. The number of fire deaths was found to be much higher between midnight and 06:00 hrs.
{"title":"IMPACT OF SPATIAL–TEMPORAL VARIATIONS ON FIRE VULNERABILITY: A CASE STUDY OF THE SOUTH-WEST DIVISION OF DELHI, INDIA","authors":"S. K. Tomar, A. Kaur, H. Dangi","doi":"10.2495/RISK180241","DOIUrl":"https://doi.org/10.2495/RISK180241","url":null,"abstract":"Delhi, the capital of India, is experiencing a perennial influx of migrating population in highly congested, unplanned colonies having lack of basic civic and infrastructure amenities. The concentration of humans in numbers and activities in these areas has fostered new dimensions to fire hazards with enhanced risk to life and property. A greater proportion of poor quality housing, inadequate planning, monitoring and control in metropolitan cities lead to a greater number of fires and other urban disasters. Statistical tools coupled with geo-spatial techniques can be used to locate areas of high fire and life risk. Application of these techniques has the potential to help decision makers with proactive preventative measures and better resource allocations. This paper uses geo-spatial techniques to analyze the patterns of fire incidents in the South-West Division of Delhi from 2013–2016. Thematic maps depicting high, moderate and low level fire and life risk have been produced under a Geographical Information System (GIS) Environment for the area under study. The highest number of fire incidents was found to have occurred in low rise residential apartments and private dwellings. The occupants of residential colonies having low economic status were found to be more prone to injury and death during a fire incidence. In a domestic fire, Liquefied Petroleum Gas (LPG) was found to cause maximum injuries. The number of injuries due to fires was also observed to be higher during cold winter months, and fire incidents more frequent during 18:00 hrs–24:00 hrs. The number of fire deaths was found to be much higher between midnight and 06:00 hrs.","PeriodicalId":21504,"journal":{"name":"Risk Analysis XI","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86346947","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The paper presents the results of a study on the economic risks affecting the competitiveness of power-generating companies. A methodical approach to the diagnosis of economic risks has been developed by the authors. The possibilities are estimated by using competitive advantages of various generating technologies on the basis of the method of decomposition of factors, which characterize economic risks. The process of development of power-generating companies involves the solution of complex problems related with the reliable power supply to consumers and the increase in efficiency of energy generation. The problem of increasing competitiveness requires the development of a special system for diagnosing the economic risks for power-generating companies. This implies forming a knowledge base necessary for the subsequent evaluation of the level of influence of economic risks on the competitiveness of energy sources. The approach proposed for diagnosing economic risks proposed is based on cluster and discriminant analyses. It allows determining the characteristics of energy-generating technologies that will give a high level of competitiveness. As a consequence, it becomes possible to study changes in the business environment and profitably take advantage of the potential advantages of the market. The evaluation of economic risks leads to assessing the level of their impact on the prospects of the presence of new energy-generating sources on the local energy market. It also permits analysis on the feasibility of exploiting their competitive advantages. The approach proposed is aimed at improving decision-making in conditions of uncertainty, minimizing economic risks and increasing the competitiveness.
