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

{"title":"Nonlinear Fourier Analysis Algorithm and Models for Water Waves in Terms of Surface Elevation, Amplitude Modulations","authors":"A. Osborne","doi":"10.1115/omae2019-95546","DOIUrl":"https://doi.org/10.1115/omae2019-95546","url":null,"abstract":"\u0000 This paper addresses two issues with regard to nonlinear ocean waves. (1) The first issue relates to the often-confused differences between the coordinates used for the measurement and characterization of ocean surface waves: The surface elevation and the complex modulation of a wave field. (2) The second issue relates to the very different kinds of physical wave behavior that occur in shallow and deep water. Both issues come from the known, very different behaviors of deep and shallow water waves. In shallow water one often uses the Korteweg-deVries that describes the wave surface elevation in terms of cnoidal waves and solitons. In deep water one uses the nonlinear Schrödinger equation whose solutions correspond to the complex envelope of a wave field that has Stokes wave and breather solutions. Here I make clear the relationships between the two ways of characterizing surface waves. Furthermore, and more importantly, I address the issues of matching the two types of wave behavior as the wave motion passes from deep to shallow water, or vice versa. For wave measurements we normally obtain the surface elevation with a wave staff, resistance gauge or pressure recorder for getting time series. Remote sensing applications relate to the use of lidar, radar or synthetic aperture radar for obtaining space series. The two types of wave behavior can therefore crucially depend on where the instrument is placed on the “ground track” or “field” over which the lidar or radar measurements are made. Thus the matching problem from deep to shallow water is not only important for wave measurements, but also for wave modeling. Modern wave models [Osborne, 2010, 2018, 2019a, 2019b] that maintain the coherent structures of wave dynamics (solitons, Stokes waves, breathers, superbreathers, vortices, etc.) must naturally pass from deep to shallow water where the nature of the nonlinear physics, and the form of the coherent structures, change. I address these issues and more herein. This paper is directed towards the development of methods for the real time measurement of waves by shipboard radar and for wave measurements by airplane and helicopter using lidar and synthetic aperture radar. Wave modeling efforts are also underway.","PeriodicalId":314553,"journal":{"name":"Volume 3: Structures, Safety, and Reliability","volume":"20 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":"114295134","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":"Experimental Study on Ultimate Strength of Thin-Walled Square Tube Under Axial Compression","authors":"Han-wei Zhou, Ling Zhu, Shengming Zhang, T. X. Yu","doi":"10.1115/omae2019-96134","DOIUrl":"https://doi.org/10.1115/omae2019-96134","url":null,"abstract":"\u0000 There are many welded thin-walled square tube structures in ship structures. At present, researchers are mainly involved in axial compressive ultimate strength of square tubes with large aspect ratios. However, the study of square tubes with small aspect ratios on ultimate strength capacity have seldom been conducted. In order to study the ultimate strength capacity of thin-walled square tubes with small aspect ratio under axial compression, three welded thin-walled square tubes with different slenderness ratios were manufactured and studied in this paper. The ultimate strength of those models under axial compression were obtained experimentally. The experimental results were compared with numerical results performed by ABAQUS. The influence of slenderness ratios on the axial compressive ultimate strength of thin-walled square tubes is analyzed, and a feasible modelling of finite element method is proposed.","PeriodicalId":314553,"journal":{"name":"Volume 3: Structures, Safety, and Reliability","volume":"81 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":"133386763","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":"Towards Implementing Condition-Based Maintenance (CBM) Policy for Offshore Blowout Preventer (BOP) System","authors":"T. Elusakin, M. Shafiee, T. Adedipe","doi":"10.1115/omae2019-95539","DOIUrl":"https://doi.org/10.1115/omae2019-95539","url":null,"abstract":"\u0000 With the steadily growing demand for energy in the world, oil and gas companies are finding themselves facing increasing capital and operating costs. To ensure the economic viability of investments and improve the safety of operations, oil and gas companies are promoting their asset integrity management (AIM) systems. In the past, the oil and gas industry adopted reactive maintenance regimes, which involved recertification, testing and repair of faulty equipment while trying to achieve minimum downtime. As technology becomes more affordable, operators have been able to carry out improved fault diagnosis, prognosis and maintenance optimisation. As a result of this, condition-based maintenance (CBM) is being adopted more and more as the preeminent maintenance regime for oil and gas equipment. The blowout preventer (BOP) is one of the most expensive and safety critical drilling equipment in the oil and gas