Assessing the Target Reliability Index for Nuclear Piping

2016 ◽  
Author(s):  
Kleio Avrithi
Keyword(s):  
Reliability Index ◽  
Historical Data ◽  
Allowable Stress ◽  
Safety Factors ◽  
Code Calibration ◽  
Target Reliability Index ◽  
Consistent Manner ◽  
Factor Design ◽  
Load And Resistance Factor ◽  
Allowable Stress Design

Previous research developed Load and Resistance Factor Design (LRFD) equations for Class 2 and 3 nuclear piping for different reliability levels and load combinations. The LRFD equations consider separate safety factors for each load and for the strength of steel in opposition to the Allowable Stress Design (ASD) equations used in the ASME Boiler and Pressure Vessel (B&PV) Code, Section III, Div. 1, where only one safety factor is considered. In order to use the developed LRFD equations for the design of nuclear piping, specific reliability levels or else acceptable probabilities of failure need to be assigned to each Code equation. The paper discusses the available methods for evaluating the target reliability index, such as historical data of piping failures, expert-opinion elicitation, and Code calibration. Code calibration is the method of determining the existing level of reliability in the Code equations and assigning the same reliability to the developed LRFD equations in a consistent manner. Code Calibration is explained to be the more appropriate method of assigning reliability levels to the LRFD equations. The other methods can supplement the analysis results.

Target Reliability Index for Load and Resistance Factor Design of Class 2 Carbon Steel Pipes

2017 ◽  
Author(s):  
Kleio Avrithi ◽  
Ramiro Mendoza
Keyword(s):  
Carbon Steel ◽  
Internal Pressure ◽  
Reliability Index ◽  
Safety Margin ◽  
Resistance Factor ◽  
Safety Factors ◽  
Target Reliability Index ◽  
Partial Safety Factors ◽  
Factor Design ◽  
Load And Resistance Factor

The use of the Load and Resistance Factor Design (LRFD) for Class 2 nuclear piping can be an alternative of the traditional Allowable Stress Design (ASD) method currently used in the ASME Boiler Pressure Vessel Code, Section III, Div. 1 providing the benefit of a known and consistent reliability for the designed piping. The design uncertainties and the necessary safety margin are evaluated for each equation for all service levels by considering the applied loads (e.g., earthquake, deadweight, internal pressure, etc.) and the resistance of steel, in the form of either the yield or ultimate strength, as separate variables described by their mean value, distribution, and coefficient of variation. The procedure yields different partial safety factors for each load and the resistance in opposition to the one safety factor used in each of the ASD equations of the Code. Although LRFD equations have been developed in the past, a range of possible partial safety factors were assigned to the variables, corresponding to different levels of reliability. This paper discusses the method used, namely calibration, for achieving same reliability as in the Code equations, and the progress made to assess a minimum target reliability index or else acceptable probability of failure for the LRFD equations that consider the earthquake load for pressurized pipes as well as the design for internal pressure for Class 2 nuclear pipes made of carbon steel.

A Reliability-Based Approach for the Design of Nuclear Piping for Internal Pressure

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Kleio Avrithi ◽  
Bilal M. Ayyub
Keyword(s):  
Internal Pressure ◽  
Allowable Stress ◽  
Safety Factors ◽  
Limit States ◽  
Present Design ◽  
Partial Safety Factors ◽  
Factor Design ◽  
American Society ◽  
Load And Resistance Factor ◽  
Allowable Stress Design

Nuclear pipes are designed to withstand primary membrane stresses generated by internal pressure according to the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (B&PV) Code, Section III, Parts NB-3641, NC-3641, and ND-3641, which uses the allowable stress design (ASD) method. This paper presents limit states and equations for the design of nuclear pipes for internal pressure based on the load and resistance factor design (LRFD) method. The LRFD method is shown and explained to be more consistent than the ASD method. The paper presents the procedure for the derivation of the partial safety factors. Moreover, these factors are evaluated, example calculations are provided, and comparisons with the present design are made.

Load and Resistance Factor Design (LRFD) of Nuclear Straight Pipes for Loads That Cause Primary Stress

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Kleio Avrithi ◽  
Bilal M. Ayyub
Keyword(s):  
Resistance Factor ◽  
Safety Factors ◽  
Primary Stress ◽  
Safety Margins ◽  
Division 1 ◽  
Partial Safety Factors ◽  
Factor Design ◽  
Load And Resistance Factor ◽  
Different Levels ◽  
Allowable Stress Design

Class 2 and 3 nuclear piping is designed according to the allowable stress design (ASD) method used in the ASME Boiler and Pressure Vessel (B&PV) code, Sec. III, Division 1, NC and ND-3600 according to which safety factors applied to the strength of steel (resistance) provide acceptable safety margins for the piping design. This paper describes the development of design equations according to the load and resistance factor design (LRFD) method for loads that cause primary stress such as sustained weight, internal pressure, and earthquake for different levels of piping operation. The LRFD method differs from the ASD since multiple factors, applied separately to each load and the strength of steel, provide safety margins that correspond to a known and acceptable probability of failure for the piping. Load combinations are provided, statistical properties for the variables under consideration are presented and the partial safety factors are moreover illustrated for different values of the target reliability index.

