Reliability-Based Design of the Primary Structure of Oil Tankers

1997 ◽  
Vol 119 (4) ◽  
pp. 263-269 ◽  
Author(s):  
G. Casella ◽  
M. Dogliani ◽  
C. Guedes Soares
Keyword(s):  
Reliability Index ◽  
Development Process ◽  
Steel Grade ◽  
Large Scatter ◽  
Reliability Level ◽  
Reliability Based Design ◽  
Longitudinal Strength ◽  
Global Strength ◽  
Oil Tankers ◽  
Oil Tanker

The present paper describes a reliability analysis carried out for two oil tanker-ships having comparable dimensions, but different design. The scope of the analysis was to derive indications on the value of the reliability index obtained for existing, typical and well-designed oil tankers, as well as to apply the tentative “rule checking” formulation developed within the CEC funded SHIPREL Project. The checking formula was adopted to redesign the midships section of one of the considered ships, upgrading her in order to meet the target failure probability considered in the rule development process. The resulting structure, in view of an upgrading of the steel grade in the central part of the deck, leads to a convenient reliability level. The results of the analysis clearly showed that a large scatter exists presently in the design safety levels of ships, even when the Classification Societies’ unified requirements are satisfied. A reliability-based approach for the calibration of the rules for the global strength of ships is therefore proposed, in order to assist designers and Classification Societies in the process of producing ships which are more optimized, with respect to ensured safety levels. Based on the work reported in the paper, the feasibility and usefulness of a reliability-based approach in the development of ship longitudinal strength requirements has been demonstrated.

scholarly journals Efficient optimum safety factor approach for system reliability-based design optimization with application to composite yarns

2019 ◽  
Vol 19 (3) ◽  
pp. 221-230 ◽  
Author(s):  
Gh. Kharmanda ◽  
I. R. Antypas
Keyword(s):  
Design Optimization ◽  
Safety Factor ◽  
Reliability Index ◽  
Performance Measure ◽  
Alternative Methods ◽  
Reliability Based Design Optimization ◽  
Implementation Framework ◽  
Reliability Level ◽  
Reliability Based Design ◽  
Convergence Stability

Introduction. The integration of reliability and optimization concepts seeks to design structures that should be both economic and reliable. This model is called Reliability-Based Design Optimization (RBDO). In fact, the coupling between the mechanical modelling, the reliability analyses and the optimization methods leads to very high computational cost and weak convergence stability. Materials andMethods. Several methods have been developed to overcome these difficulties. The methods called Reliability Index Approach (RIA) and Performance Measure Approach (PMA) are two alternative methods. RIA describes the probabilistic constraint as a reliability index while PMA was proposed by converting the probability measure to a performance measure. An Optimum Safety Factor (OSF) method is proposed to compute safety factors satisfying a required reliability level without demanding additional computing cost for the reliability evaluation. The OSF equations are formulated considering RIA and PMA and extended to multiple failure case.Research Results. Several linear and nonlinear distribution laws are applied to composite yarns studies and then extended to multiple failure modes. It has been shown that the idea of the OSF method is to avoid the reliability constraint evaluation with a particular optimization process.Discussion and Conclusions. The simplified implementation framework of the OSF strategy consists of decoupling the optimization and the reliability analyses. It provides designers with efficient solutions that should be economic satisfying a required reliability level. It is demonstrated that the RBDO compared to OSF has several advantages: small number of optimization variables, good convergence stability, small computing time, satisfaction of the required reliability levels.

Barrier Function Method in Reliability Based Design Optimization

2005 ◽  
Vol 297-300 ◽  
pp. 1882-1887
Author(s):  
Tae Hee Lee ◽  
Jung Hun Yoo
Keyword(s):  
Design Optimization ◽  
Barrier Function ◽  
Reliability Index ◽  
Feasible Solution ◽  
Reliability Based Design Optimization ◽  
User Requirement ◽  
Mean Values ◽  
Reliability Based Design ◽  
Design Variables ◽  
Reliability Method

