Deterministic Leak-Before-Break Treatment of Uncertainties: Part 2 – Example Application

A leak-before-break strategy for CANDU primary piping systems

In practical applications, the stress status of expanded tubes is a critical parameter to control leakage and stress corrosion cracking. Therefore, it is important to study and analyze the stress distribution generated from tube expansion. Unfortunately, there are only a few theoretical approaches available for estimating the stress distribution of formed tubes, especially for cases where the expansion is achieved with spherical and oval dies. In this study, 3/8 stainless steel and copper tubes were expanded with an oval die in a designed test workbench, and the tangential and longitudinal strains were monitored during the expansion process. A new analytical approach is developed to estimate the stresses and strains in the expanded tube during the expansion process. The different expanded zones are treated using different theories. An axisymmetric finite element model as a numerical approach is used to analyze the stresses based on a multi-linear kinematic hardening behavior to validate the analytical approach. In addition, the stresses in the expanded tube and the push force of the die are also provided by the analytical, numerical and experimental approaches. Finally, the results from the three approaches are in a relatively good agreement.

In recent years, the global buckling assessment of offshore pipelines in High Pressure-High Temperature (HPHT) condition become increasingly challenging since more complex pipeline system arrangement e.g. pipe(s) or cable(s) is strapped onto a larger pipeline, are rapidly utilized in many areas. Yet, the detailed guideline to assess the buckle of bundles remains unclear, therefore this study will focus to investigate on a methodical and reproducible approach to analyze in-service buckling behavior of bundled offshore pipeline system. The global buckling behavior of bundled offshore pipeline system in this study is investigated using commercial Finite Element (FE) software. Two carbon steel pipelines with different diameter are bundled and the buckling behavior is studied under the influence of buckle triggers. In the actual condition, the rogue buckle trigger is generated from OOS (out of straightness) or imperfection e.g. due to laying tolerance. Varying dimension parameter such as diameter ratio between the main pipeline and strapped pipeline are considered to understand the impact of this parameter on the buckle behavior. The study begins with a comparison of the results using numerical and analytical approaches on a straight pipeline in an unbuckled condition for validation purposes. The design parameters including wall thickness, process data, and pipe-soil interaction data, are varied since it influences the buckle behavior. In addition, some design parameter such as material properties and pipeline length will be adopted from a typical offshore pipeline project and the values are fixed so the exercise can focus on the most governing parameters. Following this, two numerical modelling methods, the equivalent properties method and the connector method, are presented in this study to simulate bundled systems. With a good agreement between the analytical and numerical approach, some buckle trigger is introduced on the numerical model of the bundled pipeline so the system is able to buckle and the behavior can be evaluated further. The strain level, lateral displacement, axial feed-in and pipe integrity shall be reported in the post-buckle conditions for both main pipe and strapped pipe as per current code and standard requirement. With more reliable results of buckling assessment for bundled pipeline system, it gives technical confidence and a major saving in both Capital Expenditure (CAPEX) and Operational Expenditure (OPEX). Industry has put serious effort through various Joint Industry Projects (JIP) to develop the global buckling assessment guideline in order to ensure long term integrity operation. Although the JIP guideline is predominantly for single pipeline system, similar assessment is demanded also for bundled pipeline system which described in this study. Key findings of the assessment are presented along with an overview of the design process and the typical mitigation techniques to be considered for similar subsea pipeline projects.

Although much research focuses on investigating the responses of reinforced concrete (RC) structures under sole impact or blast loads, the responses of RC structures under a combination of impact and blast loads currently represent a gap in our knowledge. The combined actions of impact and blast loadings may be applied to RC structures during accidental or intentional collision of vessels, vehicles, etc., carrying explosive materials. A comprehensive study on the vulnerability of various structural members is carried out using finite element (FE) simulations under combination of impact and blast loads with the variations of various loading- and structural-related parameters and key parameters. This book introduces various structural analysis approaches for concrete structures when subjected to extreme loads such as impact and blast loadings. The theory of the combinations of impact and blast loads is proposed that can provide primary insights to the specific readers to develop new ideas in impact and blast engineering, including combined actions of extreme loads arising from real-world intentional or accidental events. This book will be of value to students (undergraduate or postgraduate), engineers, and researchers in structural and civil engineering, and specifically, those who are studying and investigating the performances of concrete structures under extreme loads.

Deep learning characterization of brain tumours with diffusion weighted imaging

A new simplified meta-model to evaluate the transmission of ground movements to structures integrating the elastoplastic soil behavior

This paper discusses a comprehensive analysis and quantitative assessment of two decades of nondestructive evaluation probability of detection (NDE POD) data collected using the Code of Federal Regulations’ (CFR)-approved NDE methods for railroad tank cars. The results obtained from this research demonstrate that these methods were not capable of achieving or approaching a 90-percent POD with 95-percent confidence (90/95 POD) for fatigue cracks in the butt weld (BW) test panels from the operators who participated in this research. The evaluation of the fillet weld (FW) data showed mixed results, but only the magnetic particle testing (MT) method reached 90/95 POD. Also, excessive false calls were observed in both the BW and the FW inspection results. These results indicate the variability in 1) NDE tests and calibration procedures, 2) operator variance, and 3) the influence of human factors on the application of the NDE inspection processes.

