Combined Loading Capacity of Pipelines: Approaches Towards the Compressive Strain Limit

2012 ◽  
Author(s):  
Hossein Karbasian ◽  
Steffen Zimmermann ◽  
Ulrich Marewski ◽  
Michael Steiner
Keyword(s):  
Boundary Conditions ◽  
Material Behavior ◽  
Combined Loading ◽  
Bending Test ◽  
Local Geometry ◽  
Line Pipe ◽  
Buckling Behavior ◽  
Definition Of ◽  
Selection Of ◽  
Modelling Approaches

This paper presents details on the load bearing capacity of pipelines subjected to combined loading (internal pressure, axial and bending load) based on the findings of a recent research project of the European Pipeline Research Group (EPRG). Firstly, the failure mechanisms of line pipe under combined loading, which depend on local geometry, material characteristics as well as local and global applied loading, are characterized. Afterwards, differences between laboratory testing and the real-life situation of pipelines subjected to combined loading are described. Here, optimal boundary conditions for realistic testing are defined. Finally, a large variety of modelling approaches, specifically dedicated to combined loading experimental data from 59 full-scale tests on line pipe joints have been analysed. The relevant parameters in the analysis of buckling behavior of the pipes were: actual material properties, boundary conditions, failure phenomena and strain at failure, with the final aim to issue recommendations with regard to the selection of modelling approaches, sensitivity towards input parameters as well as strain threshold values. For the prediction of the limit pipe deformation a large selection of equations suggested by various authors in terms of critical bending moment, critical strain and critical stress for various loading conditions were considered. The methods differ in solution methodology (analytical vs. numerical), in the definition of material behavior (elastic, elastic-plastic) and in the definition of critical conditions and critical points. Then, the different types of buckling as a function of pipe geometry were characterized. Finally, the buckling behavior of an actual bending test was simulated using measured input data.

On the Critical Boundary Conditions for Rupture of Buckled Steel Pipelines

2017 ◽  
Author(s):  
Nima Mohajer Rahbari ◽  
J. J. Roger Cheng ◽  
Samer Adeeb
Keyword(s):  
Boundary Conditions ◽  
Equivalent Plastic Strain ◽  
Operating Mode ◽  
Bending Test ◽  
Loading Path ◽  
Fe Model ◽  
Line Pipe ◽  
Steel Pipes ◽  
Critical Boundary ◽  
Soil Pipe

The environmental contamination due to the leakage of energy pipelines is a serious hazard to the public property and safety. Hence, any premature rupture should be dealt with in the design and the operating mode of steel pipes. A large amount of complexity is involved in the soil-pipe interactions that makes it so challenging to discover the physical boundary conditions (BC) applied to the buried pipelines during differential ground movements. Therefore, the most critical boundary conditions of buried pipes should be conceived based on the probable mechanism of soil-pipe interactions and considered in the experimental and analytical simulations of rupture. The focus of the current research is to address the critical boundary conditions that can trigger the rupture of underground wrinkled pipelines whilst being subjected to a monotonic increase of curvature. Finite element (FE) simulation of a full-scale bending test on a pressurized X70 line pipe specimen conducted at the University of Alberta is implemented. Cumulative fracture criterion coupled with the equivalent plastic strain to fracture for X70 steel grade is fed into the analysis to predict the ductile crack formation in the pipe’s body. The FE model is verified by the experimental data and is used to study the critical soil-pipe interactions that provoke the rupture of buckled steel pipes on the tensile side of the cross-section under increasing bending curvature. The results of this study suggest that the pipelines which are restricted from axial displacements are extremely vulnerable to experience a rupture along their post-buckling loading path. And so are the pipelines in which tensile axial force is developed due to soil-pipe interactions, e.g. pipelines in arctic regions that are installed during the summer time.

Benchmarking Severe Accident Computer Codes for Heavy Water Reactor Applications

2017 ◽  
Vol 3 (2) ◽  
Author(s):  
Thambiayah Nitheanandan ◽  
X. Cao ◽  
J.-H. Choi ◽  
D. Dupleac ◽  
D.-H. Kim ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
International Atomic Energy Agency ◽  
Heavy Water ◽  
Severe Accident ◽  
Energy Agency ◽  
Heavy Water Reactor ◽  
Computer Codes ◽  
Water Reactors ◽  
Definition Of ◽  
Selection Of

The International Atomic Energy Agency (IAEA) organized a coordinated research project (CRP) on “Benchmarking Severe Accident Computer Codes for Heavy Water Reactors (HWR) Applications,” (IAEA TECDOC Series No. 1727), and the activity was completed in 2012. This paper summarizes the results from the CRP: the selection of a severe accident sequence, definition of appropriate geometrical and boundary conditions, benchmarking code analyses, comparison of the code results, evaluation of the capabilities of existing computer codes to predict important severe accident phenomena, and suggestions for code improvements and/or new experiments to reduce uncertainties.

