Limit State Philosophy in Pipeline Design

1987 ◽  
Vol 109 (1) ◽  
pp. 9-22 ◽  
Author(s):  
C. P. Ellinas ◽  
P. W. J. Raven ◽  
A. C. Walker ◽  
P. Davies
Keyword(s):  
Structural Analysis ◽  
Safety Factor ◽  
Current Knowledge ◽  
Limit State ◽  
Structural Behavior ◽  
Major Conclusion ◽  
Safety Factors ◽  
Suitable Framework ◽  
General Aspects ◽  
Pipeline Design

This paper considers the application of the limit state philosophy of structural analysis to pipeline design. General aspects of the philosophy are discussed and the approach to the evaluation of safety factors is reviewed. The paper further considers the various limit and serviceability states which would be relevant to a pipeline and reviews the various factors which may require consideration, before a code embodying the limit state philosophy could be formulated. A review of the state of current knowledge on various aspects of geometry and material characteristics, loading and structural behavior is presented. It is intended that such a review can be used as the basis for a larger study to provide guidance and data for the evaluation of rational levels of safety factor. The major conclusion reached by the authors is that a limit state philosophy would be valuable in providing a suitable framework, which may highlight the significant aspects of pipeline design and which can most easily accommodate new requirements and results obtained from research.

Safety Factors Calibration for Wall Thickness Design of Ultra Deepwater Pipelines

2013 ◽  
Author(s):  
Eduardo Oazen ◽  
Bruno R. Antunes ◽  
Carlos O. Cardoso ◽  
Rafael F. Solano
Keyword(s):  
Safety Factor ◽  
Wall Thickness ◽  
Structural Reliability ◽  
Limit State ◽  
Large Diameter ◽  
Design Codes ◽  
Safety Factors ◽  
Offshore Pipeline ◽  
Reliability Methods ◽  
Pipeline Design

Wall thickness often presents a considerable influence in offshore pipeline capital expenditure (CAPEX). This influence is enhanced in design of ultra deepwater trunk lines of large diameter, where any wall thickness increase provides a huge impact on project costs. In ultra deepwater scenarios, thicker pipelines may eventually implicate not only in higher costs, but may also compromise the project feasibility due to installation load constraints related to laying vessels availability. One potential way to reduce the pipeline wall thickness is to calibrate fitness-for-purpose safety factors through application of structural reliability methods, instead of utilizing the standardized safety factors presented in international codes. Since mid-nineties, several offshore pipeline design codes have been allowing the calibration of safety factors by structural reliability analysis. The purpose of such an allowance is that structural reliability methods would eliminate some eventual conservatism presented in the safety factors proposed by codes. Although this enables the achievement of optimized safety factors, more than fifteen years have passed and only few pipeline projects have taken advantage of the benefits of safety factor calibration. This paper evaluates which potential benefits are available through safety factor calibration, particularly for wall thickness reduction purposes in ultra deepwater pipeline design. Calibrated safety factors are presented for some scenarios related to ultra deepwater export pipelines, considering “system collapse criteria” limit state. The calibrated safety factors are compared with the standardized safety factors presented by international pipeline design codes. The potential for safety factor reduction by the utilization of linepipes with more stringent manufacturing tolerances and the consideration of the thermal ageing imposed by coating application are also discussed.

scholarly journals Dimensioning of silicone adhesive joints: Eurocode-compliant, mesh-independent approach using the FEM

2020 ◽  
Vol 5 (3) ◽  
pp. 349-369 ◽  
Author(s):  
Micheal Drass ◽  
Michael A. Kraus
Keyword(s):  
Finite Element ◽  
Safety Factor ◽  
Limit State ◽  
Adhesive Joints ◽  
State Function ◽  
Limit State Function ◽  
Element Calculation ◽  
Safety Factors ◽  
Silicone Adhesive ◽  
Level I

Abstract This paper deals with the application of the semi-probabilistic design concept (level I, DIN EN 1990) to structural silicone adhesives in order to calibrate partial material safety factors for a stretch-based limit state equation. Based on the current legal situation for the application of structural sealants in façades, a new Eurocode-compliant design concept is introduced and compared to existing design codes (ETAG 002). This is followed by some background information on semi-probabilistic reliability modeling and the general framework of the Eurocode for the derivation of partial material safety factors at Level I. Within this paper, a specific partial material safety factor is derived for DOWSIL 993 silicone on the basis of experimental data. The data were then further evaluated under a stretch-based limit state function to obtain a partial material safety factor for that specific limit state function. This safety factor is then extended to the application in finite element calculation programs in such a way that it is possible for the first time to perform mesh-independent static calculations of silicone adhesive joints. This procedure thus allows for great optimization of structural sealant design with potentially high economical as well as sustainability benefits. An example for the static verification of a bonded façade construction by means of finite element calculation shows (i) the application of EC 0 to silicone adhesives and (ii) the transfer of the EC 0 method to the finite element method with the result that mesh-independent ultimate loads can be determined.

