Simplified Strength Reliability and Integrity Analysis of TTRs

2014 ◽  
Author(s):  
Mir Emad Mousavi ◽  
Sanjeev Upadhye ◽  
Kevin Haverty
Keyword(s):  
Extreme Events ◽  
Structural Reliability ◽  
Probability Distributions ◽  
Probabilistic Approach ◽  
Reliability Assessment ◽  
Cost Effective ◽  
Probability Of Failure ◽  
Annual Probability ◽  
Reliability Methods ◽  
Integrity Analysis

The design of riser systems can be improved if structural reliability methods are used to assess their safety and integrity and confirm that such design meets a target annual probability of failure. TTRs are typically multi–bore assemblies involving several sub-assemblies. The failure of any of the components of a TTR under extreme or service environmental conditions can lead to an immediate failure of the entire assembly and impose a direct risk of damaging the wellheads, conductors, casing and tubing hangers, or other subsea equipment, because they are installed directly on top of the wellhead. However, the actual strength safety of the TTR cannot be examined unless after it is installed and examined under extreme events. Because of the numerous uncertainties associated with the design of TTRs, a probabilistic approach based on structural reliability methods can account for many of those uncertainties and serve as a basis for their reliable and cost-effective design. In turn, a comprehensive reliability assessment of a TTR requires extensive analysis that is considerably more complex and time consuming compared to a conventional deterministic-based analysis. This paper presents a probabilistic-based simplified methodology for the strength reliability assessment of TTR systems. In this method, marginal values on some uncertain model inputs are considered similar to the conventional analysis methods but, some key random variables related to environmental demands and component capacities are considered with their associated probability distributions. As a result, this method can be used to estimate the minimum level of safety of the TTR under extreme events. Additionally, results of the proposed method are discussed for integrity analysis and integrity-based optimal design of the TTR system, which compare the safety of the TTR components and estimate the component Optimality Factors for improving the design integrity and meeting a target minimum annual probability of failure.

Utilizing In-Line Inspection Data and Structural Reliability Analysis to Set a Defendable Corrosion Re-Assessment Interval

2006 ◽  
Author(s):  
Ryan Sporns ◽  
Steven Bott ◽  
David Playdon
Keyword(s):  
Growth Rate ◽  
Software Package ◽  
Structural Reliability ◽  
Probability Of Failure ◽  
Simulation Based ◽  
Reliability Methods ◽  
Inspection Data ◽  
Integrity Analysis ◽  
Operation Characteristics ◽  
Pipeline Corrosion

A quantitative pipeline integrity analysis based on structural-reliability methods has been used to establish corrosion re-assessment intervals from in-line inspection data. This process, as implemented in a simulation-based software package, incorporates in line inspection (ILI) data, physical and operation characteristics of the pipeline, corrosion growth rate projections, and the uncertainties inherent in this information, to estimate the probability of failure (POF) as a function of time. Using this approach, the POF value is calculated on a joint-by-joint basis and the calculated values are then compared with an acceptable POF level to verify the integrity of each joint in any given year. Based on this information a re-assessment interval is established and selected joints are targeted for excavation and repair to ensure that the acceptable POF level is not exceeded.

Efficient Reliability Assessment With the Conditional Probability Method

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Rami Mansour ◽  
Mårten Olsson
Keyword(s):  
Conditional Probability ◽  
Structural Reliability ◽  
A Priori ◽  
Reliability Assessment ◽  
Probability Of Failure ◽  
Assessment Method ◽  
Probability Method ◽  
Probability Of Survival ◽  
Design Variables ◽  
Reliability Method

Reliability assessment is an important procedure in engineering design in which the probability of failure or equivalently the probability of survival is computed based on appropriate design criteria and model behavior. In this paper, a new approximate and efficient reliability assessment method is proposed: the conditional probability method (CPM). Focus is set on computational efficiency and the proposed method is applied to classical load-strength structural reliability problems. The core of the approach is in the computation of the probability of failure starting from the conditional probability of failure given the load. The number of function evaluations to compute the probability of failure is a priori known to be 3n + 2 in CPM, where n is the number of stochastic design variables excluding the strength. The necessary number of function evaluations for the reliability assessment, which may correspond to expensive computations, is therefore substantially lower in CPM than in the existing structural reliability methods such as the widely used first-order reliability method (FORM).