{"title":"EVALUATION OF ECONOMIC RISKS FOR POWER-GENERATING COMPANIES","authors":"A. Domnikov, E. Antipova, L. Domnikova","doi":"10.2495/RISK180111","DOIUrl":"https://doi.org/10.2495/RISK180111","url":null,"abstract":"The paper presents the results of a study on the economic risks affecting the competitiveness of power-generating companies. A methodical approach to the diagnosis of economic risks has been developed by the authors. The possibilities are estimated by using competitive advantages of various generating technologies on the basis of the method of decomposition of factors, which characterize economic risks. The process of development of power-generating companies involves the solution of complex problems related with the reliable power supply to consumers and the increase in efficiency of energy generation. The problem of increasing competitiveness requires the development of a special system for diagnosing the economic risks for power-generating companies. This implies forming a knowledge base necessary for the subsequent evaluation of the level of influence of economic risks on the competitiveness of energy sources. The approach proposed for diagnosing economic risks proposed is based on cluster and discriminant analyses. It allows determining the characteristics of energy-generating technologies that will give a high level of competitiveness. As a consequence, it becomes possible to study changes in the business environment and profitably take advantage of the potential advantages of the market. The evaluation of economic risks leads to assessing the level of their impact on the prospects of the presence of new energy-generating sources on the local energy market. It also permits analysis on the feasibility of exploiting their competitive advantages. The approach proposed is aimed at improving decision-making in conditions of uncertainty, minimizing economic risks and increasing the competitiveness.","PeriodicalId":21504,"journal":{"name":"Risk Analysis XI","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80861391","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Subsea gas releases can have catastrophic impacts on human life, offshore assets, and the environment. As a result of major accidents that occurred recently, government regulations and company policies enforce a formal assessment of risks related to subsea gas releases. The main objective of subsea gas dispersion modelling is to predict the properties such as plume width, gas volume fraction and mean velocities at the sea surface in order to provide input data for risk models quantifying the topside risk exposure on offshore installations. This requires a comprehensive understanding of the dynamics of underwater releases of natural gas. This paper presents a comparison of different drag models applied for subsea gas dispersion modelling. ANSYS Fluent is used as the Computational Fluid Dynamics (CFD) modelling framework of the subsea gas plume hydrodynamics, while the changes of bubble’s density and size is included as an external user defined functions (UDFs) hooked to the Fluent’s main code structure. Four different drag models are compared, namely spherical drag law, modified spherical drag law, Xia’s drag law and Tomiyama’s drag law. The drag models are also incorporated into the main code structure as external UDFs. A combination of the two methods – Eulerian–Eulerian and Lagrangian – is used to model the bubbling behaviour of the subsea gas dispersion. The predicted results are validated against the experimental data presented by Engebretsen back in 1997. It is observed that the drag model in the CFD simulations seems to be a factor that could affect underwater plume physics. The predicted results show that the drag models including bubble shape show better agreement than the ones without including bubble shape in general.
{"title":"NUMERICAL COMPARISON OF DRAG MODELS APPLIED TO SUBSEA GAS DISPERSION","authors":"A. Kumara, Taewook Kim","doi":"10.2495/RISK180231","DOIUrl":"https://doi.org/10.2495/RISK180231","url":null,"abstract":"Subsea gas releases can have catastrophic impacts on human life, offshore assets, and the environment. As a result of major accidents that occurred recently, government regulations and company policies enforce a formal assessment of risks related to subsea gas releases. The main objective of subsea gas dispersion modelling is to predict the properties such as plume width, gas volume fraction and mean velocities at the sea surface in order to provide input data for risk models quantifying the topside risk exposure on offshore installations. This requires a comprehensive understanding of the dynamics of underwater releases of natural gas. This paper presents a comparison of different drag models applied for subsea gas dispersion modelling. ANSYS Fluent is used as the Computational Fluid Dynamics (CFD) modelling framework of the subsea gas plume hydrodynamics, while the changes of bubble’s density and size is included as an external user defined functions (UDFs) hooked to the Fluent’s main code structure. Four different drag models are compared, namely spherical drag law, modified spherical drag law, Xia’s drag law and Tomiyama’s drag law. The drag models are also incorporated into the main code structure as external UDFs. A combination of the two methods – Eulerian–Eulerian and Lagrangian – is used to model the bubbling behaviour of the subsea gas dispersion. The predicted results are validated against the experimental data presented by Engebretsen back in 1997. It is observed that the drag model in the CFD simulations seems to be a factor that could affect underwater plume physics. The predicted results show that the drag models including bubble shape show better agreement than the ones without including bubble shape in general.","PeriodicalId":21504,"journal":{"name":"Risk Analysis XI","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83777021","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In recent years, offshore operations have changed from a focus on anchor handling and rigging to more subsea installation and IMR (inspection, maintenance, repair). Situations where large and heavy modules are placed on the seabed by increasingly specialized and bigger boats creates the potential for major accidents. To uncover the safety challenges of this new development, 14 semi-structured in-depth interviews were conducted covering a broad scope of experience and skills from subsea work (ROV operators, crane operators, captains/first/second mates, oil service and oil company operators). All interviewees claimed that moving the offshore oil operations from surface to subsea leads to more demanding operations and more complex and risky work situations. According to the informants, these developments mean that cooperation and communication are essential since the number of actors increases substantially and the units grow larger. This seems to place increased demands in understanding both culture, language, tools, potential events, possible preventative measures (including training) and handling when critical events occur. Demanding situations occur when customers push on weather limits and costs and there are fewer people at work. Other situations viewed to be demanding are when something is hoisted through splash zones, and the moment when heavy constructions are placed on the seabed template. It has been shown that simulation training can improve safety and be an important preventive safety measure.
