Reliability-Based Design of Externally Pressurized Vessels

1998 ◽  
Vol 120 (3) ◽  
pp. 149-153 ◽  
Author(s):  
A. C. Morandi ◽  
P. K. Das ◽  
D. Faulkner
Keyword(s):  
Safety Factor ◽  
Design Procedure ◽  
External Pressure ◽  
Reliability Based Design ◽  
Safety Margins ◽  
Sensitivity Studies ◽  
Pressure Maximum ◽  
Reliability Methods ◽  
Level I ◽  
Future Work

A reliability-based Level I design procedure is proposed for ring-stiffened cylindrical shells under external pressure. The main collapse modes and the present safety factor approach are reviewed. The major aspects involved in code development, such as the statistical properties of the basic variables, reliability methods, sensitivity studies, code format, target reliability, partial safety factor optimization, and comparison with the present practice are described. Safety margins for design are proposed which depend on the design pressure, maximum expected overdive, and shell slenderness. Some suggestions for future work are also given.

A Safety Factor Method for Reliability-Based Component Design

2021 ◽  
pp. 1-34
Author(s):  
Jianhua Yin ◽  
Xiaoping Du
Keyword(s):  
Safety Factor ◽  
Design Method ◽  
Deterministic Component ◽  
Reliability Based Design ◽  
Component Design ◽  
Design Variables ◽  
Wide Range ◽  
Reliability Method ◽  
Reliability Methods ◽  
Input Variables

Abstract Reliability-based design (RBD) identifies design variables that maintain reliability at a required level. For many routine component design jobs, RBD may not be practical as it requires nonlinear optimization and specific reliability methods, especially for those design jobs which are performed manually or with a spreadsheet. This work develops a practical approach to reliability-based component design so that the reliability target can be achieved by conducting traditional component design repeatedly using a deterministic safety factor. The new component design is based on the First Order Reliability Method, which iteratively assigns the safety factor during the design process until the reliability requirement is satisfied. In addition to several iterations of deterministic component design, the other additional work is the calculation of the derivatives of the design margin with respect to the random input variables. The proposed method can be used for a wide range of component design applications. For example, if a deterministic component design is performed manually or with a spreadsheet, so is the reliability-based component design. Three examples are used to demonstrate the practicality of the new design method.

A Practical Safety Factor Method for Reliability-Based Component Design

2020 ◽  
Author(s):  
Jianhua Yin ◽  
Xiaoping Du
Keyword(s):  
Safety Factor ◽  
Design Method ◽  
Deterministic Component ◽  
Reliability Based Design ◽  
Component Design ◽  
Design Variables ◽  
Wide Range ◽  
Reliability Method ◽  
Reliability Methods ◽  
Input Variables

Abstract Reliability-based design (RBD) identifies design variables that maintain reliability at a required level. For many routine component design jobs, RBD may not be practical as it requires nonlinear optimization and specific reliability methods, especially for those design jobs which are performed manually or with a spreadsheet. This work develops a practical approach to reliability-based component design so that the reliability target can be achieved by conducting traditional component design repeatedly using a deterministic safety factor. The new component design is based on the First Order Reliability Method, which iteratively assigns the safety factor during the design process until the reliability requirement is satisfied. In addition to a number of iterations of deterministic component design, the other additional work is the calculation of the derivatives of the design margin with respect to the random input variables. The proposed method can be used for a wide range of component design applications. For example, if a deterministic component design is performed manually or with a spreadsheet, so it the reliability-based component design. Three examples are used to demonstrate the practicality of the new design method.

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.

Stability of negative feedback

2021 ◽  
pp. 377-403
Author(s):  
Geoffrey Brooker
Keyword(s):  
Negative Feedback ◽  
Design Procedure ◽  
Feedback System ◽  
Conditional Stability ◽  
Phase Lag ◽  
Minimum Phase ◽  
Safety Margins ◽  
Nyquist Stability ◽  
Nyquist Plots ◽  
Frequency Dependences

“Stability of negative feedback” discusses the measures that must be taken to guarantee that a negative-feedback system is stable. Examples are given of frequency dependences using Bode and Nyquist plots. Safety margins are quantified by means of gain margins and phase margins; the desirability of a minimum-phase-lag network. A design procedure is formulated. There is discussion of Nyquist (conditional) stability, and how it may be achieved by judicious introduction of a non-linearity. A demonstration circuit shows that these measures can yield Nyquist stability with safety.

scholarly journals Pneumatization Patterns of the Petrous Apex and Lateral Sphenoid Recess