scholarly journals Calculation of Failure Probability of Constantly Loaded Cantilever Beam by Monte Carlo Method

2014 ◽  
Vol 17 (3) ◽  
pp. 80-82
Author(s):  
Dušan Páleš ◽  
Milada Balková ◽  
Ingrid Karandušovská
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Cantilever Beam ◽  
Probability Distributions ◽  
Probabilistic Approach ◽  
Constant Load ◽  
Probability Of Failure ◽  
The Subject ◽  
Individual Variables ◽  
The Mathematical Model

Abstract In this paper, we demonstrate a probabilistic approach to the design of structures on a cantilever beam with constant load. Individual variables in the mathematical model are not represented deterministically by their specifc values but randomly by probability distributions. Normal distribution is used for all random variables. The resulting probability of failure is calculated using a simple Monte Carlo method, for which a brief overview is also provided in this article. Such a probabilistic proposal is the subject matter of newly emerging feld Reliability of Structures.

Cost-Effective Design Criteria for Australian Monopod Platforms

2003 ◽  
Vol 125 (2) ◽  
pp. 132-138 ◽  
Author(s):  
Rodney Pinna ◽  
Beverley F. Ronalds ◽  
Mark A. Andrich
Keyword(s):  
Structural Reliability ◽  
Cost Benefit ◽  
Cost Effective ◽  
Probability Of Failure ◽  
Structural Failure ◽  
North West ◽  
Number Of Factors ◽  
Suitable Target ◽  
The Cost ◽  
The Relationship

Assessments of structural reliability under storm overload have been performed on various monopod configurations located on Australia’s North West Shelf (NWS). The results have shown that these monopods have lower reliabilities than typical platforms in other petroleum provinces, due to a number of factors. In itself, this may not be a concern, as it may be argued that minimum facilities platforms have relatively low consequences of failure. Reasons for this could center around these monopods being satellites with small production throughput, having short service lives, being not-normally-manned, and having environmental protection features which minimize the possibility of a hydrocarbon spill resulting from a structural failure. A suitable target probability of failure for monopod platforms may be computed using a cost-benefit approach, where the total platform cost, including the cost of failure, is minimized. This analysis is developed for four distinct monopod configurations involving single pile, pile cluster and outrigger foundations in water depths ranging between 9-52m LAT. The relationship between platform CAPEX and probability of failure is derived from first principles for cases of appurtenances located within and external to the main caisson.

The inverse transformation of the explicit fourth-moment standardization for structural reliability

2017 ◽  
Vol 21 (5) ◽  
pp. 769-782 ◽  
Author(s):  
Xuan-Yi Zhang ◽  
Yan-Gang Zhao ◽  
Zhao-Hui Lu
Keyword(s):  
Structural Reliability ◽  
Probability Distributions ◽  
Reliability Assessment ◽  
Random Variables ◽  
Inverse Transformation ◽  
Fourth Moment ◽  
Unknown Probability ◽  
Practical Engineering ◽  
Definition Of ◽  
Skewness And Kurtosis

In practical engineering, the probability distributions of some random variables are often unknown, and the only available information about these may be their statistical moments. To conduct structural reliability assessment without the exclusion of random variables with unknown probability distributions, an explicit fourth-moment standardization function has been proposed, and a single expression of its inverse transformation, that is, normal transformation, with limitations of inputting sets of the third and fourth moments (skewness and kurtosis) of random variables was derived. However, the clear definition of the complete expressions of the inverse transformation of fourth-moment standardization function under different combinations of skewness and kurtosis of random variables has not been provided yet. It is in this regard that four criteria are proposed to derive the complete inverse transformation of fourth-moment standardization function, and then the complete expressions of the inverse transformation are formulated. Through the numerical examples presented, the proposed complete expressions are found to be quite efficient for normal transformations and to be sufficiently accurate to include random variables with unknown probability distributions in structural reliability assessment.