industry. However, there have been very few studies and best practices about how to develop a CBM policy and what specific monitoring techniques and devices will be required to implement it for the BOP system. This paper proposes a V-model based architecture for designing a CBM policy in BOP systems. As a result of the model proposed, gaps in implementation are identified and all the hardware, software and training requirements for implementing the CBM solution in BOP systems will be outlined in detail. Our proposed CBM framework will help BOP operators and maintenance personnel make cost savings through less repairs and replacements and minimal downtime.","PeriodicalId":314553,"journal":{"name":"Volume 3: Structures, Safety, and Reliability","volume":"205 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":"131438329","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":"Quasi-Static and Dynamic Compressive Behaviors of Closed-Cell Stochastic Foams Based on Voronoi Model","authors":"Jianyong Chen, Jun Liu, Yuansheng Cheng, Pan Zhang","doi":"10.1115/omae2019-95924","DOIUrl":"https://doi.org/10.1115/omae2019-95924","url":null,"abstract":"\u0000 Closed-cell stochastic foams are widely used in engineering field due to the excellent energy absorption capability. In this paper, the crushing response of three dimensional closed-cell foams is investigated under quasi-static and dynamic compression loading. Voronoi tessellation is employed to generate the mesoscale geometric models of closed-cell stochastic foams, and subsequently numerical analysis is carried out using LS-DYNA software. Results reveal that the plateau stress of Voronoi model under quasi-static compression linearly increases with the increase of relative density. In addition, the mechanical properties of Voronoi model under quasi-static and dynamic compression are related to a shear band collapse mode and a layer-wise collapse mode, respectively. The plateau stress and the densification strain under high-speed loading are higher than those under quasi-static and low-speed loading.","PeriodicalId":314553,"journal":{"name":"Volume 3: Structures, Safety, and Reliability","volume":"192 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":"116344594","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":"The Influence of Non-Prescriptive Legislation in the Evolution of Offshore Well Integrity Practices: An Exploratory Review","authors":"C. Morais, D. Abreu, J. Santos, M. Maturana, Danilo Colombo, M. Martins","doi":"10.1115/omae2019-96269","DOIUrl":"https://doi.org/10.1115/omae2019-96269","url":null,"abstract":"\u0000 Among the stochastic tools and risk analysis techniques, ALARP (As Low As Reasonably Practicable) concept has proved to be the most influential guidance regarding the development of regulations and standards of the offshore industry in terms of risk assessment and consequently of equipment integrity. The reasons for that can be traced back to early seventies, when the British Health and Safety Executive (HSE) released its seminal document “The Health and Safety at Work etc. Act 1974”. The 1974 Act was the first regulation to adopt a non-prescriptive approach as a basis to configure the ruling legislation of industrial activities. Since then, risk analysis methods have encountered a vast field of opportunities in the wide range of options proportionated by such framework. In this sense, the Safety Case and the NORSOK standards play a significant role in the non-prescriptive approach application in the offshore industry. The present work discusses the influence of these two frameworks in the definition of the current Brazilian offshore legislation, especially in terms of the design, tests, and monitoring of the so called Solidary Well Barriers throughout the well life cycle. The United States legislation, largely reviewed after the Macondo accident, will be used to counterpoint the prescriptive and non-prescriptive approaches.","PeriodicalId":314553,"journal":{"name":"Volume 3: Structures, Safety, and Reliability","volume":"10 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":"127121666","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":"Effect of Spectrum Tail Length on Modulational Instability and Freak Wave Occurrence in JONSWAP Sea States","authors":"C. Kirezci, A. Babanin","doi":"10.1115/omae2019-95740","DOIUrl":"https://doi.org/10.1115/omae2019-95740","url":null,"abstract":"\u0000 In this study, probability of freak wave occurrence due to modulational instability in JONSWAP sea states are investigated. This investigation has been conducted based on the quantitative indicators of instability in wave spectrum, which are two Benjamin-Feir index (BFI) [1,2] with different spectral bandwidth definitions and Π number [3]. Evolution of wave field are simulated using fully nonlinear phase-resolving Chalikov-Sheinin (CS) numerical model [4,5]. Initial sea surface is controlled with JONSWAP shape parameters (α and γ) and random initial phases. Effect of high frequency end of spectrum on modulational instability and freak wave evolution are discussed by considering 4 different tail lengths.