Day 3 Wed, August 18, 2021最新文献

{"title":"Fracture Mechanics Assessment of Cracks in Areas of Large Scale Plasticity in Subsea HPHT Equipment","authors":"M. Kulkarni, Carlos López, Daniel J Kluk, J. Chappell","doi":"10.4043/30999-ms","DOIUrl":"https://doi.org/10.4043/30999-ms","url":null,"abstract":"\u0000 Subsea HPHT components may be evaluated utilizing a fracture mechanics-based approach as per guidelines in API RP 17TR8 and ASME Section VIII Division 3. Typically, the assessment is performed based on methods described in API 579-1/ASME FFS-1 and BS7910. The analysis is performed to determine critical flaw sizes and estimate the fatigue life of a growing crack as a means of establishing inspection intervals for the equipment. In most cases, the assessment is based on a linear elastic fracture mechanics approach. The effect of plasticity is generally included via the use of a failure assessment diagram (FAD); however, even with this approach the effect of plastic strain around the crack is not explicitly considered. The assessment standards do not provide clear guidance for cases involving a crack which is located within a region of large-scale plastic strain. For these cases, API 579, Annex 9G.5 recommends utilizing a driving force method whereby the J-integral is directly evaluated from an elastic-plastic finite element model.\u0000 This paper presents such an approach. A simplified representative geometry is considered for this study. A region of a stress concentration, such as is typically encountered near an internal radius is considered. Such a region can potentially show localized plasticity. J-integral is calculated by explicitly modeling a series of cracks of increasing depth through this zone of plasticity and the results are compared to the different methodologies described in API 579-1/ASME FFS-1 and BS7910. Cracks are modeled both completely and partially enveloped within the plastic zone.\u0000 Results are summarized and compared, highlighting the key differences between different analysis approaches with the aim of identifying the most conservative assessment method for different crack sizes. Additionally, the effect of large-scale plasticity on the crack driving force is determined relative to similar conditions without plasticity. The results indicate that for cracks lying within the regions of localized plasticity, using an API579 Level 2 approach coupled with extracting elastic-plastic through wall stresses from an uncracked geometry may result in significant under prediction of the driving force. Conversely, extracting linear elastic stresses from an uncracked geometry may significantly over predict the driving force and may prove too conservative for determining acceptable crack sizes.\u0000 This paper presents a comprehensive comparison of different analysis approaches used for evaluating cracks in subsea equipment. The results indicate that, for HPHT equipment with increased safety implications, a detailed elastic plastic fracture mechanics evaluation of the cracked geometry should be performed for cases in which localized plasticity is expected to occur.","PeriodicalId":11184,"journal":{"name":"Day 3 Wed, August 18, 2021","volume":"56 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81048570","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}

{"title":"Wandoo B: Application of Advance Reinforced Concrete Assessment for Life Extension for Non-Jacket Structures","authors":"R. Sheppard, C. O’Brien, Y. Moslehy, R. Roberts","doi":"10.4043/31250-ms","DOIUrl":"https://doi.org/10.4043/31250-ms","url":null,"abstract":"\u0000 Wandoo B is a concrete Gravity Base Structure (GBS) and is the main production facility for the Wandoo field offshore NW Australia. It was installed in 1997 with a design life of 20 years. The structural assessments discussed in this paper are part of a comprehensive life extension project encompassing wells, subsea systems, marine and safety systems, topsides facilities and structures to demonstrate fitness for service through the end of field life (EOFL).\u0000 The challenge was to demonstrate compliance efficiently and effectively for a large structure with a range of materials (steel, reinforced concrete (RC)) and operations supported (oil storage, drilling, production) under increased loading criteria compared to the original design. There is comprehensive industry guidance for assessing existing steel jacket structures, but far less for a concrete GBS such as Wandoo B. Demonstrating compliance required a combination of computer model results, project-specific tools to check reinforced concrete sections, and engineering judgement to define how much damage constitutes failure.\u0000 A number of global and local structural models were developed to assess the linear and nonlinear performance of the reinforced concrete and steel structure. A phased approach was employed using basic, conservative approaches in initial phases to demonstrate code compliance, and progressing to more advanced, less conservative approaches for those components under higher stress.\u0000 Developing models that more accurately simulate the behavior of the different structural components and materials was a large part of the project scope, particularly for the nonlinear behavior of the reinforced concrete and the interface connections between the steel and reinforced concrete structures. It was inefficient to develop a detailed steel and reinforced concrete solid model of the large GBS shafts and base, so an equivalent shell model was developed and tested to determine the global behavior and onset of damage. This equivalent model aimed to predict behavior accurately for metocean and seismic loads under material tension and compression. Local detailed models were then developed including a constitutive model of reinforced concrete and used to define the extent of the damage and predict where failure would occur.","PeriodicalId":11184,"journal":{"name":"Day 3 Wed, August 18, 2021","volume":"19 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88947714","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}

