Volume 3: Structures, Safety, and Reliability最新文献

{"title":"Numerical Modelling of the Mooring Line Failure Induced Performance Changes of a Marine Fish Cage in Irregular Waves and Currents","authors":"H. Tang, Ray-Yeng Yang, Chai-Cheng Huang","doi":"10.1115/omae2019-95730","DOIUrl":"https://doi.org/10.1115/omae2019-95730","url":null,"abstract":"\u0000 This study aims to investigate the performance changes resulted from a mooring line failure of a marine fish cage exposed to irregular waves and current. A numerical model based on the lumped mass method and Morison equation was extended to simulate the mooring line failure scenario. In this study, the failed resulting changes were compared with its normal counterpart in both the time domain and the frequency domain. After one upstream anchor loss, the maximum tension on the remaining anchor has increased significantly, as well as the drift distance of the rearing part (net chamber, floating collar, and tube-sinker) of the fish cage. The resulting changes can also be seen in both the wave-frequency and the low-frequency region in the spectra, including mooring tensions and body motions.","PeriodicalId":314553,"journal":{"name":"Volume 3: Structures, Safety, and Reliability","volume":"215 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116999645","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":"Comparison of Temporal and Spatial Statistics of Nonlinear Waves","authors":"E. Bitner-Gregersen, O. Gramstad","doi":"10.1115/omae2019-95357","DOIUrl":"https://doi.org/10.1115/omae2019-95357","url":null,"abstract":"\u0000 In the past, it was most common to derive wave parameters and their statistics from time series of wave elevation. The duration of the wave records has been usually restricted to 20 or 30 minutes. Recently, increasing attention has started to be given to spatial wave data and wave statistics, particularly due to introduction in oceanography of stereo camera systems for collecting space–time ensemble of sea surface elevation. Using numerical linear, 2nd and 3rd order simulations this study compares temporal and spatial statistics of wave parameters. The 3rd order wave data are simulated by a numerical solver based on the Higher Order Spectral Method (HOSM) which includes the leading order nonlinear dynamical effects, accounting for the effect of modulational instability. The Pierson-Moskowitz and the JONSWAP spectrum with different gamma parameters are used in the analysis. Sea states with wave steepness where rogue waves were recorded in nature are considered. Consequences of using temporal contra spatial statistics are discussed in perspective of marine structures’ design. Functional dependency between wave parameters characterizing occurrence of rogue waves in unidirectional wave field is proposed.","PeriodicalId":314553,"journal":{"name":"Volume 3: Structures, Safety, and Reliability","volume":"61 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131770347","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":"Mechanical Modeling of the Polymeric Coating on a Subsea Pipeline","authors":"Ole Vestrum, M. Langseth, T. Børvik","doi":"10.1115/omae2019-95920","DOIUrl":"https://doi.org/10.1115/omae2019-95920","url":null,"abstract":"\u0000 Offshore pipelines may be exposed to a range of extreme loading situations during operation on the seabed such as impact by trawl gear or anchors. While not primarily being designed for it, thermal insulating polymeric coatings are experienced to provide beneficial contributions to the structural integrity of subsea pipeline designs. In recent editions, the prevailing standards and design guidelines are allowing for the inclusion of external coating products in the mechanical design evaluation. This secondary functionality of insulating coatings presents a great potential in terms of more optimized pipeline designs. However, due to the lack of reliable and versatile mechanical models, any beneficial effects from these complex polymeric insulating coatings are often omitted in simulations. This work presents a finite element based approach for assessing the mechanical response of polymeric coatings on offshore pipelines with different porous structures imaged using X-ray micro computed tomography. The modeling approach is also compared with experimental results.","PeriodicalId":314553,"journal":{"name":"Volume 3: Structures, Safety, and Reliability","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132082689","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":"Mode Selection for Offshore Platform Damage Identification Using CMSE Sensitivity","authors":"Mingqiang Xu, Yuchi Liu, Yufeng Jiang, Shuqing Wang","doi":"10.1115/omae2019-95550","DOIUrl":"https://doi.org/10.1115/omae2019-95550","url":null,"abstract":"\u0000 A sensitivity-based mode selection strategy for cross modal strain energy (CMSE) method is proposed to identify damage more effectively. The cross modal strain energy sensitivity is defined as the sensitivity index. For this purpose, the cross modal strain energy sensitivity to structural damage is deduced, and is used to select the preferable mode combinations that are sensitive to damage. By using the preferable mode combinations, the CMSE system is refined and the degree of ill-posedness of the CMSE system is reduced. A numerical study is conducted on an offshore platform structure to demonstrate the effectiveness of the proposed scheme. The performances of the CMSE method with and without using the mode selection strategy are compared in the presence of noise. Results show that: (1) the accuracy of damage localization is improved when only a few mode combinations are utilized; (2) On account of excluding substantial low-sensitivity mode combinations, the amount of computation is significantly reduced.","PeriodicalId":314553,"journal":{"name":"Volume 3: Structures, Safety, and Reliability","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115453727","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":"Comparison of the Environmental Contour Method and Response-Based Analysis Using Response Emulator for Estimating Extreme Ship Responses","authors":"E. Vanem, B. Guo","doi":"10.1115/omae2019-95098","DOIUrl":"https://doi.org/10.1115/omae2019-95098","url":null,"abstract":"\u0000 Environmental contours are often applied in probabilistic structural reliability analysis to identify extreme environ-mental conditions that may give rise to extreme loads and responses. They facilitate approximate long term analysis of critical structural responses in situations where computationally heavy and time-consuming response calculations makes full long-term analysis infeasible. The environmental contour method identifies extreme environmental conditions that are expected to give rise to extreme structural response of marine structures. The extreme responses can then be estimated by performing response calculations for environmental conditions along the contours.