Improved defibrillator waveform safety factor with biphasic waveforms

1983 ◽  
Vol 245 (1) ◽  
pp. H60-H65 ◽  
Author(s):  
J. L. Jones ◽  
R. E. Jones
Keyword(s):  
Safety Factor ◽  
Voltage Gradient ◽  
Excitation Threshold ◽  
Efficacy And Safety ◽  
Myocardial Cells ◽  
Safety Factors ◽  
Adult Type ◽  
Intracellular Microelectrodes ◽  
Cultured Myocardial Cells

Excitation thresholds and arrhythmias were studied in "adult-type" cultured chick embryo myocardial cells after electric field stimulation with biphasic, truncated, and rectified underdamped RLC (resistance-inductance-capacitance) type waveforms, to test the hypothesis that the negative phase of biphasic waveforms ameliorates membrane dysfunction induced by the initial positive portion. Photocell mechanograms and intracellular microelectrodes monitored extrasystoles and depolarization-induced arrhythmias. Rectifying or truncating biphasic waveforms did not alter the excitation threshold. However, shock intensities producing specific postshock arrhythmias or a specific severity of postshock prolonged depolarization differed significantly when biphasic waveforms were truncated or rectified. The voltage gradient producing a specific dysfunction was 12-14% lower for the truncated version than for the biphasic; that for the rectified version was 17-27% lower than for the biphasic version (although both contained the same energy). Safety factor, the ratio between shock intensity producing specific dysfunction and that producing excitation, was determined for each waveform. Biphasic waveforms had larger safety factors than truncated or rectified waveforms. Since safety factor, as measured in cultured myocardial cells, closely corresponds with in situ defibrillating effectiveness (14), the significantly higher safety factors of biphasic waveforms suggest that carefully shaped biphasic waveforms might improve the efficacy and safety of cardiac defibrillation procedures.

scholarly journals Performance of asmetric structures reviewed with based plastic design performance (case study of application on building in Pekan Baru)

2020 ◽  
Vol 156 ◽  
pp. 05021
Author(s):  
Jati Sunaryati ◽  
Nidiasari ◽  
Alfadian
Keyword(s):  
Structural Analysis ◽  
Performance Analysis ◽  
Energy Method ◽  
Structural Behavior ◽  
Structural Performance ◽  
Plastic Design ◽  
Prone Area ◽  
Zonation Maps ◽  
Thrust Load

Performance-Based Plastic Design (PBPD) is a structural analysis that can be used to review structural performance. This method is increasingly popular to be used in the earthquake-prone area. This method is based on energy method that can be applied to steel or concrete structures. Meanwhile, Indonesia has already SNI 1726:2102 to be used as a guide in designing the thrust load to review the level of structural performance. Both of these things need to be used as a reference in areas that were initially considered safe from the earthquake but based on the development of earthquake micro zonation maps, it is very possible to become potential areas that also become earthquake regions. For this reason, the case of the structure that was built in the Pekanbaru area was taken. From the analyses of structural behavior, the structure that applied PBPD has greater displacement than the structures that apply the thrust load of SNI 1726: 2012. The percentage of displacement that occurred was 8-37 %. Based on performance analysis, the structures according to PBPD shows a better level of performance to the application of SNI 1726: 2012 thrust load.

Safety Factor in Fatigue Under Fluctuating Stresses

1987 ◽  
Vol 109 (4) ◽  
pp. 397-401 ◽  
Author(s):  
V. A. Avakov
Keyword(s):  
Safety Factor ◽  
High Cycle Fatigue ◽  
Stress Amplitude ◽  
Static Strength ◽  
Mean Stress ◽  
Cycle Fatigue ◽  
Safety Factors ◽  
Generalize Expression ◽  
Allowable Stresses ◽  
Number Of Cycles

It is common to assume identical allowable safety factors in static strength [m], defined by mean stress (Sm), and in fatigue [a], defined by stress amplitude (Sa), in order to find the full safety factor (F) under asymmetrical cycles, or to plot any type of the Sm–Sa diagram of allowable stresses. Here additional modification is considered to generalize expression of the full factor of safety in fatigue under asymmetrical stresses, utilizing unequal allowable safety factors in static strength (by mean stress) and in fatigue (by stress amplitude): ([a] ≠ [m]). We assume that loading is stationary, and cumulated number of cycles is large enough to consider high cycle fatigue.

