bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of ASME XI and BS7910 Allowable Surface Flaw Size Evaluation Procedures in Piping Components
Authors: Kuutti Juha , Oinonen Ahti
Published: November 2018

This paper presents a failure assessment diagram (FAD) and crack size based comparison of the ASME BVPC Section XI Nonmandatory Appendix C and Nonmandatory Appendix H and the British Standard BS 7910:2013 Option 1 assessment methods. The Section XI appendix C evaluates the acceptability of a flaw by determining the expected failure mechanism and by comparing the flaw size with allowable flaw size limits or by comparing the applied stress to the allowable stress. The Section XI appendix H and BS7910 employ a FAD based approach that simultaneously considers brittle fracture, ductile crack extension prior to reaching the limit load and exceedance of the limit load due to the gross plasticity in the cross section. The assessment is performed by calculating the assessment point coordinates and evaluating whether the point is located on the safe side of the FAD line. The three methods are compared for simplified austenitic and ferritic pipes under internal pressure and bending loads with postulated axial and circumferential internal surface flaws. The methods are applied to generate limiting flaw size diagrams for each component under the specified loads. Additionally, the limiting flaw size results are presented in the FAD plots. To maintain comparability between the results, identical input data are used with each analysis approach but using the method-specific formulae.

The performed comparison shows that most often the limiting state is governed by the 75 % flaw depth rule in Section XI article IWB-3640. The largest differences between the methods are observed for cracks with a high length to depth ratio. The difference to the tabulated allowable planar flaws in Article IWB-3514 is typically high. When increasing the applied load to values approaching the limit load, differences in the limiting flaw sizes between the methods are observed, mostly due to the different limit load models and different assumptions on the utilization of the post-yield capacity.

Besides the presented flaw size comparison, the paper presents a quick tool suitable for ranking different piping segments based on failure potential and for quick scoping evaluations of indications found in inspections. The case specific scoping tool is a map of yearly flaw size lines providing the information on which flaw sizes would grow to the final limiting size in a specified timeframe.
Prediction of Erosion Damage in a Choke Valve Working in Severe Slurry Conditions
Authors: Malavasi Stefano , Messa Gianandrea Vittorio , Negri Marco
Published: November 2018

Wellhead choke valves, frequently used to control oil and gas flow rates from producing wells in the petroleum industry, may experience loss of material due to the impingements of solid particles within the extraction fluids. This phenomenon, called impact erosion, is a serious concern to engineers, as it can result in loss of performance or even failure of the devices. Being capable to identify the valve components which are most vulnerable to impact erosion and provide quantitative estimation of the useful life of the chokes under actual production conditions may open the way to improved design and maintenance. The present contribution focuses on the use of Computational Fluid Dynamics techniques for predicting the impact erosion of a choke valve working in severe slurry conditions. The in-house erosion prediction library E-CODE, developed within the authors’ research group and illustrated in previous works, was employed to model the complex phenomena occurring in the valve. The good agreement between the numerical estimates and the outcomes of a test performed in the Hydraulic Laboratory of Politecnico di Milano indicated that, given the composition of the slurry environment and the operation condition of the valve, it is possible to estimate with reasonable accuracy the erosion characteristics of the device. This will allow gathering useful information for improving the scheduled maintenance of the production systems and the design of heavy-duty equipment.
Effect of Nozzle Geometry on the Near-Field Flow Characteristics of High-Pressure Gas Leak Jets
Authors: Li Xiaopeng , Zhuang Fakun , Zhou Rui , Wang Yian , Wang Libo , Xie Guoshan
Published: November 2018

Three-dimensional large eddy simulations of high-pressure jets at the same nozzle pressure ratio of 5.60 but issuing from different nozzles are conducted. Four different nozzle geometries, i.e., the circular, elliptic, square, and rectangular nozzles, are used to investigate the effect of the nozzle geometry on the near-field jet flow behavior. A high-resolution, hexahedral, and block-structured grid containing about 31.8 million computational cells is applied. The compressible flow solver, astroFoam, which is developed based on the OpenFOAM C++ library, is used to perform the simulations. The time-averaged near-field shock structures and the mean axial density are compared with the experiment data to validate the fidelity of the LES results, and the reasonable agreement is observed. The results indicate that the remarkable differences exist in the near-field flow structures of the jets. In particular, the circular and square jets correspond to a three-dimensional helical instability mode, while the elliptic and rectangular jets have a two-dimensional lateral instability in their minor axis planes. A subsonic flow zone exists after the Mach disk in the circular and square jets, but is lacking in the elliptic and rectangular jets. The intercepting shocks in the circular jet originate near the nozzle exit, and appear to be circular in cross-section. The intercepting shocks in the square jet originate at the four corners of the nozzle exit at first, and then are observed along the major axis plane some distance downstream of the nozzle exit. However, the formation of the intercepting shock is observed in the major axis planes but is lacking in the minor axis planes for the elliptic and rectangular jets. In addition, the real mass flow rates and discharge coefficients for different jets are computed based on the LES modeling, and their differences are explored.
Enhanced Seismic Fragility Analysis of Unanchored Above-Ground Steel Liquid Storage Tanks
Authors: Phan Hoang Nam , Paolacci Fabrizio , Alessandri Silvia , Hoang Phuong Hoa
Published: November 2018