{"title":"Energetics and Kinematics of Inertial Oscillations in the Central Northern GOM","authors":"L. Ivanov, R. Ramos, Drew Gustafson","doi":"10.4043/31020-ms","DOIUrl":"https://doi.org/10.4043/31020-ms","url":null,"abstract":"\u0000 Understanding the physics of generation, propagation, and dissipation of inertial currents is important from a variety of aspects. For the Gulf of Mexico, one such aspect is that these oscillations represent an uncertainty in the measurements and forecasting of the longer-period currents, such as those due to the Loop Current (LC) and meso-scale eddies. The Industry has a practice of applying an ‘uplift’ to estimates of current velocity to account for the effect of tidal and inertial currents in cases when observations or model estimates do not resolve the high-frequency current variability. The value of the ‘uplift’ is assumed to be proportional to the intensity of the low-frequency flow. Our analysis aims at testing whether this assumption is valid by providing a detailed description of the space-time variability, including seasonal changes, of inertial oscillations in the central northern Gulf of Mexico. From the analysis of long-term current profile observations and drifter data we found that, on average, near-inertial oscillations have higher amplitudes outside of the areas of strong low-frequency currents associated with a Loop Current Eddy (LCE). Within the upper 200m of the water column, periods characterized by the downward energy propagation dominate. In the layer below 200m, near-inertial waves propagate upward and downward, and the wave trains cannot be traced to a single source of energy. This suggests near-inertial waves within the main part of the water column are of ‘global’ rather than of ‘local’ origin. For most near-inertial wave generation events through wind forcing, the downward energy propagation could not be traced for any extended period of time and no deeper than approximately 200-m depth. The rate of downward energy propagation in the upper pycnocline is on the order of 10-12 m/day. For the near-inertial currents, the first two Empirical Orthogonal Functions (EOF) contribute only 40% into the total current variability for the period of LCE presence and 52% for the period of benign current conditions. The mode shapes vary within a wide range that, most likely, reflects a random distribution of mode shapes that depend on the lateral geometry of the forcing, mixed layer depth, and stratification.","PeriodicalId":11184,"journal":{"name":"Day 3 Wed, August 18, 2021","volume":"31 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87109670","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}

{"title":"Autonomous Subsea Field Development - Value Proposition, Technology Needs and Gaps for Future Advancement","authors":"Giorgio Arcangeletti, M. Mattioli, Mark Ausborn, D. Matskevitch, Amedeo Marcotulli","doi":"10.4043/31151-ms","DOIUrl":"https://doi.org/10.4043/31151-ms","url":null,"abstract":"\u0000 With increasing demand of subsea processing and surveillance goals Best-in-Class Operators are developing advanced subsea instrumentation and controls to challenge in the next decade: i) a cost-effective way to inspect and repair subsea complex facilities and ii) to reduce the downtime, possibly increase the production performance while preserving the integrity and maintenance of the assets.\u0000 The so called \"Autonomous Subsea Field Development\" is a study triggered by an ExxonMobil URC (Upstream Research Company) initiative aimed to explore possible improvements and re-designs of subsea equipment considering the advancing capabilities of ROVs and new generation of Subsea Drones, and driven by the following questions:\u0000 with the advancements in AUVs and ROVs, can subsea equipment be re-designed to take full advantage of the new capabilities? Can this re-design improve from different perspectives (Availability, Costs, Operations, etc.) a subsea field development?\u0000 A dedicated study was conducted by SAIPEM to identify the value proposition, technology needs and gaps for future advancement by leveraging on the technological \"building blocks\" that could be integrated in a subsea field development scheme and on a field operational procedure.\u0000 Within the study, seven different cases, distinguished by their status of advancement (from Brown to Green Fields) and by the level of penetration of Subsea Drones in the architecture, have been analyzed.\u0000 A conceptual engineering process, based on the tenets of value engineering was conducted in a holistic fashion covering the full field development facilities during the life cycle in order to steer the conceptual engineering choices that could maximize the project value.\u0000 Using a systemic Value Engineering approach based on the NPV equation, the study identified the main technological and economic impacts coming from the adoption of Subsea Drones on a current and future Digital Subsea Field exploring the following pillars: i) CAPEX, ii) OPEX, iii) AVAILABILITY, and iv) RISK.\u0000 In the sequence of six cases investigated, it has been identified how these incoming \"subsea capabilities\" will be gradually implemented into redesigned subsea architecture and serviced in view of a new Life of Field concept.","PeriodicalId":11184,"journal":{"name":"Day 3 Wed, August 18, 2021","volume":"55 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87322195","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}