Substantiation of probabilistic safety factors as a factor for optimizing the metal consumption of pipelines and the permissible operating pressure

2021 ◽  
pp. 364-371
Author(s):  
Юрий Григорьевич Матвиенко ◽  
Дмитрий Александрович Кузьмин ◽  
Владимир Васильевич Зацаринный ◽  
Максим Сергеевич Пугачев ◽  
Владимир Вячеславович Потапов
Keyword(s):  
Safety Factor ◽  
Probability Of Failure ◽  
Fracture Probability ◽  
Operating Pressure ◽  
Pipe Steels ◽  
Safety Factors ◽  
Metal Consumption ◽  
Load Variation ◽  
Coefficients Of Variation ◽  
The Given

Проведен анализ влияния коэффициентов вариации сопротивления материала разрушению и коэффициентов вариации нагрузки на вероятность разрушения и, следовательно, на коэффициенты запаса по характеристикам сопротивления материала разрушению при заданных показателях вероятности разрушения. Снижение неопределенности в условиях нагружения и повышение качества материала позволяют снизить коэффициенты запаса по пределу текучести и вязкости разрушения для заданных целевых показателей безопасности. На примере трубных сталей марок Ст 20 и 16ГС показана возможность снижения коэффициента запаса по пределу текучести до значений n = 1,45 при коэффициенте вариации нагрузки 0,1 и сохранении целевого показателя безопасности в терминах вероятности разрушения на уровне 10. Возможность снижения коэффициентов запаса по пределу текучести и вязкости разрушения при заданных целевых показателях безопасности в терминах вероятности разрушения позволяет оптимизировать металлоемкость и максимальные допустимые давления в эксплуатируемых трубопроводах. The analysis of the influence of the coefficients of variation of the material resistance and the coefficients of the load variation on the probability of failure as well as on the safety factors for the characteristics of the material resistance to failure has been done at given indicators of the probability of failure. Reducing uncertainty under loading conditions and improving material quality allow reducing the safety factors against fracture and collapse for given targets safety. Using the example of pipe steels of grades St 20 and 16GS, it seems possible to reduce the safety factor against collapse up to 1.45 with a load variation coefficient of 0.1 and maintaining the safety target in terms of the fracture probability at the level of 10. The possibility of reducing the safety factors against collapse and fracture at the given target safety indicators in terms of the fracture probability allows optimizing the metal consumption and the maximum allowable pressures in the operating pipelines.

Lumped Damage Mechanics

2015 ◽  
pp. 362-411
Keyword(s):  
Structural Analysis ◽  
Fracture Mechanics ◽  
Structural Damage ◽  
Damage Mechanics ◽  
Structural Behavior ◽  
Numerical Implementation ◽  
Plastic Range ◽  
Structural Collapse ◽  
Framed Structures ◽  
Damage And Fracture

As aforementioned, buildings in seismic zones must be designed to behave elastically under service loads or earthquakes of small intensity, and they can enter in the plastic range for events of intermediate intensity. Severe earthquakes are defined as those that are improbable but not impossible to happen during the lifetime of the structure. In these cases, structural damage, even damage that cannot be repaired, is allowed as long as there is no structural collapse. In order to design or certify safe structures, it is necessary to have computational tools that allow for the quantification of structural damage and that are able to describe structural behavior accurately near collapse. The elasto-plastic models present serious limitations in this sense. Damage and fracture mechanics represent a more rational option. The goal of this chapter is to describe how the concepts presented in Chapter 9 can be included in the mathematical models for the analysis of framed structures and its numerical implementation in structural analysis programs.

Performance-Based Seismic Design

2012 ◽  
pp. 23-50 ◽  
Author(s):  
Oscar Möller ◽  
Marcelo Rubinstein ◽  
Fabián Savino ◽  
Ricardo O. Foschi
Keyword(s):  
Neural Networks ◽  
Structural Analysis ◽  
Earthquake Engineering ◽  
Optimization Algorithm ◽  
Limit State ◽  
Design Parameters ◽  
Total Cost ◽  
Operational Life ◽  
Performance Based Seismic Design ◽  
Dynamic Structural Analysis

An approach is presented to structural optimization for performance-based design in earthquake engineering. The objective is the minimization of the total cost, including repairing damage produced by future earthquakes, and satisfying minimum target reliabilities in three performance levels (operational, life safety, and collapse). The different aspects of the method are considered: a nonlinear dynamic structural analysis to obtain responses for a set of earthquake records, representing these responses with neural networks, formulating limit-state functions in terms of deformations and damage, calculating achieved reliabilities to verify constraint violations, and the development of a gradient-free optimization algorithm. Two examples illustrate the methodology: 1) a reinforced concrete portal for which the design parameters are member dimensions and steel reinforcement ratios, and 2) optimization of the mass at the cap of a pile, to meet target reliabilities for two levels of cap displacement. The objective of this latter example is to illustrate model effects on optimization, using two different hysteresis approaches.