Earthquake damage in recent decades has revealed that storage tanks are one of the most vulnerable components in petrochemical and oil processing plants. Damage to tanks commonly associated with losses of containment, and thus results in the overall damage to nearby areas. Many of existing steel storage tanks were designed with outdated analysis methods and with underestimated seismic loads; therefore, various types of failure may occur during a strong ground shaking. This paper aims to present an appropriate methodology for the component fragility evaluation of existing storage tanks in a process plant, which will support for the determination of the loss of containment in terms of the ground motion intensity measure and finally the quantitative risk analysis of the plant and its nearby areas. In this respect, an unanchored oil storage tank, which is ideally located in Sicily (Italy), is selected as a case study. The significance of modeling parameters of the tank is first investigated with a screening study, which is based on nonlinear static pushover analyses of the tank using the ABAQUS software. The study aims to enhance the understanding of which modeling parameters significantly affect the seismic response of the tank and to reduce the number of analyses in the fragility evaluation. The fragility curves are then developed based on a lumped-mass model that is calibrated from the static pushover analysis results. Sources of uncertainty, related to significant parameters previously identified, are considered in the fragility analysis using a sampling procedure to generate statistically significant samples of the model.
Benchmark of Finite Elements and Extended-Finite Elements Methods for Stress Intensity Factors and Crack Propagation
Authors: Lacroix Rémi , Caron Axelle , Dischert Sandrine , Deschanels Hubert , Pignol Moïse
Published: November 2018

Stress intensity factors (SIFs) are a major feature in regulatory analyses of Nuclear Power Plants (NPP) components, as they allow to rule on the acceptability of defects when compared to a critical experimental value (K1c). Simplified and robust evaluations of SIFs have been provided in major regulations standards for cracks having usual geometries and locations in major components.

However, their evaluations still require a significant effort in the case of important deviations of the geometry of cracks regarding the usual semi-elliptical shape, or in the case of specific geometries of components, and specific locations of cracks in components. In these cases, time-consuming Finite Element meshes must be constructed, either manually or using semi-automatical tools, to represent the components and its defect(s). This method can become particularly costly, especially in the case of fatigue crack propagation.

The eXtended-Finite Elements Method (X-FEM) has been proposed to overcome this issue. The representation of the defect is carried out by the level-set method, and specific enrichment functions are used to represent the solution near the crack surface and the crack front.

This paper proposes a benchmark of numerical predictions of stress intensity factors using SYSTUS software [5]. It will be based on:

a) Available analytical solutions;

b) Classical Finite Element method;

c) EXtended-Finite Elements Method.

The classical case of a circular and elliptical crack in a semiinfinite body is first presented. Then the case of a circumferential crack in a valve under a thermo-mechanical loading is analyzed. The accuracy of the different methods is then compared and discussed.
Effect of Static Load Components in Seismic Loading on Gross Plastic Deformation on Structure
Authors: Kai Satoru , Otani Akihito
Published: November 2018

In general, a seismic load acting on a structure is considered to potentially cause unstable gross plastic deformation that is called as plastic collapse, because the seismic load induce an inertia force on the structure which may act as an external force onto the structure. The past researches by the authors to clarify the characteristic of seismic loads found that the way of the seismic response on the structure is driven by the correlation between the seismic loading and the natural frequency of the structure while only the dynamic loads are acting. On the other hand, existence of relatively large sustained loads such as a dead weight was also recognized to promote an unstable gross plastic deformation in the past experimental studies.

Based on the previous studies, two factors that are the sustained load level and the correlation other than the dynamic load level are expected to play an important role in determining the dynamic behavior of a structure and potentially governing the failure mode. The several elastic-plastic analyses with an elastic-perfect-plastic (EPP) material property and a simplified structure were conducted in this paper by slightly changing the level of the sustained loads and the dynamic loads. From the analytical results focusing on the ratchet deformations and residual deformations, the level of the sustained load on the structure was found to promote ratcheting behavior on the structure with a specific trend and significantly affect the dynamic behavior at the conceptual conditions which were defined and identified in the past researches.
Study on the Predictive Evaluation Method of Nonlinear Sloshing Wave Height of Cylindrical Tanks: Part 1 — Shaking Table Test Results and Verification Results of Analytical Method for Nonlinear Sloshing
Authors: Morita Hideyuki , Takata Tomoshige , Madokoro Hideki , Sago Hiromi , Murakami Hisatomo , Yokoi Shinobu , Yamamoto Tomohiko
Published: November 2018

When cylindrical tanks installed on the ground, such as oil tanks and liquid storage tanks, receive strong seismic waves, including the long-period component, motion of the free liquid surface inside the tank called sloshing may occur. If high-amplitude sloshing occurs and the waves collide with the tank roof, it may lead to accidents such as damage to the tank roof or outflow of internal liquid. Therefore, it is important to predict the wave height of sloshing generated by an earthquake input.