Selection of Deformation Modes for Flexible Multibody Dynamics

1987 ◽  
Author(s):  
S.-S. Kim ◽  
E. J. Haug
Keyword(s):  
Boundary Conditions ◽  
Gaussian Elimination ◽  
Flexible Multibody Dynamics ◽  
Coefficient Matrix ◽  
Flexible Beam ◽  
Equilibrium Equations ◽  
Definition Of ◽  
Flexible Component ◽  
Deformation Modes ◽  
Selection Of

Abstract This paper presents a method of selecting boundary conditions and deformation modes for redundantly constrained flexible components in mechanical system dynamics. Gaussian elimination is used to partition the coefficient matrix in equilibrium equations for each flexible component, leading to definition of a retained statically determinate set and a redundant set of boundary conditions. Methods for selection of deformation modes is presented, to account for deformation due to constraint reaction forces. A door closing mechanism and a moving flexible beam illustrate the method of selecting boundary conditions and the effectiveness of constraint modes for approximation for system dynamic response.

Energy-Derived, Damage-Based Failure Criterion for Fatigue Testing

2000 ◽  
Vol 1723 (1) ◽  
pp. 141-149 ◽  
Author(s):  
Khalid A. Ghuzlan ◽  
Samuel H. Carpenter
Keyword(s):  
Fatigue Testing ◽  
Fatigue Loading ◽  
Constant Stress ◽  
Material Behavior ◽  
Dissipated Energy ◽  
Initial Stiffness ◽  
Repeated Load ◽  
Definition Of ◽  
Selection Of

Determination of the failure limit in a repeated-load fatigue test in the laboratory has relied entirely on the arbitrary selection of a fixed criterion. The constant strain and constant stress modes of fatigue loading have been described by a consistent definition of failure in flexural fatigue testing because of the distinctly different application of energy during the loading history. The most widely accepted definition is a decrease in initial stiffness by 50 percent. Procedures examining energy input and dissipated energy have required different schemes for each mode in an attempt to describe similar states of damage in the mixture. A proposed method is presented for examining dissipated energy to select a consistent level of material behavior that is indicative of the damage accumulation in the mixture. This procedure shows the similarity between the constant stress and constant strain modes of testing and is shown to provide the potential for unifying the now phenomenological description of fatigue with a more rational energy-based description.

Thermo-Economic Optimization of the CCPP Design With Supplementary Firing Considering Off-Design Performance and Operating Profile

2011 ◽  
Author(s):  
Enrico Conte ◽  
Camille Pedretti
Keyword(s):  
Boundary Conditions ◽  
Process Model ◽  
Plant Design ◽  
Ambient Conditions ◽  
Design Rules ◽  
Water Steam ◽  
Plant Operator ◽  
Definition Of ◽  
Selection Of ◽  
Steam Cycle

This paper presents the latest developments of a methodology for the initial design of the water/steam cycle in combined-cycle power plants, which aims at delivering optimal designs from an operator’s perspective. To this end, an evolutionary algorithm optimization toolbox is coupled to a process model of the water/steam cycle. The process model requires the definition of a number of boundary conditions (like GT type and ambient conditions) and the selection of the cycle configuration (number of pressure levels, single or double reheat, supplementary firing, heat integration with GT coolers, fuel gas preheating, steam extraction from the steam turbine and type of cold end, among others). Based on a number of thermodynamic parameters assigned by the optimizer, the process model derives an initial dimensioning and/or selection of the key components and systems from the OEM’s portfolio: HRSG (full, geometry-based technical dimensioning), piping, steam turbines, condenser and generator, among others. For each of those, realistic designs are ensured by checking and enforcing the component design rules. Finally, performance and cost are derived. In the latest development, the process model computes the plant performance in a number of off-design conditions, specified in a plant operating profile. These may include different ambient conditions, GT loads, power augmentation (e.g. supplementary firing, inlet fogging and evaporative cooling) and steam exports (e.g. to district heating, desalination plant, carbon capture system) or imports (e.g. from a solar field). The cost of electricity (CoE), net present value (NPV) or average efficiency of the plant design in the given operating profile is the feedback to the optimization algorithm. This guides the process towards the definition of a plant design that gives the best thermo-economic performance under the specified economic boundary conditions and operating scenario. In a typical example, an air-cooled peaking plant needs to be optimized to maximize NPV in an operating scenario characterized by large spikes of the electricity price in hot summer days, during which the plant operator wants to use supplementary firing to boost power production. The described methodology is applied to find the most advantageous dimensions of the supplementary firing to be installed and the right HRSG design pressure at design conditions, ensuring that all design rules and technical limits are respected in all operating conditions. In this way, an optimal point is found in the trade-off between amount of supplementary firing and dimensions of HRSG and air-cooled condenser, delivering the highest possible benefit to the plant operator.