\u0000 According to simulation results, all parameters that are considered here perform as an indicator for the occurrence of extreme events which makes it possible to define a certain interval for indicators, where freak wave occurrence probability is the highest and potentially dangerous, to be possibly used in extreme wave forecasting. Another key finding is that, modulational instability increases when high frequency part of spectrum is present (longer tail) as expected. Nevertheless, after certain nonlinearity, modulational instability is more prone to result in breaking which significantly decreases the probability of occurrence of freak events. Therefore, spectra with shorter tail length result in more dangerous sea states.","PeriodicalId":314553,"journal":{"name":"Volume 3: Structures, Safety, and Reliability","volume":"38 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":"125494608","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":"Experimental Assessment of Vertical Shear Force and Bending Moment in Severe Sea Conditions","authors":"B. Horel, B. Bouscasse, A. Merrien, G. D. Hauteclocque","doi":"10.1115/omae2019-96272","DOIUrl":"https://doi.org/10.1115/omae2019-96272","url":null,"abstract":"\u0000 Recent studies have benchmarked the prediction of wave vertical bending moment (VBM) of ship in waves [1][2], and found significant scatter among the numerical codes.\u0000 Unfortunately, experimental data in extreme waves, that are relevant to ship design, are not often easily accessible, nor completely fitted to rigorous comparison to numerical codes. Then, the improvement of numerical tools and the modelling of ship’s internal loads still requires accurate experimental data measured in steep waves (ratio wave height H to wavelength λ, H/λ = 0.1) where the ship behavior and loads are modified by non-linearities.\u0000 Thus, in order to validate simulation codes, which underlies rules requirement, and to establish criteria that makes ships safer to sail in severe sea conditions, experiments are carried out in the 50m × 30m × 5m hydrodynamic and ocean engineering tank of Ecole Centrale Nantes. A 1/65th scaled model of a 6750-TEU containership is used. The ship is moored and several combinations of wavelength and wave height are tested.\u0000 While segmented hulls are commonly instrumented with strain gauges, the present experiments are performed on a segmented hull with a 6DOF sensor located close to the amidship. This setting allows for a very stiff model which dramatically reduces the hydroelastic effects. According to previous study [1], the position of the sensor is chosen where the bending moment is supposed to reach a maximum value. The model motion is measured through a Qualisys IR tracking system and accelerometers are located on the fore and aft of the beam.\u0000 Also, each of the 9 segments is equipped with a 3DOF dynamometer to measure the hydrodynamic loads on the hull. This allows for recovering the hydrodynamic loads on the segments and then to compute the shear force and bending moment discretized all over the ship length. A comparison is therefore possible with the 6DOF sensor. Details of the computations are given in the paper.\u0000 A particular attention is paid to the reproducibility and repeatability of the tests. The innovative experimental setup and the measured data are presented in the paper. Based on previous studies [3], the effects of the non-linearities are also discussed.","PeriodicalId":314553,"journal":{"name":"Volume 3: Structures, Safety, and Reliability","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127268992","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":"Numerical Methods for Interlink Stiffness Formulations and Parameters Sensitivity of Out-of-Plane Bending in Mooring Chains","authors":"C. Edward, A. Dev","doi":"10.1115/omae2019-96042","DOIUrl":"https://doi.org/10.1115/omae2019-96042","url":null,"abstract":"\u0000 Mooring components used for offshore floaters are conventionally designed only to resist axial loads with minimum resistance to bending loads. However, the unprecedented failure of four mooring lines of the Girassol Buoy followed by new modifications of similar buoys exposed the gaps in the existing methodology for failure assessment. The root cause of this failure was attributed to the critical role of out-of-plane (OPB) bending induced fatigue which reduced the fatigue life by 95%. The methodology to incorporate OPB fatigue for failure assessments involves a complex process due to numerous parameters required in the formulations and variability of mooring configurations. One of the most critical steps required to simplify methodology is the formulation of the interlink stiffness, contact stiffness and global stiffness of the chain segment. Currently, the interlink stiffness is derived from full-scale laboratory testing which is expensive and has limitations in generating data for a range of configurations.\u0000 This paper focuses on producing the interlink stiffness using numerical simulations based on non-linear FE analysis to capture the complex interlink contacts mechanism at the mating surface, elastic-plastic material properties considering non-linear isotropic and non-linear kinematic behaviors during OPB response modes, and compare the numerical models based on available experimental data. The numerical model developed for this research are designed to replicate real case OPB scenarios which induces both rotation and vertical displacements at the mooring connection points. This is different from models studied so far that induces only vertical displacements to study OPB responses which produces conservative results.