Sloshing is vibration of the free liquid surface, and when the sloshing wave height is small, it can be approximated with a linear vibration model. In that case, the velocity-response-spectrum method using velocity potential can estimate the sloshing wave height under an earthquake input. However, when the sloshing wave height increases and the sloshing becomes nonlinear, it is necessary to evaluate the wave height using other methods such as numerical analysis.

Taking into consideration that design earthquake levels tend to increase and the use of seismic isolation mechanisms has continued to spread in recent years, the amplitude of the long-period components of an earthquake input which act on cylindrical tanks may also increase. Therefore, although the evaluation of nonlinear sloshing wave height is important, there are few examples which quantitatively evaluate the wave height of nonlinear sloshing.

The purpose of this study is to construct a simple evaluation technique of a nonlinear sloshing wave height of cylindrical tanks. In this study, the shaking table test using the small cylindrical tank for studying the behavior of nonlinear sloshing was carried out. Furthermore, verification of the flow-analysis technique described by previous report (PVP2017-65313) was carried out by comparing with test results. As a result, the data for constructing an evaluation technique has been acquired. Moreover, the validity of the flow-analysis technique was has been verified.
Numerical Study on the Startup Performance for the High Pressure Inner Casing of the Solar Steam Turbine
Authors: Wang Peng , Chen Gang , Li WenFu
Published: November 2018

Operation flexibility and the high efficiency of thermal cycle are the two hot research topics for the steam turbine unit. For the operation flexibility, it requires the turbine unit be able to start up quickly and frequently, and good thermal fatigue properties of the components are a must. On the other hand, the trend to higher temperature with ultra supercritical (USC) steam is the key drive of ongoing development for the validation of a method to improve the thermal cycle efficiency, but the application of the higher steam temperature will intensify the component’s thermal fatigue.

In this paper, a high pressure inner casing for the new designed solar steam turbine was studied, and the Finite Element Method (FEM) combined with linear elastic material was applied to simulate the transient stress and temperature fields during the daily warm/hot startup process. On the basis of the stress spectrum in the critical zone, the standard DIN EN-12952-3 and the fatigue curve were used to evaluate the low cycle fatigue life consumption in the transient process.
Development of New Design Fatigue Curves in Japan: Discussion of Best-Fit Curves Based on Large-Scale Fatigue Tests of Carbon and Low-Alloy Steel Plates
Authors: Takanashi Masahiro , Ueda Hiroshi , Saito Toshiyuki , Ogawa Takuya , Hayashi Kentaro
Published: November 2018

In Japan, the Design Fatigue Curve (DFC) Phase 1 and Phase 2 subcommittees were organized under the Atomic Energy Research Committee in the Japan Welding Engineering Society and have proposed new design fatigue curves for carbon, low-alloy, and austenitic stainless steels. To confirm the validity of the proposed design fatigue curves, a Japanese utility collaborative project was launched. In this project, fatigue tests were conducted on large-scale and small-sized specimens, and the test data were provided to the DFC Phase 2 subcommittee. This paper discusses the best-fit curves proposed by the DFC Phase 1 subcommittee, focusing on the results of large-scale fatigue tests for carbon steel and low-alloy steel plates. The fatigue test results for large-scale specimens were compared with the best-fit curve proposed by the DFC Phase 1 subcommittee. This comparison revealed that the fatigue lives given by the proposed curves correspond to those of approximately 1.5–4.0-mm-deep crack initiation in large-scale specimens. In this program, fatigue tests with a mean strain were also carried out on large-scale specimens. These tests found that the fatigue lives were almost equivalent to those of approximately 4.4–7.0-mm-deep crack initiation in large-scale specimens. In determining a design fatigue curve, strain-controlled tests are usually performed on small-sized specimens, and the fatigue life is then defined by the 25% load drop. It is reported that the cracks reach nearly 3–4-mm depth under those 25% drop cycles. The test results confirm that the fatigue lives of large-scale specimens agree with those given by the best-fit curve for carbon and low-alloy steels, and no remarkable size effects exist for the crack depths compared in this study.
Investigation of Method of Elasto-Plastic Analysis for Piping System Excited by Multi-Direction Input
Authors: Kabaya Takuro , Kojima Nobuyuki , Arai Masashi , Hirouchi Satoru , Bando Masatsugu
Published: November 2018

This paper provides investigation on method of an elasto-plastic analysis for practical seismic design of nuclear piping systems, which are excited by multi-direction input.