Reliability Based Pressure Containment Uprating

2013 ◽  
Author(s):  
Elie Dib ◽  
Sherif El-Gebaly ◽  
Frank Drennan
Keyword(s):  
Structural Reliability ◽  
Probabilistic Approach ◽  
Probability Of Failure ◽  
Operating Conditions ◽  
Current Status ◽  
Pipeline System ◽  
Design Life ◽  
Target Probability ◽  
Fit For Purpose ◽  
The Cost

Over the design life of long tiebacks, project requirements may change in order to accommodate new prospects. These new prospects may have design conditions exceeding those used for the rest of the field and the existing facilities may not be able to withstand the potential increases in pressure arising from new wells. For smaller and accidental increases, the existing system may be proven to be fit for purpose by using a probabilistic approach, or a structural reliability assessment. This approach may eventually reduce the cost of the new prospect by, for example, removing the need for an over-pressure protection system, or removing the need for a dedicated pipeline system. This paper investigates the potential increase in pressure capacity of a main pipeline for an accidental over-pressure condition using a structural reliability analysis and probabilistic approach using as-built data gathered from several projects. The variations on the as-built pipeline properties, the current status of the existing pipeline, and the corresponding operating conditions are taken into account using a Monte Carlo simulation. The results present a burst pressure with an indication of a safety factor and associated with a probability of failure. A comparison between the final results and the pipeline codes target probability of failure is also performed and presented as part of this paper.

A Comprehensive Approach to Corrosion Management Based on Structural Reliability Methods

2006 ◽  
Author(s):  
Mark Stephens ◽  
Maher Nessim
Keyword(s):  
Structural Reliability ◽  
Failure Modes ◽  
Prediction Models ◽  
Probabilistic Approach ◽  
Corrosion Damage ◽  
Metal Loss ◽  
Corrosion Failure ◽  
Probability Estimates ◽  
Reliability Methods ◽  
Inspection Data

Quantitative analysis approaches based on structural reliability methods are gaining wider acceptance as a basis for assessing pipeline integrity and these methods are ideally suited to managing metal loss corrosion damage as identified through in-line inspection. The essence of this approach is to combine deterministic failure prediction models with in-line inspection data, the physical and operational characteristics of the pipeline, corrosion growth rate projections, and the uncertainties inherent in this information, to estimate the probability of corrosion failure as a function of time. The probability estimates so obtained provide the basis for informed decisions on which defects to repair, when to repair them and when to re-inspect. While much has been written in recent years on these types of analyses, the authors are not aware of any published methods that address all of the factors that can significantly influence the probability estimates obtained from such an analysis. Of particular importance in this context are the uncertainties associated with the reported defect data, the uncertainties associated with the models used to predict failure from this defect data, and the approach used to discriminate between failure by leak and failure by burst. The correct discrimination of failure mode is important because tolerable failure probabilities should depend on the mode of failure, with lower limits being required for burst failures because the consequences of failure are typically orders of magnitude more severe than for leaks. This paper provides an overview of a probabilistic approach to corrosion defect management that addresses the key sources of uncertainty and discriminates between failure modes. This approach can be used to assess corrosion integrity based on in-line inspection data, schedule defect repairs and provide guidance in establishing re-inspection intervals.

scholarly journals Comparative Study of Structural Reliability Assessment Methods for Offshore Wind Turbine Jacket Support Structures

2020 ◽  
Vol 10 (3) ◽  
pp. 860 ◽  
Author(s):  
Abdulhakim Adeoye Shittu ◽  
Ali Mehmanparast ◽  
Lin Wang ◽  
Konstantinos Salonitis ◽  
Athanasios Kolios
Keyword(s):  
Reliability Index ◽  
Structural Reliability ◽  
Reliability Assessment ◽  
Probability Of Failure ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Support Structures ◽  
Structural Components ◽  
Support Structure ◽  
Design Constraints