{"title":"WHAT ARE DEMANDING OPERATIONS IN SUBSEA WORK?","authors":"J. Håvold, L. Vederhus, Steinar Nistad","doi":"10.2495/RISK180211","DOIUrl":"https://doi.org/10.2495/RISK180211","url":null,"abstract":"In recent years, offshore operations have changed from a focus on anchor handling and rigging to more subsea installation and IMR (inspection, maintenance, repair). Situations where large and heavy modules are placed on the seabed by increasingly specialized and bigger boats creates the potential for major accidents. To uncover the safety challenges of this new development, 14 semi-structured in-depth interviews were conducted covering a broad scope of experience and skills from subsea work (ROV operators, crane operators, captains/first/second mates, oil service and oil company operators). All interviewees claimed that moving the offshore oil operations from surface to subsea leads to more demanding operations and more complex and risky work situations. According to the informants, these developments mean that cooperation and communication are essential since the number of actors increases substantially and the units grow larger. This seems to place increased demands in understanding both culture, language, tools, potential events, possible preventative measures (including training) and handling when critical events occur. Demanding situations occur when customers push on weather limits and costs and there are fewer people at work. Other situations viewed to be demanding are when something is hoisted through splash zones, and the moment when heavy constructions are placed on the seabed template. It has been shown that simulation training can improve safety and be an important preventive safety measure.","PeriodicalId":21504,"journal":{"name":"Risk Analysis XI","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82081819","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A hazard map is to represent the likelihood of future occurrences of hazardous events. Predicting the future, however, is far from easy and prone to uncertainty, misunderstanding and suspicion. This contribution presents a landslide-susceptibility prediction pattern that resembles a map but is a complex construction resulting from modelling and assumptions imposed on historical data. A mathematical model of spatial relationships, based on fuzzy sets, is applied to a spatial database that was constructed for landslide susceptibility studies in northern Italy. The resulting prediction pattern is dissected into its basic components to bring up the implied elements of spatial characterization, relevance of thematic input, assumptions in models and data, and visualization/interpretation of predicted scores. By the term prediction pattern we indicate the result of the classification of the study area into levels of relative susceptibility. Of particular relevance within the study area is the uncertainty associated with the scores, i.e., the ranks that classify the zones that are relatively more susceptible. Such a dissection is to lead to a confirmation of the credibility of the prediction pattern (hazard map?) based on the confidence gained by the comprehension of all elements integrated and assumptions made in its construction.
{"title":"HOW CREDIBLE IS MY HAZARD MAP? DISSECTING A PREDICTION PATTERN OF LANDSLIDE SUSCEPTIBILITY","authors":"A. Fabbri, C. Chung","doi":"10.2495/RISK180011","DOIUrl":"https://doi.org/10.2495/RISK180011","url":null,"abstract":"A hazard map is to represent the likelihood of future occurrences of hazardous events. Predicting the future, however, is far from easy and prone to uncertainty, misunderstanding and suspicion. This contribution presents a landslide-susceptibility prediction pattern that resembles a map but is a complex construction resulting from modelling and assumptions imposed on historical data. A mathematical model of spatial relationships, based on fuzzy sets, is applied to a spatial database that was constructed for landslide susceptibility studies in northern Italy. The resulting prediction pattern is dissected into its basic components to bring up the implied elements of spatial characterization, relevance of thematic input, assumptions in models and data, and visualization/interpretation of predicted scores. By the term prediction pattern we indicate the result of the classification of the study area into levels of relative susceptibility. Of particular relevance within the study area is the uncertainty associated with the scores, i.e., the ranks that classify the zones that are relatively more susceptible. Such a dissection is to lead to a confirmation of the credibility of the prediction pattern (hazard map?) based on the confidence gained by the comprehension of all elements integrated and assumptions made in its construction.","PeriodicalId":21504,"journal":{"name":"Risk Analysis XI","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76531771","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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