The Japan Society of Mechanical Engineers (JSME) established a task group to develop an elasto-plastic analysis method for nuclear piping systems, and prepared a case example code proposal for JSME.[1],[2] Our studies in past (ASME PVP2016-63186[3] and ASME PVP2017-65341[4]) were implemented on tests with unidirectional excitation using simple piping systems. In order to examine the applicability of the proposed case example code for JSME in piping of actual systems, it is necessary to examine cases in which there is multidirectional input excitation in piping systems in scales comparable to those of the piping in actual systems. We therefore conducted an analytical examination on demonstration of “the ultimate strength of piping system,” which was implemented at NUPEC. [5]

We confirmed in the results of analytical examination that the strain range could be calculated at precision nearly equivalent to our examinations in the past, and that the draft code case was applicable. However, we also found a problem which needs to be solved.

In addition, we were able to confirm that the local damping increase caused by the elasto-plastic behavior of the elbow which was subject to examination in this study was 1% or larger.
Measurement of Natural Frequencies of the Fluid-Elastic-Coupled Shell Plate Vibration of a Large-Sized Cylindrical Steel Tank by Microtremor Observation
Authors: Hatayama Ken , Zama Shinsaku , Yoshida Shoichi
Published: November 2018

We measured the natural frequencies of the fluid-elastic-coupled shell plate vibration excited in a large-sized, flat-bottomed, cylindrical steel tank by observing microtremors at three points of the tank. By comparing the appearance frequencies and the values of the five peaks seen in the observed microtremor spectral ratios of the top or mid-height of the shell plate to the bottom on the tank foundation with the solutions obtained from a fixed-base FEM eigenvalue analysis, we identified the five peaks as belonging to modes (m, n) = (1, 1–5), with m specifying the vertical order and n the circumferential wave number. The measured non-soil-coupled natural frequencies from the spectral ratio agreed fairly well with those obtained from theory using the FEM analysis. The measured frequencies of the fundamental mode (m = n = 1) were also in good agreements with those estimates using a simplified equation assuming a fixed base adopted in seismic codes of the Japanese Fire Service Act. This equation is expected to provide a reliable soil-coupled fundamental-mode natural frequency for a tank resting on firm ground; the storage-soil-coupled effects are presumed to be weak. Without using an FEM analysis, we present a simple approach to determine the non-soil-coupled fundamental-mode natural frequency solely from the observed microtremor spectral ratios. This simplified procedure works very well for the tank examined.
On Categorization of Seismic Load As Primary or Secondary for Piping Systems With Hardening Capacity
Authors: Labbé Pierre B.
Published: November 2018

The concept of primary/secondary categorization is first reviewed and generalized for its application to a non-linear oscillator subjected to a seismic load. Categorizing the seismic load requires calculating the input level associated with the oscillator ultimate capacity and comparing it to the level associated with the plastic yield. To resolve this problem, it is assumed that the non-linear oscillator behaves like a linear equivalent oscillator, with an effective stiffness (or frequency) and an effective damping. However, as it is not a priori possible to predict the equivalent stiffness and damping, a wide range of possibilities is systematically considered. The input motion is represented by its conventional response spectrum.

It turns out that key parameters for categorization are i) the “effective stiffness factor” (varying from 0 for perfect damage behaviour to 1 for elastic-perfectly plastic) and the slope of the response spectrum in the vicinity of the natural frequency of the oscillator. Effective damping and spectrum sensitivity to damping play a second order role. A formula is presented that enables the calculation of the primary part of a seismically induced stress as a function of both the oscillator and input spectrum features. The formula is also presented in the form of a diagram.

This paper follows-up on a similar paper presented by the author at the PVP 2017 Conference [1]. The new development introduced here is that the oscillator exhibits hardening capacity, while no hardening was assumed in [1]. It appears that the conclusions are slightly modified but the trend is very similar to the non-hardening case.

Regarding piping systems, it appears that even when experiencing large plastic strains under beyond design input motions, their observed effective frequency is very close to their natural frequency, decreasing only by a few percents (experimental data from USA, Japan and India are processed). These observations lead to the conclusion that the seismic load, or the seismically induced inertial seismic strains, should basically be regarded as secondary.
Environmental Risk Analysis of Accidental Release From Onshore Oil Pipelines
Authors: Liu Shengli , Liang Yongtu
Published: November 2018