\u0000 Further to this, an exhaustive analysis of the key OPB inducing parameters like chain diameter, types, pre-tension, instantaneous tensions, proof loading, residual stress, material properties, boundary condition etc. are required for understanding the underlying failure mechanism. This research also investigates the key OPB parameters and analyze their inter-dependencies, proportionalities and relative sensitivities to understand their overall contribution to OPB failures. This paper presents the first part of this research work which focuses on some of these key aspects to generate the simplified methodology using numerical methods.\u0000 The findings of this research can be used to generate a database of interlink stiffness for application to a range of mooring configurations and develop mathematical formulations for carrying out a direct assessment of OPB fatigue in combination with tension-tension fatigue failures and proposes potential mechanisms for improving the fatigue life.","PeriodicalId":314553,"journal":{"name":"Volume 3: Structures, Safety, and Reliability","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125900400","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":"Application of Machine Learning Techniques As a Means of Mooring Integrity Monitoring","authors":"J. Gumley, H. Marcollo, S. Wales, A. Potts, C. Carra","doi":"10.1115/omae2019-96411","DOIUrl":"https://doi.org/10.1115/omae2019-96411","url":null,"abstract":"\u0000 There is growing importance in the offshore floating production sector to develop reliable and robust means of continuously monitoring the integrity of mooring systems for FPSOs and FPUs, particularly in light of the upcoming introduction of API-RP-2MIM. Here, the limitations of the current range of monitoring techniques are discussed, including well established technologies such as load cells, sonar, or visual inspection, within the context of the growing mainstream acceptance of data science and machine learning. Due to the large fleet of floating production platforms currently in service, there is a need for a readily deployable solution that can be retrofitted to existing platforms to passively monitor the performance of floating assets on their moorings, for which machine learning based systems have particular advantages.\u0000 An earlier investigation conducted in 2016 on a shallow water, single point moored FPSO employed host facility data from in-service field measurements before and after a single mooring line failure event. This paper presents how the same machine learning techniques were applied to a deep water, semi taut, spread moored system where there was no host facility data available, therefore requiring a calibrated hydrodynamic numerical model to be used as the basis for the training data set.\u0000 The machine learning techniques applied to both real and synthetically generated data were successful in replicating the response of the original system, even with the latter subjected to different variations of artificial noise. Furthermore, utilizing a probability-based approach, it was demonstrated that replicating the response of the underlying system was a powerful technique for predicting changes in the mooring system.","PeriodicalId":314553,"journal":{"name":"Volume 3: Structures, Safety, and Reliability","volume":"88 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122695362","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":"Four-Point Bending of Metallic I-Core Sandwich Beams With Longitudinal Girder","authors":"Wen Hu, Jun Liu, Pan Zhang, Yuansheng Cheng","doi":"10.1115/omae2019-95491","DOIUrl":"https://doi.org/10.1115/omae2019-95491","url":null,"abstract":"\u0000 I-core sandwich structure has great potential in the application of hull structure construction due to its high specific strength and relatively simple manufacturing process. The topic on the study of mechanical properties of I-core sandwich structure under bending loads is of interest to structural designers since the structure is often subjected to bending loads in engineering applications. In this paper, a metallic I-core sandwich beam with longitudinal girder was designed and manufactured using laser welding technique, and finally tested under four-point bend loading. The elastic-plastic behaviors and the ultimate load carrying capacity of this novel beam structure were obtained. A numerical model was developed to investigate the mechanical properties of this novel beam structure by finite element method. The results of the numerical model were compared with experimental data. Stress components of the front face and back face in the failure process were analyzed and discussed to investigate the failure of them. Results showed that the huge local bending stresses of plate caused the failure of the front face and back face. Finally, an improved scheme for the test was proposed to provide a pure bending load, which was proved by finite element simulation. All the findings aim to guide the engineering application of this structure.","PeriodicalId":314553,"journal":{"name":"Volume 3: Structures, Safety, and Reliability","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117077506","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}