\u0000 Response-based analysis is an alternative, where extreme value analysis is performed on the actual response rather than on the environmental conditions. For complex structures, this is often not practical due to computationally heavy response calculations. However, by establishing statistical emulators of the response, using machine learning techniques, one may obtain long time-series of the structural response and use this to estimate extreme responses.\u0000 In this paper, the contour method will be compared to response-based estimation of extreme vertical bending moment for a tanker. A response emulator based on Gaussian processes regression with adaptive sampling has been established based on response calculations from a hydrodynamic model. Long time-series of sea-state parameters such as significant wave height and wave period are used to construct N-year environmental contours and the extreme N-year response is estimated from numerical calculations for identified sea states. At the same time, the response emulator is applied on the time series to provide long time-series of structural response, in this case vertical bending moment of a tanker. Extreme value analysis is then performed directly on the responses to estimate the N-year extreme response. The results from either method will then be compared, and it is possible to evaluate the accuracy of the environmental contour method in estimating the response.","PeriodicalId":314553,"journal":{"name":"Volume 3: Structures, Safety, and Reliability","volume":"34 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114109098","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":"Ultimate Compressive Strength of Eccentrically Loaded Stiffened Panels in Ship Structures: A Computational Study","authors":"K. Anyfantis","doi":"10.1115/omae2019-96708","DOIUrl":"https://doi.org/10.1115/omae2019-96708","url":null,"abstract":"\u0000 Ship scantlings are obtained through a linear elastic design framework. In relatively long ships, the mid-ship’s ultimate strength capacity must be checked whether it is below a certain level (given factor of safety). Smith’s method is based on an incremental-iterative approach where constitutive equations of idealized representative components are used to model the different involved buckling modes. The literature body neglects the local bending effect applied at the stiffener with the attached plating (considered here as the representative element). This work studies the eccentrically loaded representative element from its compressive resistance point of view. The eccentricity sources from the linear varying strain field produced as a result of pure bending of the ship’s mid-section and is relative to the location of the stiffened panel from the ship’s section Neutral Axis. Therefore, the representative element has been considered as a part of the ship’s structure and the inherent eccentricity is analytically calculated in terms of geometric and material properties. A computational study has been further performed in a non-linear finite element environment in order to figure out the effect of the eccentricity level to the ultimate compressive strength of the representative element. Geometric distortions have been also included in the FE models in order to allow for accurate strength calculations. Numerical results have shown that, in realistic proportions of large ships, the further the representative element is located from the mid-ship’s NA the smaller is the deviation from pure compressive load strength analysis results. However, for the element laying near the ship’s NA, idealized models overestimate the strength by 10% compared to realistic analytical / numerical results for the typical scantling case considered.","PeriodicalId":314553,"journal":{"name":"Volume 3: Structures, Safety, and Reliability","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134465497","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":"Dynamic Response of Metallic Y-Frame Core Sandwich Panels Subjected to Air Blast Loading: Numerical Investigation","authors":"Ting-yu Liu, Yuansheng Cheng, Jun Liu, Ganchao Chen, Changhai Chen, Pan Zhang","doi":"10.1115/omae2019-96628","DOIUrl":"https://doi.org/10.1115/omae2019-96628","url":null,"abstract":"\u0000 In this paper, the dynamic response of metallic Y-frame core sandwich plates subjected to air blast loading was investigated by employing the LS-DYNA software. The blast wave was generated by the directly detonation of TNT explosives. The deformation/failure modes and associated structural response were identified and analyzed in detail. Main attention was paid to explore the effects of face sheet thicknesses and core web thickness on the deformation response of Y-frame core sandwich plates. A comparison on the blast performance were drawn among the Y-frame core sandwich panel, corrugated core sandwich panel and solid plate in equal areal mass. Numerical results revealed that the Y-frame core sandwich panel experienced indent deformation in the front face, strut buckling in the core and large bending deformation in the back face under the stand-off distance of 100 mm. Increasing the face sheets and core web thicknesses could improve the blast performance of Y-frame core sandwich panels. The deflections of face sheets were sensitive to the variation of front face sheet and core thicknesses. Moreover, Y-frame sandwich panel has comparable