{"title":"TRACS JIP – TTR Life Extension Process","authors":"Dhyanjyoti Deka, M. Campbell, V. Patil, M. Ge, Steve Wong, Timothy A. Frame","doi":"10.4043/31060-ms","DOIUrl":"https://doi.org/10.4043/31060-ms","url":null,"abstract":"\u0000 The Tensioned Riser Assessment for Continued Service (TRACS) JIP develops a structured life extension process for TTR systems including single casing, dual casing, buoyancy can supported and tensioner supported TTRs. The JIP bridges regulatory and API frameworks and achieves industry consensus on analysis, inspections, and documentation.\u0000 The life extension process developed in this JIP consists of detailed roadmaps that guide the operator through the different assessment steps starting from initial data gathering through to the development of the forward-looking IMP. The JIP life extension process is based on a threat assessment philosophy which ensures identification and assessment of all possible threats to the integrity of the TTR in its extended life.\u0000 The JIP process is validated against three real life TTR systems that are nearing the end of their design lives. Potential threats to the integrity of these TTRs during the projected continued service beyond the design life are identified and specific inspection and analysis recommendations to safely manage or mitigate these threats are made.\u0000 The JIP also provides TTR life extension analysis guidance while considering the opportunities to reduce conservatism compared to new designs. Inspection of TTRs is challenging due to accessibility issues and the pipe in pipe construction. Several subsea NDE inspection tools are surveyed in this JIP and their applicability to TTRs is discussed.","PeriodicalId":11184,"journal":{"name":"Day 3 Wed, August 18, 2021","volume":"33 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86916392","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}

{"title":"Protective Barrier Wall Response to Sequential Blast and Fire Events","authors":"Hunter Smith","doi":"10.4043/31115-ms","DOIUrl":"https://doi.org/10.4043/31115-ms","url":null,"abstract":"\u0000 Blast and fire-resistant barrier walls are often required on offshore platforms to protect from accidental events. A wall structure designed for a probabilistic explosion event typically relies on inelastic response and plastic deformation to maintain a lightweight, efficient design. Design guides for such structures do not explicitly address how to account for the effects of interaction of blast and fire loading on structural performance and design acceptance criteria. If a wall assembly is required to provide rated fire and gas protection after an explosion event, it is generally assumed that structural integrity is maintained due to temperature increase limits (140°C) from the H-60/120 rated fire protection on the wall. This paper investigates the validity of this assumption for a typical offshore barrier wall designed to undergo permanent deformation during an initial blast event.\u0000 The study was performed utilizing non-linear dynamic finite element analysis (FEA). FEA allows for design iteration, structural assessment, and validation against extreme load scenarios when testing of full-scale assembly may not be feasible. A typical wall structure was first analyzed for blast loading by non-linear dynamic structural analysis. Thermal loading from a subsequent hydrocarbon fire was then applied to observe the structural response in the post-blast damaged condition. Based on the rated temperature range, the resulting thermal expansion in the wall panels induces large stresses at the interface between wall panels and supporting steel. Non-linear FEA confirmed that yielding occurs which may increase existing plastic strains beyond design limits at locations of high stress concentration. Therefore, it is prudent to consider thermal performance in the design process, especially regarding connections and penetrations.","PeriodicalId":11184,"journal":{"name":"Day 3 Wed, August 18, 2021","volume":"11 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87446407","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}

