Probabilistic Characterization of an Allowable Design Moment in a Piping Elbow

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
Yonghee Ryu ◽  
Abhinav Gupta ◽  
Bu Seog Ju
Keyword(s):  
Nuclear Power ◽  
Stress Index ◽  
Design Equation ◽  
Design Code ◽  
Straight Pipe ◽  
Reliability Level ◽  
Reliability Based Design ◽  
Probabilistic Characterization ◽  
Definition Of

The design of a nuclear power plant piping requires consideration of the effects of pressure and moment loads according to the appropriate design equation, which is Piping design equation (9) in NC/ND-3600, Section III of the ASME Boiler and Pressure Vessel Code. The design moment is influenced significantly by the definition of the B2 stress index in piping elbows. This paper presents a study on reliability-based design for piping elbows on the level D service limit in the design code. Probability density functions (PDFs) of the design moment were calculated using the ASME equation and modified B2 equations. The PDFs of the design moment were evaluated by the collapse moment using the closed-form equations. The probability distribution of the design moment using the modified B2 equation was closer to the distributions of the collapse moment than its design moment using the ASME B2 equation. Probabilistic analyses were conducted to evaluate reliability levels in straight pipe as well as piping elbows using the ASME and modified B2 equations. It was observed that the minimum reliability level (MRL) of the design equation for the straight pipe was slightly higher than the MRL of the elbow. The MRLs of the design equation using the ASME and modified B2 equations were similar for the same values of bend parameter h, and the MRL of the design equation did not show influence of changes in bend parameter, piping type, and B2 stress index.

Fabrication Uncertainty in B2 for Nuclear Pipe Bends Subjected to In-Plane Opening Moment

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
Pronab Roy ◽  
Siddhartha Ghosh
Keyword(s):  
Random Variable ◽  
Nonlinear Finite Element ◽  
Conservative Estimate ◽  
Element Analysis ◽  
Stress Indices ◽  
Primary Stress ◽  
Reliability Based Design ◽  
Probabilistic Characterization ◽  
Geometric Uncertainty

For reliability-based design of pipe bends and elbows, a probabilistic characterization of the primary stress indices (B1 and B2) is essential. This paper aims at the characterization of the fabrication/geometric uncertainty in B2, for thin stainless steel long radius pipe bends, subjected to in-plane opening moment. This characterization is performed in a framework based on Monte Carlo simulation and nonlinear finite element analysis. A revision of the code-based expression for B2 is proposed where a random variable K replaces the constant numerator in this expression. The statistics for K are provided for different pipe nominal dimensions, which indicates that the existing provision gives a very conservative estimate of the plastic collapse moment for pipe bends subjected to in-plane opening flexure.

Evaluation of Allowable External Pressure for Branch Pipe Connections

2012 ◽  
Author(s):  
Kotaro Iwahara ◽  
Kenichi Tachi ◽  
Yoichi Amano ◽  
Katsumasa Miyazaki ◽  
Kiyoharu Tsunokawa
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Branch Pipe ◽  
External Pressure ◽  
Evaluation Procedure ◽  
Outer Diameter ◽  
Design Code ◽  
Straight Pipe ◽  
Element Analysis ◽  
Buckling Strength

Although the allowable external pressure for branch pipe connections is estimated by evaluation procedure for straight pipe, the applicability of procedure for straight pipe to branch pipe connections has not been clear. The applicability of evaluation procedure for straight pipe to branch pipe connections regarding to evaluation of allowable external pressure evaluation was discussed in this study. The buckling pressure of branch pipe connections was estimated by linear eigenvalue analysis with FEA (Finite Element Analysis). The types of branch pipe connections were T-joints and T-pipes. The range of configurations in branch pipe connections for FEA, such as ratio of outer diameter in main to branch pipe D/d and ratio of outer diameter to thickness in main pipe D/T, were determined by survey of branch pipe connections in the Japanese nuclear power plants. The results of the FEA showed that the buckling strength of branch pipe was found sufficiently to be superior than that of straight piping from comparisons of estimations by FEA for branch pipe connections and those by formula for straight pipe in the design code. It was concluded that the formula for straight pipe is applicable for the evaluation of allowable external pressure for branch pipe connections.

scholarly journals Experimental Evaluation of Shear Behavior of Stone Masonry Wall