Offshore wind turbines (OWTs) are deployed in harsh environments often characterized by highly stochastic loads and resistance properties, thus necessitating the need for structural reliability assessment (SRA) to account for such uncertainties systematically. In this work, the SRA of an OWT jacket-type support structure is conducted, applying two stochastic methods to predict the safety level of the structure considering various design constraints. The first method refers to a commercial finite element analysis (FEA) package (DesignXplorer© from ANSYS) which employs direct simulations and the six sigma analysis function applying Latin hypercube sampling (LHS) to predict the probability of failure. The second method develops a non-intrusive formulation which maps the response of the structure through a finite number of simulations to develop a response surface, and then employs first-order reliability methods (FORM) to evaluate the reliability index and, subsequently, the probability of failure. In this analysis, five design constraints were considered: stress, fatigue, deformation, buckling, and vibration. The two methods were applied to a baseline 10-MW OWT jacket-type support structure to identify critical components. The results revealed that, for the inherent stochastic conditions, the structural components can safely withstand such conditions, as the reliability index values were found acceptable when compared with allowable values from design standards. The reliability assessment results revealed that the fatigue performance is the design-driving criterion for structural components of OWT support structures. While there was good agreement in the safety index values predicted by both methods, a limitation of the direct simulation method is in its requirement for a prohibitively large number of simulations to estimate the very low probabilities of failure in the deformation and buckling constraint cases. This limitation can be overcome through the non-intrusive formulation presented in this work.

Cost Effective Minimum Platform Designs Considering Damage Tolerance and Potential Consequences of Failure

2007 ◽  
Author(s):  
Beverley F. Ronalds ◽  
Rodney Pinna ◽  
Geoffrey K. Cole
Keyword(s):  
Structural Reliability ◽  
Damage Tolerance ◽  
Cost Effective ◽  
Probability Of Failure ◽  
Optimal Solutions ◽  
Damage Scenarios ◽  
Reliability Characteristics ◽  
Effective Option ◽  
The Cost

With their simplicity and light structural weight, minimum platforms are a popular solution — even though they may not have the same robustness levels as conventional jackets to withstand extreme or accidental events. These competing attributes are investigated by comparing the cost and structural reliability characteristics of five structures designed using API RP2A. The braced monopod and tripod structures have considerably lower ultimate strengths and residual strengths, and damage scenarios play a much greater role in the overall probability of failure, than for the four-legged jacket. In determining the relative economic merits of the different configurations, the magnitude of the potential consequences of failure becomes an important parameter. Bands of conditional costs of failure for which each structure is the most cost-effective option are derived, with the sturdy monopods and tripod shown to be the optimal solutions for moderate consequence levels.

scholarly journals A Practical Nonprobabilistic Reliability Assessment Method on Key Strata Shear Failure in Longwall Mining

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Hebing Luan ◽  
Jiachen Wang ◽  
Guowei Ma ◽  
Ke Zhang
Keyword(s):  
Structural Reliability ◽  
Shear Failure ◽  
Longwall Mining ◽  
Reliability Assessment ◽  
Friction Angle ◽  
Assessment Method ◽  
Mechanical Tests ◽  
Potential Hazard ◽  
Support Design ◽  
Key Strata

Roof cutting has long been a potential hazard factor in longwall panels in some diggings in China. Meanwhile, the key strata structural reliability, which provides an assessment on the stability of overlying roof strata, may be a significant reference for support design in underground coal mines. This paper aims to investigate a practical nonprobabilistic reliability assessment method on key strata. The mechanical tests and the hollow inclusion triaxial strain tests were conducted to measure relevant mechanical parameters and in situ stress. Furthermore, against the typical failure features in Datong Diggings, China, a shear failure mechanical model of key strata is proposed. Then, an allowable-safety-factor based nonprobabilistic stability probability assessment method is given. The sensitivity of geometrical dimensions and uncertainty levels of friction angle and cohesion are further studied. It is found that thickness and span of key strata have more dominative effect on key strata’s stability compared with the other factor and the increase of uncertainty levels results in decrease of stability probability.

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