{"title":"Reducing THI Injection and Gas Hydrate Agglomeration by Under-Inhibition of Crude Oil Systems","authors":"J. Delgado-Linares, Ahmad A. A. Majid, L. Zerpa, C. Koh","doi":"10.4043/31161-ms","DOIUrl":"https://doi.org/10.4043/31161-ms","url":null,"abstract":"\u0000 Gas hydrates constitute a serious flow assurance problem. Over the last decades, industry has faced this problem by using avoidance methods (e.g. injection of thermodynamic hydrate inhibitors) and management strategies (e.g. addition of hydrate anti-agglomerants). In the former, hydrates are completely avoided by shifting the hydrate boundary towards higher pressure and lower temperatures; in the latter, hydrates are allowed to form but their tendency to agglomerate is reduced. It should be noted that some crude oils are naturally able to avoid hydrate agglomeration, this non-plugging tendency may originate from the surfactant-like behavior of fractions like asphaltenes and acids. Recent works have shown that the natural non-plugging potential of certain oils can be affected by the addition of polar molecules like alcohols.\u0000 There is another strategy for managing hydrate that consist of the addition of THIs at a concentration lower that the one required to full hydrate inhibition. In this case, hydrates are under-inhibited. Studies carried out on hydrate agglomerating systems have shown that under-inhibition might prevent hydrate agglomeration only in a specific range of THI concentrations and sub-cooling; however, work on non-plugging oils is scarce. In this paper, the hydrate agglomeration of two crude oils under-inhibited with methanol and MEG was evaluated through a visual rocking cell apparatus and a high-pressure rheometer. Results showed that THIs and the crude oil's natural surfactants were capable of acting synergistically in reducing hydrate agglomeration and improving the system flowability.","PeriodicalId":11184,"journal":{"name":"Day 3 Wed, August 18, 2021","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83905812","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}

{"title":"Net Zero Facilities – A Tenet for Survival or a Pipedream","authors":"Richard F. Dyson, J. Varney, Vaseem Khan, Christopher Dartnell","doi":"10.4043/31098-ms","DOIUrl":"https://doi.org/10.4043/31098-ms","url":null,"abstract":"\u0000 To meet global climate targets, it is critical that the oil and gas industry address greenhouse gas (GHG) emissions attributable to its operations. According to the IEA, 15% of global energy-related GHG emissions arise from the process of hydrocarbon extraction and distribution. Production facilities built today may operate for 20-30 years, by which time industries, governments and countries have committed to significant reductions in emissions. If facilities are not designed with carbon neutrality in mind, there is a risk that carbon pricing may cause projects to become uneconomic before their planned end-of-life - an expensive folly. To meet GHG emission targets and de-risk projects it is essential that operators design and construct facilities with carbon neutrality in mind. This will future-proof their operations, ensuring that operators are active participants in a carbon neutral future. In fact, this is a tenet for survival in a world with pressure to decarbonise from shareholders, financial institutions, and society itself. This paper presents a pathway to the carbon neutral upstream facility. A methodology to achieve net-zero emissions for an offshore compression platform is proposed.\u0000 The project team used a Decision Quality framework to identify methods for achieving carbon neutrality, including:\u0000 Power import and electrification Renewable micro-grids Integration with hydrogen networks Reduction of fugitive emissions Flare system removal Facility demanning and access method Engineered offsetting methods (excluding nature-based offsetting) Digital Transformation of design and operations - remote operation and monitoring.\u0000 Design concepts were created to test carbon neutral facilities feasibility. Expertise gained from demanning projects, along with specialist Electrical & Instrumentation experience were used, to perform a techno-economic assessment. Class 5 CAPEX and OPEX estimates were prepared and compared against a Reference Case \"traditional\" facility design. Traditional approaches to facility design were challenged at every level and an optimal, carbon neutral design was identified based on the above assessments integrating the latest techniques and technology. The study team determined the facilities lifecycle cost, identifying breakeven carbon pricing required to ensure cost-competitiveness.\u0000 This paper demonstrates what is achievable with current technology, and opportunities for further technology development. Breakeven carbon pricing for carbon neutral facilities is presented within a range of economic scenarios. A hierarchy of technologies show those which have the biggest impact per dollar spent. This will allow operators to make informed decisions on areas that present the biggest targets for emissions reduction. The methodology can be adapted to any geographical region, considering local infrastructure and carbon pricing.\u0000 The approach presented can be applied across many industries. Long lifespan, capital intensive proje","PeriodicalId":11184,"journal":{"name":"Day 3 Wed, August 18, 2021","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90193317","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}