Accidental releases of oil and oil products will cause extensive damage to environment, if timely and effective measures are not available. Predicting the consequences of spilled oil is of significant importance for emergency management. Although software for risk assessment of gas pipelines is very popular, few are available for hazardous liquid pipelines, due to the difference in behaviors of accidental releases of gases and liquids in the same situation. The major differences are that the spread of released oil is mainly affected by the topography of the land and may result in pollution of soil or waterways, while gas pipeline failure may form gas clouds or explosions and merely pose environmental pollution problems. An integrated model was developed in order to analyze the environmental consequences of spills from oil pipelines. The method presented in this paper allowed to predict the flow trajectory of released liquid from a pipeline and other relevant parameters, including the extent of spread of the oil and the proportion of release reaching any important location, such as a river, in any given topography. The methodology has been applied to a release, which occurred in Marshall, Michigan, in 2010. The results obtained are of the correct order of magnitude compared with realistic data. A case-study is presented and discussed to illustrate the features of the methodology. The results confirmed that the proposed model may be considered an important tool within a comprehensive approach to the management of risk related to onshore oil pipelines.
The Simulation of Strong Ground Motion Using Empirical Green Function and Stochastic Method for Southern Taiwan Area
Authors: Teng Tsung-Jen , Chen Pei-Ting , Chang Ting-Wei , Yang Yuan-Sen , Chiu Chien-Kuo , Liao Wen-I
Published: November 2018

This study presents strong ground motion simulation methods for the future fragility study of a power plant in Southern Taiwan. The modified stochastic method and empirical Green function method are utilized to synthesize the strong ground motions of specific events. A modified physical random function model of strong ground motions for specific sites and events is presented in this study with verification of sample level. Based on the special models of the source, path, and local site, the random variables of the physical random function of strong ground motions is obtained. The inverse Fourier transform is used to simulate strong ground motions. For the empirical Green function method, the observed site records from small earthquake events occurring around the source area of a large earthquake are collected to simulate the broadband strong ground motion from a large earthquake event. Finally, an application of proposed two simulated methods of this study for simulating the ground motion records of Nishi-Akashi Station at 1995 Kobe earthquake and 2006 Southern Taiwan PingDong earthquake are presented.
Managing Pressure Equipment Aging in Plants With Major Accident Hazard: A Methodology Satisfying the Requirements of the European Directive 2012/18/UE Seveso III
Authors: Bragatto Paolo , Delle Site Corrado , Milazzo Maria Francesca , Pirone Annalisa , Vallerotonda Maria Rosaria
Published: November 2018

Attention to be paid to the aging of industrial facilities has been growing in the last ten years, both by public authorities and industrial executives. Many process plants, operating in Europe, have reached or exceeded their project nominal life and the safe management of aging is an urgent question. Failures, due to aged chemical process plants, cause the release of hazardous materials with severe consequences for people and workers. To counteract this phenomenon, plant operators carry out many technical activities, including non-destructive controls on piping and vessels, by adopting sophisticated methods (e.g. Risk Based Inspection RBI).

The European Directive 2012/18/UE (Seveso III) for the control of Major Accident Hazard (MAH) introduced a few requirements for the safe aging of critical equipment, which must be verified during mandatory audits. The aim of this work is to present a synthetic methodology that can be useful for both Seveso auditors and industrial managers for evaluating the adequacy of the measures to control the aging of critical equipment.

To achieve a synthetic assessment of the adequacy of the aging management programs, a compensated index method has been developed, which is a simple and easy-to-use tool. The use of an index method inevitably introduces a degree of uncertainty. However, if it is compared to other qualitative methods, such a tool offers the advantage of a major clarity in the assessment process. This paper discusses a practical application of the method within inspection programs, as required by the art. 27 of Seveso III Directive.
Fatigue Life of Welded Joints of AISI 347 Stainless Steel Under Thermomechanical and Variable Amplitude Loading
Authors: Bosch Alexander , Schackert Sophie , Vormwald Michael , Schweizer Christoph
Published: November 2018

The change in operation of conventional power plants — due to the increasing use of renewable energies — from a stationary to a more flexible operation, causes additional stresses to the components by a high amount of smaller load cycles. This fact results in a demand for validated new concepts to estimate fatigue life especially for welded joints which are the weak parts within the piping. Resulting from the measured stains during operation in the LCF regime, a non-linear fracture mechanics based concept was chosen. For the development and validation of the model, different experiment types are carried out using various types of specimens. To consider the influence of different microstructures within a welded component, specimens made of X6CrNiNb18-10 (AISI 347) with the microstructure found in the base material on the one side, and as found in the HAZ on the other side are used. To take the influence of a mechanical and microstructural notch into account, notched specimens of X6CrNiNb18-10 (AISI 347), and welded specimens made of X6CrNiNb18-10 (AISI 347, base material) and X5CrNiNb19-9 (weld material) are used. Experiments are performed with all types of specimens with an increasing complexity from constant amplitude loading to operational loading. The developed nonlinear fracture mechanics based lifetime model uses the effective cyclic J-Integral normalized to the crack length to replace crack growth calculation by a linear damage accumulation. To consider the loading history an algorithm for the calculation of crack opening and crack closure is used. The advantages of this approach are shown by a comparison with damage calculations based on the damage parameter by Smith, Watson and Topper and based solely on the strain ranges. The differences in the concepts will be highlighted and used for further considerations of how to advance the lifetime prediction model for variable amplitudes.