Identifying key process parameters for uncertainty propagation in environmental life cycle assessment for sewage sludge and food waste treatment

A numerical approach for computing standard errors (SES) of a linear equating is described. In the proposed approach, the first partial derivatives of the equating function needed to compute the SES are derived numerically. Thus, the difficulty of deriving the analytical formulas of the partial derivatives for a complicated equating method is avoided. The numerical and analytical approaches were compared using the Tucker equating method. The SES derived numerically were found to be indistinguishable from the SES derived analytically. In a computer simulation of the numerical approach using the Levine equating method, the SES based on the normality assumption were found to be less accurate than those derived without the normality assumption when the score distributions were skewed.

The transmission and reflection of electromagnetic waves impinging on metallic surfaces with periodically distributed slits (diffraction gratings) have been the subject of thorough studies using numerical and experimental approaches. Of special interest are the properties of the so-called compound gratings, which are periodic arrays of slits whose unit cell contains several of them. The transmission properties of such diffraction gratings have been studied along the last few years both theoretically (D.C. Skigin and R.A. Depine, Phys. Rev. Lett., 95, 217402, 2005) and experimentally (A.P. Hibbins et al., Phys. Rev. Lett., 96, 257402, 2006; M. Navarro-Ca et al., App. Phys. Lett., 94, 091107, 2009). However, analytical models are very useful for design purposes and, moreover, they provide physical insight that is not obvious from numerical approaches. For compound transmission gratings, the authors of this contribution recently developed a circuit-model-based analytical approach (F. Medina, F. Mesa and D.C. Skigin, IEEE Trans. on Mic. Theory Tech., 58, 105–115, 2010) that captures the essential physics of these optical systems. Thus, compound transmission gratings are now well understood, and numerical or analytical design tools are available.

Pushover analysis of soft brick unreinforced masonry walls using analytical and numerical approaches

The present work is an attempt to offer a comprehensive review of literature contributions, phenomenology and relevant results on water-mist systems. In particular, the water mist characterization and behavior in the field of fire con- trol and suppression have been identified as the main areas of investigation. Some key parameters have been analyzed to gain a quantitative evaluation of the physical phenomena related to water-mist systems. The water-mist fire suppression systems are an excellent alternative to halon fire protection systems, and they are now be- ing used in many areas, including marine and industrial applications. Therefore, a wide survey of the complete number of literature works on this topic would exceed the full length of the present paper and only some examples of important con- tributions will be mentioned here. This paper proposes an introductory list of relevant literature works and this reference survey is then deepened with work and result details on suppression mechanisms, spray characterizations and experimen- tal and numerical approaches. The final summary stresses out that a lot of experimental and numerical research and much application experience are still needed to gain better knowledge on water-mist systems, even if they already seem to be very promising in terms of efficiency and potentialities in fire control and suppression.

Humanitarian logistics operations perform challenging tasks while responding to large-scale natural disasters. Decision makers at different stages of humanitarian operations exploit numerous problem-specific decision-making models or tools. When synchronising the outputs (decisions) from models into a unified solution, the situation becomes critical because of the lack of consensus on objectives and the availability of model alternatives with uncertainty in the models' key parameters and evaluation of the models' alternative outcomes. Thus, the operational environment becomes complex to respond urgently to humanitarian needs and makes the situation deeply uncertain. In this paper, we inspect humanitarian logistics problems and available deep uncertainty approaches to identify the adapting needs in the latter to be applicable to the former. Our research findings indicate that deep uncertainty approaches should incorporate the concept of short-term planning by considering time constraints, bounded process iteration, data transformation technique, handling process failure, and ways of identifying model assumptions.

Application of fracture mechanics methods in safety analysis of piping components in subcreep and creep behavior

Hydrocarbon and non-hydrocarbon gas injection are among the most effective methods to enhance oil recovery. A key design parameter in any gas injection project is the minimum miscibility pressure (MMP). MMP can be measured in the laboratory with slim tube test, rising bubble apparatus and vanishing-interfacial-tension. Although laboratory measurements are more reliable, their high cost and longer period of time to get a few data sets made them less advantageous. There are numerous analytical, numerical, and empirical approaches devised to determine the MMP through studying thermodynamic behavior of reservoir and injection fluids in a given reservoir condition. Some numerical approaches need additional fluid and rock interaction properties such as relative permeability and capillary pressure. Conceptually, miscibility between injected gas and reservoir oil can occur through three multi-contact mechanisms, namely condensing drive mechanism (CDM), vaporizing drive mechanism (VDM) and both condensing and vaporizing (CV) drive mechanism. Some models such as single-cell algorithm usually give overestimated MMP values since the model is based on the assumption that the drive mechanism is dictated only by CDM or VDM. In most cases, as we will see from the case studies of this research and reported by others as well, miscibility develops through both condensing and vaporizing (CV) driving mechanisms. Multiple mixing cell approach is a very effective way to handle CV drive mechanism. In this study, we modify the algorithm proposed by Ahmadi and Johns (2008), by including additional checking criterion. In spite of increased computational time overhead, our added checking criterion is found to be very useful to crosscheck the validity of the determined MMP, hence improve the reliability.