Structural Integrity for Nuclear Power Plant Against Excessive Load on Design Extension Condition

2013 ◽  
Author(s):  
Daigo Watanabe ◽  
Kiminobu Hojo
Keyword(s):  
Nuclear Power ◽  
Structural Integrity ◽  
Safety Factors ◽  
Design Code ◽  
Acceptance Criteria ◽  
Integrity Assessment ◽  
Current Design ◽  
Factor Design ◽  
Excessive Load ◽  
Load And Resistance Factor

This paper introduces an example of structural integrity evaluation for Light Water Reactor (LWR) against excessive loads on the Design Extension Condition (DEC). In order to assess the design acceptance level of DEC, three acceptance criteria which are the stress basis limit of the current design code, the strain basis limit of the current design code and the strain basis limit by using Load and Resistance Factor Design (LRFD) method were applied. As a result the allowable stress was increased by changing the acceptance criteria from the stress basis limit to the strain basis limit. It is shown that the practical margin of the LWR’s components still keeps even on DEC by introducing an appropriate criterion for integrity assessment and safety factors.

Application of the Bayesian Updating to the Load and Resistance Factor Design (LRFD) Method

2013 ◽  
Author(s):  
Yuji Nakasone
Keyword(s):  
Reliability Index ◽  
Statistical Data ◽  
Design Method ◽  
Bayesian Updating ◽  
Fracture Probability ◽  
Resistance Factor ◽  
Factor Design ◽  
Index Value ◽  
Load And Resistance Factor ◽  
Adequate Reliability

The present study has attempted to apply the Bayesian updating to the LRFD, or Load and Resistance Factor Design method. The LRFD method takes into account the statistical distribution of the material resistance and those of the applied loads. The LRFD method can reflect the degrees of different uncertainties of the resistances of the materials and the loads. Thus, the LRFD method can attain the optimal design which can keep up an adequate reliability level of the components designed, whereas the conventional allowable stress design (ASD) method cannot. The LFRD method, however, requires vast amount of statistical data for the material resistances and the applied loadings of different kinds. The present study proposes the Bayesian updating scheme which requires only a small amount of statistical data for the material resistance and the various load item distributions to calculate the values of the partial design factors used in the LRFD method. It is revealed that the median of the updated distributions of the estimated standard deviations can give adequate reliability index values higher than the target reliability index value corresponding to a fracture probability of 0.01% even for a small number of the statistical data, say, less than 20. This paper also compares and discusses the LRFD method with the updating scheme and the conventional ASD method, showing that the updated LRFD method can maintain the reliability index value higher than the target index value whereas the ASD method cannot.

Reliability-Based LRFD Criteria for Unstiffened Panel of Ship Structures

2013 ◽  
Author(s):  
Yong Bai ◽  
Miao-hua Qian
Keyword(s):  
Limit State ◽  
State Equation ◽  
Safety Factors ◽  
Ship Structures ◽  
Future Design ◽  
Practical Project ◽  
Safety And Reliability ◽  
Partial Safety Factors ◽  
Factor Design ◽  
Load And Resistance Factor

It is of significance to do the research of safety and reliability for ship structures, especially for marine structures because of the poor conditions and high risks, future design for ship structures will move toward a more rational and probability-based design. This paper chooses the unstiffened panel of ship structures as the research subject. Based on the MATLAB software, this paper develops the procedures and calculates one limit state equation of the panel, derives partial safety factors (PSF) for the Load and Resistance Factor Design (LRFD) of the panel under different reliability index levels. The PSF may provide a reference for the practical project design.

On the Material Properties for Piping Load and Resistance Factor Design

2021 ◽  
Author(s):  
Kleio Avrithi
Keyword(s):  
Reliability Index ◽  
Room Temperature ◽  
Mean Value ◽  
Resistance Factor ◽  
Low Alloy Steel ◽  
Factor Design ◽  
The Mean ◽  
Load And Resistance Factor ◽  
The Impact ◽  
Steel Properties

Abstract The probabilistic properties of steel, namely the mean value, coefficient of variation, and probability distribution are needed for the development of Load and Resistance Factor Design (LRFD) equations for Class 2 and 3 nuclear piping and for probabilistic and risk analysis studies. This work investigates the probabilistic properties for the most representative steels used for nuclear piping, such as carbon, stainless austenitic, and low alloy. Steel properties at room temperature and up to temperature 700oF are examined through reported mechanical behavior. The work concludes with the impact of the stainless steels' probabilistic properties on the reliability index or else probability of failure for the piping. The presented data can help organize steel materials for LRFD and reduce the variability of the reliability index.

nalisis Kuat Tarik Kayu Menggunakan PKKNI 1961 dan SNI 7973:2013

2017 ◽  
Vol 1 (2) ◽  
pp. 63
Author(s):  
Ahmad Hernadi ◽  
Noerman Adi Prasetya ◽  
Rahcmad Aidil
Keyword(s):  
National Standard ◽  
Allowable Stress ◽  
Construction Design ◽  
Wood Construction ◽  
Tension Member ◽  
Factor Design ◽  
Allowable Stress Design

Use of wood construction in Indonesia is decrease significant than concrete and steel. While it is, government by National Standardization Corporation (BSN) had been published Indonesian National Standard about Wood Construction Design Spesification with code SNI 7973:2013. This code absolutly influential the old code which is PKKNI 1961. SNI 7973:2013 is regulate about Load esistance Factor Design (LRFD) and Allowable Stress Design (ASD), while PKKNI 1961 just use ASD method. In case SNI 7973:2013 have been use ASD, but it is different to PKKNI 1961. This research is would to find the different betwen SNI 7973:2013 and PKKNI 1961 to tension member with dimention 5/10, 6/12, 8/12 and 10/10. Result of research to tension member show that LRFD 100%, ASD 65,1% and PKKNI 111,4%.

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