The presented work gives an overview of the preliminary results of the current work on the AiF research project 18842 N ‘Extended damage concepts for thermomechanical loading under variable amplitudes and plastic deformation’.
Finite Element Analysis of Printed Circuit Heat Exchanger Core for High Temperature Creep and Burst Responses
Authors: Mahajan Heramb P. , Devi Urmi , Hassan Tasnim
Published: November 2018

Printed Circuit Heat Exchangers (PCHEs) have high compactness and efficiency for heat transfer, which makes them an attractive option for the Very High Temperature Reactors (VHTRs). Design methodology of PCHE for non-nuclear service is well established in the ASME Code, Section VIII; however, ASME Code rules for PCHE nuclear services are yet to be developed. Towards developing the ASME Section III code rules for PCHE, the study started with the design of PCHE core specimens for testing following the ASME section VIII methodology. The failure responses of these PCHE specimens are investigated by using Finite Elements Analyses (FEA). Two dimensional isothermal plane strain analyses are performed using an uncoupled constitutive material model. Parametric studies by varying shape and size of semicircular channels, PCHE core size, and loading cases are performed to quantify the critical parameters which influence the PCHE failure responses under pressure creep and pressure burst loadings. Results indicate that the maximum creep strain and its location are dependent on the PCHE core size. Significant reduction in creep strains are observed at the channel sharp corners by considering a realistic semielliptical channel shape instead of a semicircular channel in the analysis.
Evaluating Large Aboveground Storage Tanks Subject to Seismic Loading: Part I — Closed-Form Solutions and Equivalent Static Analysis
Authors: Prueter Phillip E. , Kummari Seetha Ramudu
Published: November 2018

Evaluating the dynamic response of large, aboveground storage tanks exposed to seismic loading is multifaceted. There are foundation-structure and fluid-structure interaction effects that can influence the overall tank behavior and likely failure modes. Additionally, local stresses at anchor bolt support chair attachments and the shell-to-floor junction can be difficult to quantify without detailed finite element analysis (FEA). Often times, performing explicit dynamic analysis with liquid sloshing effects can be time consuming, expensive, and even impractical. The intent of this paper is to summarize simplified analysis techniques that can be leveraged to evaluate aboveground storage tanks subject to seismic loading.

Closed-form calculations to establish a recommended design for a tank, including seismic considerations, are available in storage tank design standards, including API 650 [1] (Appendix E). Seismic design standards have evolved significantly in recent years. Furthermore, for many vintage, in-service storage tanks, explicit seismic considerations were not incorporated into the original design. In Part I of this study, these design equations and other closed-form solutions are used to evaluate the structural integrity of a large, in-service, mechanically-anchored storage tank. The design equations in API 650 [1] are used to form the basis of simplified, equivalent static analysis, where seismic loads are applied to a three-dimensional FEA model via equivalent lateral body forces. These practical results are then compared to explicit dynamic seismic behavior of the same tank with fluid-structure interaction effects considered (in Part II of this study [2]). These comparisons offer insight into the appropriateness of using simplified hand-calculations and equivalent static analysis (and their relative conservatism) in lieu of more rigorous explicit dynamic and fluid sloshing simulations.
Ultimate Limit States of Piping Supports With Outer Diagonal Brace Under High Acceleration Sinusoidal Shaking Condition
Authors: Shimazu Ryuya , Sakai Michiya
Published: November 2018

In this study, the fundamental mechanical inelastic behavior of piping supports was investigated in order to consider an effective elastic-plastic evaluation method. High-acceleration vibration tests were conducted using the resonance shaking table installed in Central Research Institute of Electric Power Industry (CRIEPI), and the ultimate limit states of piping supports under vibration conditions were observed. Each specimen had an outer diagonal brace. Buckling or fatigue failure occurred in the vibration test. Fatigue failure did not occur in the static load test. The static and dynamic skeleton curves were in agreement with each other when the failure mode was the same. When the response load did not reach the buckling load in the vibration test, fatigue cracks occurred after the stable response. The locations of the fatigue cracks tended to be where the local buckling occurred in the static tests. In both the vibration and the static load tests, even if the load decreased after the maximum load by buckling, the reaction force of approximately one third of the maximum load was seen, and the reaction force did not become 0 kN.
Fracture Toughness Characterization of Low Upper-Shelf Linde 80 Weld Using Mini-C(T) Specimens
Authors: Ickes Michael R. , Hall J. Brian , Carter Robert G.
Published: November 2018

The Charpy V-notch specimen is the most commonly used specimen geometry in reactor pressure vessel irradiation surveillance programs and there is an extensive stored inventory of irradiated broken Charpy specimens. The advantage of the mini-C(T) (4mm thick C(T)) specimen technique is that multiple specimens can be machined from each half of broken irradiated Charpy specimens. Fracture toughness specimens that can be machined from broken halves of standard Charpy specimens enable the direct measurement of fracture toughness which can be used for engineering evaluation of reactor pressure vessels. Work to validate the mini-C(T) specimens has been performed mostly on unirradiated reactor pressure vessel base and weld metals .