In practical design applications, most design variables such as thickness, diameter and material properties are not deterministic but stochastic numbers that can be represented by their mean values with variances because of various uncertainties. When the uncertainties related with design variables and manufacturing process are considered in engineering design, the specified reliability of the design can be achieved by using the so-called reliability based design optimization. Reliability based design optimization takes into account the uncertainties in the design in order to meet the user requirement of the specified reliability while seeking optimal solution. Reliability based design optimization of a real system becomes now an emerging technique to achieve reliability, robustness and safety of the design. It is, however, well known that reliability based design optimization can often have so multiple local optima that it cannot converge into the specified reliability. To overcome this difficulty, barrier function approach in reliability based design optimization is proposed in this research and feasible solution with specified reliability index is always provided if a feasible solution is available. To illustrate the proposed formulation, reliability based design optimization of a bracket design is performed. Advanced mean value method and first order reliability method are employed for reliability analysis and their optimization results are compared with reliability index approach based on the accuracy and efficiency.

A New Study on Reliability-Based Design Optimization

1999 ◽  
Vol 121 (4) ◽  
pp. 557-564 ◽  
Author(s):  
J. Tu ◽  
K. K. Choi ◽  
Y. H. Park
Keyword(s):  
Design Optimization ◽  
Reliability Index ◽  
Performance Measure ◽  
Probabilistic Constraints ◽  
Probabilistic Constraint ◽  
Reliability Based Design Optimization ◽  
Performance Measure Approach ◽  
Reliability Based Design ◽  
Index Approach ◽  
Special Cases

This paper presents a general approach for probabilistic constraint evaluation in the reliability-based design optimization (RBDO). Different perspectives of the general approach are consistent in prescribing the probabilistic constraint, where the conventional reliability index approach (RIA) and the proposed performance measure approach (PMA) are identified as two special cases. PMA is shown to be inherently robust and more efficient in evaluating inactive probabilistic constraints, while RIA is more efficient for violated probabilistic constraints. Moreover, RBDO often yields a higher rate of convergence by using PMA, while RIA yields singularity in some cases.

A Modified Reliability Index Approach for Reliability-Based Design Optimization

2009 ◽  
Author(s):  
Po Ting Lin ◽  
Hae Chang Gea ◽  
Yogesh Jaluria
Keyword(s):  
Reliability Index ◽  
Reliability Based Design Optimization ◽  
Convergence Problem ◽  
Analysis Problem ◽  
Numerical Examples ◽  
Reliability Based Design ◽  
Index Approach ◽  
Convergence Problems ◽  
Definition Of ◽  
Performance Constraint

RBDO problems have been intensively studied for many decades. Since Hasofer and Lind defined a measure of the second-moment reliability index, many RBDO methods utilizing the concept of reliability index have been introduced as the Reliability Index Approach (RIA). In the RIA, a reliability analysis problem is formulated to find the reliability index for each performance constraint and the solutions are used to evaluate the failure probability. However, the traditional RIA suffers from inefficiency and convergence problems. In this paper, we revisited the definition of the reliability index and revealed the convergence problem in the traditional RIA. Furthermore, a new definition of the reliability index is proposed to correct this problem and a modified Reliability Index Approach based on this definition is developed. Numerical examples using both the traditional RIA and the modified RIA are compared and discussed.

Comparative Reliability Analysis of FAST-Pipe™ and All-Steel Pipe

2010 ◽  
Author(s):  
Qishi Chen ◽  
Mamdouh M. Salama
Keyword(s):  
New Technology ◽  
High Strength ◽  
Steel Grade ◽  
Steel Pipe ◽  
Conventional Steel ◽  
Reliability Level ◽  
Design Basis ◽  
Steel Technology ◽  
Ongoing Work ◽  
Steel Design

Fiber Augmented Steel Technology Pipe (FAST-Pipe™) is being proposed as an alternative to high strength steel (grade X80 or higher) for high pressure gas transmission pipelines. The FAST-Pipe™ is manufactured by wrapping dry fiberglass on conventional steel pipe. It offers many performance and cost advantages. However, as with any proposed new technology, it is required to achieve a reliability level at least equal to the conventional all-steel technology. This paper summarizes the results of a burst failure probability analysis. It was part of the ongoing work to experimentally and analytically establish the design basis for FAST-Pipe™. The purpose of this study is to estimate the burst failure probabilities of defect-free all-steel and FAST pipes after 30 years of operation, and to identify FAST-Pipe™ design cases which can achieve burst reliability levels comparable to those of an all-steel design. The results of this study suggest that a safety factor of 2.0 on burst pressure is adequate for the FAST-Pipe™.