STRUCTURAL ANALYSIS OF CARBON COMPOSITE FRAME FOR FOLDABLE ELECTRIC WHEELCHAIR DEVELOPMENT

2019 ◽  
Vol 19 (07) ◽  
pp. 1940045
Author(s):  
WOO SUK CHONG ◽  
MI YEON SHIN ◽  
CHANG HO YU
Keyword(s):  
Structural Analysis ◽  
Compressive Stress ◽  
Safety Factor ◽  
Carbon Composite ◽  
The Body ◽  
Frame Structure ◽  
Structural Safety ◽  
Maximum Displacement ◽  
Electric Wheelchair ◽  
Maximum Variation

Electric wheelchairs developed so far have difficulties for elderly people to use, because of their bulkiness and heavy weight. To address this problem, this study presents a design for the construction of an electric wheelchair with an application of light duty materials at frame and a foldable structure that can be easily loaded in a narrow space. A structural analysis was performed to evaluate the structural safety of the foldable wheelchair. For the purpose of analysis, a carbon composite was used as the material for the frame; Structure Mechanics Module of COMSOL Multiphysics was used as the analysis software; and for the boundary condition, the lower part of the body frame was fixed, and a load of 150[Formula: see text]kg was applied to the upper part of the wheelchair. According to the results of the structural analysis, a maximum displacement of 2.869[Formula: see text]mm occurred at the handle where the carbon composite was applied, and tensile and compressive stress of 103[Formula: see text]MPa and 107.3[Formula: see text]MPa, respectively, were measured at the seat part of the wheelchair where the load was applied. The safety factors were 7.5 and 5.5 for tensile stress and compressive stress, respectively. A maximum variation of 0.0872[Formula: see text]mm occurred at the aluminum wheel shaft, and a maximum variation of 0.2046[Formula: see text]mm occurred at the joint. The maximum stress was 116.3[Formula: see text]MPa that corresponded to a safety factor of 2.66; this indicates that the wheelchair can be considered to be structurally safe as the safety factor exceeds the initial target of 2.

Hydraulic conductance of lung endothelial phenotypes and Starling safety factors against edema

2007 ◽  
Vol 292 (2) ◽  
pp. L378-L380 ◽  
Author(s):  
James C. Parker
Keyword(s):  
Endothelial Cell ◽  
Safety Factor ◽  
Hydraulic Conductance ◽  
Safety Factors ◽  
Edema Formation ◽  
Exercise Induced ◽  
Permeability Studies ◽  
A Minor ◽  
Cell Phenotypes ◽  
Alveolar Capillary

Recent permeability studies comparing endothelial cell phenotypes derived from alveolar and extra-alveolar vessels have significant implications for interpreting the mechanisms of fluid homeostasis in the intact lung. These studies indicate that confluent monolayers of rat pulmonary microvascular endothelial cells had a hydraulic conductance ( Lp) that was only 5% and a transendothelial flux rate for 72-kDa dextran only 9% of values determined for rat pulmonary artery endothelial cell monolayers. On the basis of previous studies partitioning the filtration coefficients between alveolar and extra-alveolar vascular segments in rat lungs and previous studies of lymph albumin fluxes and permeability, the contribution of the alveolar capillary segment to total albumin flux in lymph was estimated to be less than 10%. In addition, the Starling safety factors against the edema calculated for the alveolar capillaries are quite different from those estimated for whole lung. Estimates of the edema safety factor due to increased filtration across the alveolar capillary wall based on the low Lp indicate it is quantitatively the greatest safety factor, although it would be a minor safety factor for extra-alveolar vessels. Also, a markedly higher effective protein osmotic absorptive force for plasma proteins must occur in the capillaries relative to extra-alveolar vessels. The lower Lp for alveolar capillaries also has implications for the sequence of hydrostatic edema formation, and it also may have a role in preventing exercise-induced alveolar flooding.

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