In this study, mini-C(T) specimens were tested providing fracture toughness characterization of an irradiated low upper-shelf Linde 80 weld (WF-70). This weld was utilized in the Midland beltline and has been previously well characterized at ORNL with various types and sizes of fracture toughness specimens. The mini-C(T) specimens were machined from broken previously tested Charpy V-notch size specimens which were irradiated in a material test reactor.

The effect of different methods of measuring the displacement on the results is assessed. The ASTM E1921 results are compared to previous test data produced from larger fracture toughness specimens. In addition, the sensitivity of T0 to the ASTM E1921 censoring value is discussed.
Estimation of Residual Stress Levels in Fitness for Service Evaluations of Linepipe
Authors: Andrews Robert , Slater Simon
Published: November 2018

Codified fitness for service methods such as API 579 or BS 7910 require consideration of residual stresses in fracture assessments, and guidance is given for upper bound residual stress distributions in common weld geometries. However, these distributions are not appropriate for some welding processes currently or historically used in the manufacture of linepipe, such as high frequency induction welding or flash butt welding. In addition, some linepipe manufacturing routes generate large plastic strains which result in high residual forming stresses, or mechanically relax residual stresses generated in earlier stages of production.

This paper first reviews the code recommendations for the effects of plastic strains and stresses from high level pressure testing on residuals stresses. The paper then briefly describes the major methods of producing carbon steel linepipe and provides recommended residual stress levels for the seam weld and parent material of linepipe using the code recommendations. These are based on assumed uniform residual stresses combined with mechanical stress relaxation due to manufacturing steps such as cold expansion and hydrostatic testing. The recommendations are compared with measured residual stress levels from the open literature. Proposals are given for reduced residual stress levels when assessing axial cracks in carbon steel linepipe.
Spatial filters suppress ripple artifacts in the computation of acoustic fields with the angular spectrum method
Authors: Blackmore Joseph , Cleveland Robin O. , Mobley Joel
Published: November 2018

The angular spectrum method (ASM) is an effective tool for propagating wave fields between parallel planes through decomposition of the field into a series of independent plane waves. One source of error is interference from mirror sources introduced through the inherent periodicity of the fast Fourier transform (FFT) used to implement this method numerically. Here, spatial filters attenuate waves propagating at large angles, which are sensitive to mirror sources. Simulations show that this suppresses the ripple artifact whilst preserving the accuracy of the ASM-computed fields. To achieve comparable performance without filtering requires up to a 13.5-fold increase in computation time.
Report Card Grades on the Physical Activity of Children and Youth From 10 Countries With High Human Development Index: Global Matrix 3.0
Authors: González Silvia A. , Barnes Joel D. , Abi Nader Patrick , Susana Andrade Tenesaca Dolores , Brazo-Sayavera Javier , Galaviz Karla I. , Herrera-Cuenca Marianella , Katewongsa Piyawat , López-Taylor Juan , Liu Yang , Mileva Bilyana , María Ochoa Avilés Angélica , Silva Diego Augusto Santos , Saonuam Pairoj , Tremblay Mark S.
Published: November 2018

Background: The Global Matrix 3.0 brings together the Report Card grades for 10 physical activity indicators for children and youth from 49 countries. This study describes and compares the Global Matrix 3.0 findings among 10 countries with high Human Development Index. Methods: Report Cards on physical activity indicators were developed by each country following a harmonized process. Countries informed their Report Cards with the best and most recent evidence available. Indicators were graded using a common grading rubric and benchmarks established by the Active Healthy Kids Global Alliance. A database of grades from the countries was compiled, and letter grades were converted to numerical equivalents. Descriptive statistics and scores for groups of indicators were calculated, and correlation analyses were conducted. Results: Grades for the 10 countries clustered around “D” ranging from “F” to “B+.” Active Transportation had the highest average grade (“C”), whereas Overall Physical Activity had the lowest average grade (“D-”). Low grades were observed for both behavioral and sources of influence indicators. Conclusions: In the context of social and economical changes of high- Human Development Index countries, urgent actions to increase physical activity among children and youth are required. Surveillance and monitoring efforts are required to fill research gaps.
Nonpathogenic Heterologous Prions Can Interfere with Prion Infection in a Strain-Dependent Manner
Authors: Marín-Moreno Alba , Aguilar-Calvo Patricia , Pitarch José Luis , Espinosa Juan Carlos , Torres Juan María
Published: November 2018