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2313
Author(s):  
Maria Luisa Beconcini ◽  
Pietro Croce ◽  
Paolo Formichi ◽  
Filippo Landi ◽  
Benedetta Puccini
Keyword(s):  
Shear Behavior ◽  
Stone Masonry ◽  
Masonry Walls ◽  
Mechanical Parameters ◽  
In Situ Tests ◽  
Capacity Curves ◽  
Historical Structures ◽  
Definition Of

The evaluation of the shear behavior of masonry walls is a first fundamental step for the assessment of existing masonry structures in seismic zones. However, due to the complexity of modelling experimental behavior and the wide variety of masonry types characterizing historical structures, the definition of masonry’s mechanical behavior is still a critical issue. Since the possibility to perform in situ tests is very limited and often conflicting with the needs of preservation, the characterization of shear masonry behavior is generally based on reference values of mechanical properties provided in modern structural codes for recurrent masonry categories. In the paper, a combined test procedure for the experimental characterization of masonry mechanical parameters and the assessment of the shear behavior of masonry walls is presented together with the experimental results obtained on three stone masonry walls. The procedure consists of a combination of three different in situ tests to be performed on the investigated wall. First, a single flat jack test is executed to derive the normal compressive stress acting on the wall. Then a double flat jack test is carried out to estimate the elastic modulus. Finally, the proposed shear test is performed to derive the capacity curve and to estimate the shear modulus and the shear strength. The first results obtained in the experimental campaign carried out by the authors confirm the capability of the proposed methodology to assess the masonry mechanical parameters, reducing the uncertainty affecting the definition of capacity curves of walls and consequently the evaluation of seismic vulnerability of the investigated buildings.

Fundamental relations and identities of fuzzy hyperalgebras

2021 ◽  
pp. 1-10
Author(s):  
Narjes Firouzkouhi ◽  
Abbas Amini ◽  
Chun Cheng ◽  
Mehdi Soleymani ◽  
Bijan Davvaz
Keyword(s):  
Universal Algebra ◽  
Equivalence Relation ◽  
Polynomial Function ◽  
Equivalence Relations ◽  
Fundamental Relation ◽  
Term Function ◽  
Biological Phenomena ◽  
Definition Of

Inspired by fuzzy hyperalgebras and fuzzy polynomial function (term function), some homomorphism properties of fundamental relation on fuzzy hyperalgebras are conveyed. The obtained relations of fuzzy hyperalgebra are utilized for certain applications, i.e., biological phenomena and genetics along with some elucidatory examples presenting various aspects of fuzzy hyperalgebras. Then, by considering the definition of identities (weak and strong) as a class of fuzzy polynomial function, the smallest equivalence relation (fundamental relation) is obtained which is an important tool for fuzzy hyperalgebraic systems. Through the characterization of these equivalence relations of a fuzzy hyperalgebra, we assign the smallest equivalence relation α i 1 i 2 ∗ on a fuzzy hyperalgebra via identities where the factor hyperalgebra is a universal algebra. We extend and improve the identities on fuzzy hyperalgebras and characterize the smallest equivalence relation α J ∗ on the set of strong identities.

“Real-World” Microscopy: Understanding Environment-Sensitive Behavior of Ni-Base Welds

1998 ◽  
Vol 4 (S2) ◽  
pp. 528-529
Author(s):  
M. G. Burke ◽  
R. J. Wehrer ◽  
C.M. Brown
Keyword(s):  
Nuclear Power ◽  
Base Alloy ◽  
Analytical Electron Microscopy ◽  
Furnace Cool ◽  
Environmental Embrittlement ◽  
Reported Study ◽  
Compositional Changes ◽  
Insight Into ◽  
Sensitive Behavior

Ni-base alloy welds such as EN82H weld metal are frequently employed in nuclear power applications where resistance to corrosion is required. Results of a recently reported study of the mechanical properties of EN82H welds show that this alloy is susceptible to low-temperature (∼100°C) environmental embrittlement (LTEE) in hydrogenated water. LTEE is a manifestation of hydrogen embrittlement in these alloys.1 Recent LTEE tests have demonstrated a beneficial effect of a high-temperature (∼1100°C) anneal and furnace-cool in alleviating the material's susceptibility to LTEE. Understanding the reason for the reduction in LTEE susceptibility requires detailed characterization of the microstructure so that the specific structural and compositional changes that have been induced by the solution-anneal can be identified. This study reports the results of light optical and analytical electron microscopy (AEM) characterization of the microstructures of as-fabricated and as-solution-annealed EN82H welds with the objective of providing insight into the observed LTEE behavior.

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