Practical Reliability-Based Design Approach for Foundation Engineering

1996 ◽  
Vol 1546 (1) ◽  
pp. 94-99 ◽  
Author(s):  
Kok Kwang Phoon ◽  
Fred H. Kulhawy
Keyword(s):  
Research Study ◽  
Limit State ◽  
Drilled Shafts ◽  
Ultimate Limit State ◽  
Foundation Engineering ◽  
Reliability Level ◽  
Reliability Based Design ◽  
Ultimate Limit State Design ◽  
Ultimate Limit ◽  
Selection Of

A research study was completed recently that was directed toward the development of practical, reliability-based design (RBD) equations specifically for foundation engineering. Some of the key RBD principles used in the study are presented. The important considerations involved in the development of practical and robust RBD criteria are emphasized. In particular, the selection of an appropriate reliability assessment technique and the careful characterization and compilation of geotechnical variabilities are important because of their central role in the calculation of the probability of failure and the assessment of the target reliability level. An overview of a simplified RBD approach is given, and an application of this approach to the ultimate limit state design of drilled shafts under undrained uplift loading is discussed.

A Modified Reliability Index Approach for Reliability-Based Design Optimization

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Po Ting Lin ◽  
Hae Chang Gea ◽  
Yogesh Jaluria
Keyword(s):  
Design Optimization ◽  
Reliability Index ◽  
Reliability Based Design Optimization ◽  
Second Moment ◽  
Reliability Indices ◽  
Reliability Based Design ◽  
Design Variables ◽  
Index Approach ◽  
Definition Of ◽  
Code Format

Reliability-based design optimization (RBDO) problems have been intensively studied for many decades. Since Hasofer and Lind [1974, “Exact and Invariant Second-Moment Code Format,” J. Engrg. Mech. Div., 100(EM1), pp. 111–121] defined a measure of the second-moment reliability index, many RBDO methods utilizing the concept of reliability index have been introduced as the reliability index approach (RIA). In the RIA, reliability analysis problems are formulated to find the reliability indices for each performance constraint and the solutions are used to evaluate the failure probability. However, the traditional RIA suffers from inefficiency and convergence problems. In this paper, we revisited the definition of the reliability index and revealed the convergence problem in the traditional RIA. Furthermore, a new definition of the reliability index is proposed to correct this problem and a modified reliability index approach is developed based on this definition. The strategies to solve RBDO problems with non-normally distributed design variables by the modified RIA are also investigated. Numerical examples using both the traditional and modified RIAs are compared and discussed.

Reliability-based design criteria for timber bridges in Ontario

1986 ◽  
Vol 13 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Andrzej S. Nowak ◽  
Raymond J. Taylor
Keyword(s):  
Reliability Index ◽  
Structural Reliability ◽  
Structural Safety ◽  
Design Code ◽  
Bridge Design ◽  
Limit States ◽  
Acceptance Criterion ◽  
Reliability Based Design ◽  
Load And Resistance Factor ◽  
Timber Bridges

The new Ontario Highway Bridge Design Code (OHBDC) is based on limit states theory and therefore uses a load and resistance factor format. This paper deals with the development of the basis for the timber bridge design provisions (OHBDC). Three structural systems are considered: sawn timber stringers, laminated nailed decks, and prestressed laminated decks. The latter system has been successfully used in Ontario for the last 7 years.The acceptance criterion in calculation of load and resistance factors is structural reliability. It is required that bridges designed using the new code must have a reliability equal to or greater than a preselected target value. Reliability is measured in terms of the reliability index. The safety analysis is performed for a structural system rather than for individual members. The live load model was developed on the basis of available truck survey data. Material properties are based on extensive in-grade test results. Numerical examples are included to demonstrate the presented approach. Key words: bridge deck, design code, prestressed timber, reliability, reliability index, stringers, structural safety, timber bridges.

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