{"title":"First Use of ROV Remote Operations from Shore in the Gulf of Mexico","authors":"Simao Silva, Blake Terrell, Mark Philip, Nicholas Rouge, Diogenes Angelidis, Julio Sosa, R. Collins, Zain Rauf","doi":"10.4043/31019-ms","DOIUrl":"https://doi.org/10.4043/31019-ms","url":null,"abstract":"\u0000 Oil and gas companies across the spectrum are moving toward digitalization. Leveraging technology to access real-time data has allowed companies to streamline activities and gain operational efficiencies while at the same time improving worker safety by reducing the number of personnel required offshore. This evolution optimizes operations by enabling better decision-making by subject matter experts (SMEs) located around the world working as one interconnected team. Functions once performed exclusively by offshore personnel are being carried out today by onshore workers via remote technology. By capitalizing on the ability to communicate offshore via high-speed internet, it is now possible to carry out ROV operations using a team that includes onshore based personnel.\u0000 A recent project illustrates how ROV activities controlled from an onshore remote operations center in Louisiana were carried out successfully on a production Tension Leg Platform (TLP) in the Gulf of Mexico (GoM).\u0000 The technology used onboard the TLP is not new; operators have been remotely managing a range of functions on offshore assets for years. However, the project does apply this proven approach to ROV piloting operations for the first time commercially in the GoM.\u0000 Transferring ROV control from the offshore platform to a facility onshore is possible using a communication link that connect real-time data from the offshore asset to the onshore remote operations center (OROC). The two-way communications link provides a redundant system in which controls can be executed either from the offshore platform or from the remote operations center, allowing specialized roles that historically have been executed offshore, including that of the ROV pilot, subsea engineer, and company representative directing the work, to be transferred to a land-based team. The increase in data required from the offshore asset for the GoM project was managed via a dedicated link that provided data transfer at a minimum speed of 3 Mbps upload/download with a fail-safe system that automatically default control to the offshore ROV team in case of any failures in the communication link.\u0000 Remotely piloting an ROV from shore and coordinating with an offshore crew not only delivered a reduction in HSE exposure but reduced overall personnel costs on the asset by more than 30% for 24 hours of operations. This approach to ROV operations has the potential to reduce costs by reducing the number of workers required offshore even further if additional staff associated exclusively with the project subsea work scope is directed to work remotely from shore.","PeriodicalId":11184,"journal":{"name":"Day 3 Wed, August 18, 2021","volume":"381 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80689798","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}

{"title":"Advances in Offshore Structural Analysis Using Response-Based Time-Domain Approach","authors":"J. Kyoung, Sagar Samaria, J. O’Donnell, S. Tallavajhula","doi":"10.4043/31280-ms","DOIUrl":"https://doi.org/10.4043/31280-ms","url":null,"abstract":"\u0000 Demand for life extension assessments of floating offshore platforms continues to grow worldwide. Conventional structural analysis methods have limited ability to accurately capture non-linear environmental loading, non-linear loading by the mooring and riser systems, and resulting higher order hull responses. The uncertainties are typically managed by the factors of safety applied in the structural analysis. Time domain structural analyses have long promised to improve analysis accuracy and reduce these uncertainties. This paper describes a comprehensive and practical time domain structural analysis methodology applied to a deep-water semi-submersible-type floating platform including results for structural strength and fatigue. In addition, the time domain structural analysis was extended for use in fracture mechanics and the assessment of notional weld flaws to facilitate specification of impactful non-destructive examination (NDE).\u0000 Present time domain structural analysis methodology employs a response-based finite element analysis (FEA) conducted in the time domain. All external environmental loads and inertial forces are converted to a response-based stress-time history. Previously, conventional time domain structural analysis involves massive computation resources to resolve solutions at every time interval. Present methodology significantly improves computational efficiency to be practical in real-world problems. The improvement is achieved by decomposing the structural response into a set of multiple load components selected on the bases of function for hull motion response and environmental loadings. Structural response in time domain is directly obtained by synthesizing the load components. An actual time domain structural response is captured effectively and efficiently to simulate the strength and fatigue criterion for the structure with consistent environmental loads and hull responses.\u0000 Utilizing the level of detail provided by the time domain structural analysis methodology, a fracture mechanics evaluation of notional initial flaws (engineering criticality assessments – ECAs) can be conducted providing meaningful technical basis for in-service NDE and life extension assessments. The procedures for fatigue crack growth and fracture documented in BS 7910 were employed to derive the smallest initial flaws (critical initial flaws) that may result in structural failure during a facility's lifetime.\u0000 A comparison indicates that conventional structural analysis methods provide conservative results for both structural strength and fatigue damage calculations resulting from the linear assumption of environmental loads and hull responses. Present time domain structural analysis methodology provides an innovative, cutting-edge approach providing accuracy and fewer uncertainties, which can be pragmatically used during a typical project.","PeriodicalId":11184,"journal":{"name":"Day 3 Wed, August 18, 2021","volume":"56 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91298486","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}