2017 ◽  
Vol 78 (06) ◽  
pp. 441-446 ◽  
Author(s):  
Margherita Bruni ◽  
Robert Wong ◽  
Mark Tabor ◽  
K. Boyev ◽  
Alexander Malone
Keyword(s):  
Sphenoid Sinus ◽  
Normative Data ◽  
Image Guidance ◽  
Pearson Correlation ◽  
Petrous Apex ◽  
Lateral Recess ◽  
Poor Access ◽  
Level I ◽  
Temporal Bones ◽  
Future Work

Introduction The petrous apex poses a challenge for surgical intervention due to poor access. As intraoperative image guidance and surgical instrumentation improve, newer endoscopic approaches are increasingly favored. This study aims to provide normative data on the anatomy of the lateral sphenoid sinus recess and petrous apex. These normative data could assist in determining the efficacy of a transnasal transsphenoidal approach to lesions of the anteroinferior petrous apex. Methods This is a retrospective study investigating normative data on all maxillofacial computed tomography (CT) scans performed at a level I trauma center over a 6-month period. All appropriate images had the pneumatization pattern of the petrous apex and lateral recess of the sphenoid sinus reviewed by a single otologist and graded bilaterally. These were then analyzed in SPSS; Pearson correlation analyses and χ2 test were used. Results A total of 481 patients were identified, yielding a total of 962 temporal bones and sphenoid sinuses for analysis. Eighty-eight percent of sides analyzed had a nonpneumatized lateral recess. The petrous apex was nonpneumatized in 54% of sides analyzed. There was a correlation noted between the degree of pneumatization of the petrous apex and pneumatization of the lateral recess of the sphenoid. Conclusion This study is the first to provide normative data comparing pneumatization of the petrous apex and sphenoid sinus. These data may support future work evaluating the utility of an endonasal approach to the petrous apex.

Reliability Analysis of Cracking and Faulting Prediction in the New Mechanistic–Empirical Pavement Design Procedure

2005 ◽  
Vol 1936 (1) ◽  
pp. 150-160 ◽  
Author(s):  
Michael Darter ◽  
Lev Khazanovich ◽  
Tom Yu ◽  
Jag Mallela
Keyword(s):  
Monte Carlo ◽  
Reliability Analysis ◽  
Design Procedure ◽  
Practical Method ◽  
Pavement Design ◽  
Rigid Pavement ◽  
Pavement Distress ◽  
Reliability Based Design ◽  
Definition Of ◽  
Reliability Performance

Reliability analysis is an important part of the mechanistic–empirical pavement design guide (M-E PDG). Even though mechanistic concepts provide a more accurate and realistic methodology for pavement design, a practical method to consider the uncertainties and variations in design and construction is needed so that a new or rehabilitated pavement can be designed for a desired level of reliability (performance as designed). Several methods, ranging from closed-form approaches to simulation-based methods, can be adopted to perform reliability-based design. However, some methods may be more suitable than others, given the complexities of the design procedure. A formal definition of reliability within the context of the M-E PDG, as well as two reliability analysis approaches considered for incorporation into the design procedure for evaluating the reliability of the rigid pavement design for cracking and faulting, was evaluated. A Monte Carlo–based simulation was combined with the damage accumulation procedure for rigid pavement distress prediction. This approach is recommended for future improvements of the procedure. The development of the reliability analysis procedure implemented into the M-E PDG also was documented. It was demonstrated that although the adopted approach is not as sophisticated as a Monte Carlo–based one, it still represents a step forward compared with AASHTO-93 reliability analysis.

External Cooling: The SWR 1000 Severe Accident Management Strategy

2004 ◽  
Author(s):  
Nikolay Ivanov Kolev
Keyword(s):  
Management Strategy ◽  
External Pressure ◽  
Reactor Vessel ◽  
Severe Accident ◽  
Core Flooding ◽  
External Cooling ◽  
Structural Resistance ◽  
Safety Margins ◽  
Accident Management ◽  
Management Concept

This paper provides the description of the basics behind design features for the severe accident management strategy of the SWR 1000. The hydrogen detonation/deflagration problem is avoided by containment inertization. In-vessel retention of molten core debris via water cooling of the external surface of the reactor vessel is the severe accident management concept of the SWR 1000 passive plant. During postulated bounding severe accidents, the accident management strategy is to flood the reactor cavity with Core Flooding Pool water and to submerge the reactor vessel, thus preventing vessel failure in the SWR 1000. Considerable safety margins have been determined by using state of the art experiment and analysis: regarding (a) strength of the vessel during the melt relocation and its interaction with water; (b) the heat flux at the external vessel wall; (c) the structural resistance of the hot structures during the long term period. Ex-vessel events are prevented by preserving the integrity of the vessel and its penetrations and by assuring positive external pressure at the predominant part of the external vessel in the region of the molten corium pool.

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