Selection and Preparation of Specific Tissue Regions For Tem Using Large Epoxy-Embedded Blocks

1973 ◽  
Vol 31 ◽  
pp. 324-325 ◽  
Author(s):  
P. M. Lowrie ◽  
W. S. Tyler
Keyword(s):  
Electron Microscopy ◽  
Anatomical Structures ◽  
Ultrastructural Studies ◽  
Transmission Electron ◽  
Microscopic Evaluation ◽  
Embedded Blocks ◽  
Specific Tissue ◽  
Definition Of ◽  
Areas Of Interest ◽  
Selection Of

The importance of examining stained 1 to 2μ plastic sections by light microscopy has long been recognized, both for increased definition of many histologic features and for selection of specimen samples to be used in ultrastructural studies. Selection of specimens with specific orien ation relative to anatomical structures becomes of critical importance in ultrastructural investigations of organs such as the lung. The uantity of blocks necessary to locate special areas of interest by random sampling is large, however, and the method is lacking in precision. Several methods have been described for selection of specific areas for electron microscopy using light microscopic evaluation of paraffin, epoxy-infiltrated, or epoxy-embedded large blocks from which thick sections were cut. Selected areas from these thick sections were subsequently removed and re-embedded or attached to blank precasted blocks and resectioned for transmission electron microscopy (TEM).

Buckling of Circular Cylindrical Shells Using a Displacement Function

1974 ◽  
Vol 96 (4) ◽  
pp. 1322-1327
Author(s):  
Shun Cheng ◽  
C. K. Chang
Keyword(s):  
Boundary Conditions ◽  
Axial Compression ◽  
Cylindrical Shells ◽  
External Pressure ◽  
Displacement Function ◽  
Combined Loading ◽  
Trial Solution ◽  
Governing Differential Equation ◽  
Circular Cylindrical Shells ◽  
The Stability

The buckling problem of circular cylindrical shells under axial compression, external pressure, and torsion is investigated using a displacement function φ. A governing differential equation for the stability of thin cylindrical shells under combined loading of axial compression, external pressure, and torsion is derived. A method for the solutions of this equation is also presented. The advantage in using the present equation over the customary three differential equations for displacements is that only one trial solution is needed in solving the buckling problems as shown in the paper. Four possible combinations of boundary conditions for a simply supported edge are treated. The case of a cylinder under axial compression is carried out in detail. For two types of simple supported boundary conditions, SS1 and SS2, the minimum critical axial buckling stress is found to be 43.5 percent of the well-known classical value Eh/R3(1−ν2) against the 50 percent of the classical value presently known.

scholarly journals Promotion of Resilience in Migrants: A Systematic Review of Study and Psychosocial Intervention

2021 ◽  
Author(s):  
Maria Ciaramella ◽  
Nadia Monacelli ◽  
Livia Concetta Eugenia Cocimano
Keyword(s):  
Systematic Review ◽  
Psychosocial Intervention ◽  
Life Experiences ◽  
Psychosocial Interventions ◽  
Migrant Population ◽  
Methodological Choices ◽  
Research Questions ◽  
Definition Of ◽  
Selection Of

AbstractThis systematic review aimed to contribute to a better and more focused understanding of the link between the concept of resilience and psychosocial interventions in the migrant population. The research questions concerned the type of population involved, definition of resilience, methodological choices and which intervention programmes were targeted at migrants. In the 90 articles included, an heterogeneity in defining resilience or not well specified definition resulted. Different migratory experiences were not adequately considered in the selection of participants. Few resilience interventions on migrants were resulted. A lack of procedure’s descriptions that keep in account specific migrants’ life-experiences and efficacy’s measures were highlighted.

scholarly journals Shape Sensing of a Complex Aeronautical Structure with Inverse Finite Element Method

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1388
Author(s):  
Daniele Oboe ◽  
Luca Colombo ◽  
Claudio Sbarufatti ◽  
Marco Giglio
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Boundary Conditions ◽  
Strain Field ◽  
Element Analysis ◽  
Inverse Finite Element Method ◽  
Shape Sensing ◽  
Definition Of ◽  
High Level ◽  
Element Method

The inverse Finite Element Method (iFEM) is receiving more attention for shape sensing due to its independence from the material properties and the external load. However, a proper definition of the model geometry with its boundary conditions is required, together with the acquisition of the structure’s strain field with optimized sensor networks. The iFEM model definition is not trivial in the case of complex structures, in particular, if sensors are not applied on the whole structure allowing just a partial definition of the input strain field. To overcome this issue, this research proposes a simplified iFEM model in which the geometrical complexity is reduced and boundary conditions are tuned with the superimposition of the effects to behave as the real structure. The procedure is assessed for a complex aeronautical structure, where the reference displacement field is first computed in a numerical framework with input strains coming from a direct finite element analysis, confirming the effectiveness of the iFEM based on a simplified geometry. Finally, the model is fed with experimentally acquired strain measurements and the performance of the method is assessed in presence of a high level of uncertainty.

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