As a general conclusion, the outcome of prion coinfection is strongly dependent on the strain combination and the model utilized and is therefore difficult to predict. The coexistence of several prion strains may remain undetected if one of the strains has more favorable conditions to replicate in the host. The use of several models (such as a transgenic mouse expressing PrP from different species) to analyze field prion isolates is recommended to avoid this situation. The inference effect exerted by nonreplicative prion strains should be considered an interesting tool to advance in new therapeutic strategies for treating prion diseases; it may even be a proper therapeutic strategy.
The Chaperone and Redox Properties of CnoX Chaperedoxins Are Tailored to the Proteostatic Needs of Bacterial Species
Authors: Goemans Camille V. , Beaufay François , Arts Isabelle S. , Agrebi Rym , Vertommen Didier , Collet Jean-François
Published: November 2018

How proteins are protected from stress-induced aggregation is a crucial question in biology and a long-standing mystery. While a long series of landmark studies have provided important contributions to our current understanding of the proteostasis network, key fundamental questions remain unsolved. In this study, we show that the intrinsic features of the chaperedoxin CnoX, a folding factor that combines chaperone and redox protective function, have been tailored during evolution to fit to the specific needs of their host. Whereas
Escherichia coli
CnoX needs to be activated by bleach, a powerful oxidant produced by our immune system, its counterpart in
Caulobacter crescentus
, a bacterium living in bleach-free environments, is a constitutive chaperone. In addition, the redox properties of
E. coli
and
C. crescentus
CnoX also differ to best contribute to their respective cellular redox homeostasis. This work demonstrates how proteins from the same family have evolved to meet the needs of their hosts.
The Phosphohistidine Phosphatase SixA Targets a Phosphotransferase System
Authors: Schulte Jane E. , Goulian Mark
Published: November 2018

One common means to regulate protein activity is through phosphorylation. Protein phosphatases exist to reverse this process, returning the protein to the unphosphorylated form. The vast majority of protein phosphatases that have been identified target phosphoserine, phosphotheronine, and phosphotyrosine. A widely conserved phosphohistidine phosphatase was identified in
Escherichia coli
20 years ago but remains relatively understudied. The present work shows that this phosphatase modulates the nitrogen-related phosphotransferase system, a pathway that is regulated by nitrogen and carbon metabolism and affects diverse aspects of bacterial physiology. Until now, there was no known mechanism for removing phosphoryl groups from this pathway.
Salmonella enterica Phylogeny Based on Whole-Genome Sequencing Reveals Two New Clades and Novel Patterns of Horizontally Acquired Genetic Elements
Authors: Worley Jay , Meng Jianghong , Allard Marc W. , Brown Eric W. , Timme Ruth E.
Published: November 2018

Rapid improvements in nucleotide sequencing access and affordability have led to a drastic increase in availability of genetic information. This information will improve the accuracy of molecular descriptions, including serovars, within
S. enterica
. Although the concept of serovars continues to be useful, it may have more significant limitations than previously understood. Furthermore, the discrete absence or presence of specific genes can be an unstable indicator of phylogenetic identity. Whole-genome sequencing provides more rigorous tools for assessing the distributions of these genes. Our phylogenetic and genetic content analyses reveal how active genetic elements are dynamically distributed within a species, allowing us to better understand genetic reservoirs and underlying bacterial evolution.
EEG for the assessment of neurological function in newborn infants immediately after birth
Authors: Finn Daragh , O’Toole John M , Dempsey Eugene M , Boylan Geraldine B
Published: November 2018

Objective

To assess the neurological function of newborn infants in the first minutes after birth using EEG.

Design and patients

We obtained electroencephalography (EEG) recordings in term infants following elective caesarean section. After delivery, disposable EEG electrodes were attached to the infants’ scalp over the frontal and central regions bilaterally and EEG was recorded for 10 min. Both visual and quantitative measures were used to analyse the EEGs.

Setting

The operative delivery theatre of Cork University Maternity Hospital, Ireland.

Results

Forty-nine infants had EEG recordings over the frontal and central regions. The median (IQR) age at time of initial EEG recording was 3.0 (2.5–3.8) min. While movement artefact contaminated parts of many recordings, good-quality EEG, with mixed-frequency activity with a range of 25–50 μV, was observed in all infants. The majority of EEG spectral power was within the delta band: the median (IQR) relative delta power was 87.8% (83.7%–90%). Almost all (95%) spectral power was below a median (IQR) of 7.56 Hz (6.17–9.76 Hz).

Conclusions

EEG recording is very feasible in the immediate newborn period. This study provides valuable objective information about neurological function during this transitional period.