anti-blast capacity with the corrugated counterparts and exhibits superior blast resistance than the solid plate.","PeriodicalId":314553,"journal":{"name":"Volume 3: Structures, Safety, and Reliability","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129722382","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":"Risk Assessment in Offshore Salt Caverns to Store CO2","authors":"M. A. Pestana, C. Morais, Á. M. Costa, C. Brandão, M. Martins","doi":"10.1115/omae2019-96250","DOIUrl":"https://doi.org/10.1115/omae2019-96250","url":null,"abstract":"\u0000 Although factual experience of developing offshore salt cavern to CO2 disposal in ultra-deep water is unprecedent, the theme has been gaining relevant attention in Brazil, fueled by the challenges imposed by oil production on the Pre-Salt reservoirs. It is true that some authors have conducted researches related to CO2 disposal on onshore salt caverns, but most of the works regarding salt cavern are related to onshore constructions that are used as methane store to supplement gas consumption during the peak energy demands that historically occurs during the winter season in the North hemisphere. This paper aims to contribute for CO2 disposal research, describing the results obtained from the application of a Preliminary Risk Analysis (PRA) during the conceptual engineering phase of an offshore salt cavern to store CO2 in Brazilian Pre-Salt.","PeriodicalId":314553,"journal":{"name":"Volume 3: Structures, Safety, and Reliability","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130964606","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":"Predicting Extreme Waves From Wave Spectral Properties Using Machine Learning","authors":"O. Gramstad, E. Bitner-Gregersen","doi":"10.1115/omae2019-96061","DOIUrl":"https://doi.org/10.1115/omae2019-96061","url":null,"abstract":"\u0000 An important question in the context of rogue waves is whether the statistical properties of individual waves, and in particular the probability of extreme and rogue waves, can be linked to the properties of the underlying wave spectrum of the relevant sea state.\u0000 It has been suggested that a narrow wave spectrum (in frequency or direction) combined with a large wave steepness may lead to increased occurrence of extreme waves. Parameters based on the ratio of the wave steepness to the spectral band-widths have therefore been suggested as indicators of increased probability of extreme waves. However, for realistic ocean conditions the success of such parameters seems to be questionable.\u0000 In this paper, we investigate relations between short-time wave statistics and wave spectral properties by using machine learning methods that can take a much wider range of spectral properties, or even the entire directional wave spectrum, into account. Numerical simulations with a nonlinear wave model that provides phase-resolved wave information are combined with wave spectra from a spectral wave model. Machine learning methods are then employed to investigate how well the wave statistics can be predicted from knowledge about the wave spectrum.\u0000 The results are discussed in the context of existing parameters suggested as indicators of rogue waves, as well as with respect to potential warning against sea states in which extreme waves are expected to occur, based on wave-forecast from spectral wave models.","PeriodicalId":314553,"journal":{"name":"Volume 3: Structures, Safety, and Reliability","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117084685","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":"Impacts of Condensate Storage on the Hull Structure Design of Semi Submersible Platform","authors":"Jiaguo Feng, Yi Yu, Da Li, Bin Xie, Wenhui Xie, Haishan Zhu, Min Wu","doi":"10.1115/omae2019-96601","DOIUrl":"https://doi.org/10.1115/omae2019-96601","url":null,"abstract":"\u0000 In order to develop the gas field in South China Sea, a deep-draft semi-submersible platform with 20000 m3 condensate storage tanks was selected. There is little industrial experience for semi-submersible platform with the condensate producing and storage tanks. This paper presents the impacts caused by the condensate producing and storage on the hull structure design in FEED phase. The design life is 30 years without returning to drydock for repair or maintenance.\u0000 The main unique features are illustrated as follows. Firstly, the double-wall voids (cofferdams) of 1.8 meters width were designen to prevent condensate leakage in the column around the condensate tanks. The double-wall bulkheads were connected by flats with manholes for maintenance access. this is different from conventional semi-submersible platform. Secondly, the non-watertight bulkheads in the middle of the condensate tank were needed to meet the efficient strength requirements for structural design. The upper and lower 2m height gaps on the bulkhead are convenient for the flowing of bottom condensate and top gas in condensate tank respectively. It is proven that the optimized design of continuous non-watertight bulkhead for the condensate tank is feasible, safe and reliable based on the global strength and fatigue analysis. Thirdly, The additional corrosion margin of 2mm was added to the boundary of frequently ballast and de-ballast tanks in the nodes and columns, and to the bottom plate and the side shell of 2m height from the bottom of condensate tanks considering the SEMI design life of 30 years. Fourth, the pressure head for condensate tank scantling design was increased by 10 m per condensate tank vent head location on topside. Fifth, there are some indirect effects due to the condensate storage, such as the increase of displacement and the load on the SEMI. Therefore, the hull structure needs to be reinforced, especially on the key connections, such as the column and pontoon connection, the deck and hull connection. It is recommended to pay attention to these critical locations with detailed local analyses.","PeriodicalId":314553,"journal":{"name":"Volume 3: Structures, Safety, and Reliability","volume":"148 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121537163","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}