Accepted Manuscripts

James Williams, Addi-Neequie Stone, Ryan Reedy and Ali Gordon
J. Pressure Vessel Technol   doi: 10.1115/1.4042219
Joints gasketed with viscoelastic seals often receive an application of a secondary torque, i.e., re-torque, in order to ensure joint tightness and proper sealing. The importance of understanding gasketed joint behavior under various loading conditions and test parameters is paramount to a successful design. The motivation of this study is to characterize and analytically model the initial and re-torque load relaxation response of a single 25% glass-fiber reinforced polytetrafluorethylene (PTFE) gasket-bolted joint with serrated flange detail by a single set of experimentally determined modeling constants. The Burger-type viscoelastic modeling constants of the material are obtained through optimization from a baseline load relaxation data and compared to a variety of test cases for both initial and re-loadings. Determination of a re-torque parameter, a, allowing modeling constants identified from an initial loading to predict the re-torque relaxation showed the retarded elasticity or K2 term to be most influential in predicting re-torque response. Finally, the validity of the viscoelastic model with the re-torque parameter is shown to reasonably predict re-torque relaxation responses of all test cases investigated.
TOPICS: Torque, Glass, Fibers, Relaxation (Physics), Modeling, Stress, Gaskets, Flanges, Design, Glass fibers, Elasticity, Optimization, Sealing (Process)
Fumio Inada, Michiya Sakai, Ryo Morita, Ichiro Tamura, Shinichi Matsuura, Kiyoshi Saito and Yasuki Ohtori
J. Pressure Vessel Technol   doi: 10.1115/1.4042220
Although acceleration and cumulative absolute velocity (CAV) are used as seismic indexes, their relationship with the damage mechanism is not yet understood. In this paper, a simplified evaluation method for seismic fatigue damage, which can be used as a seismic index for screening, is derived from the stress amplitude obtained from CAV for one cycle in accordance with the velocity criterion in ASME Operation and Maintenance of Nuclear Power Plants 2012, and the linear cumulative damage due to fatigue can be obtained from the linear cumulative damage rule. To verify the performance of the method, the vibration response of a cantilever pipe is calculated for four earthquake waves, and the cumulative fatigue damage is evaluated using the rain flow method. The result is in good agreement with the value obtained by the method based on the relative response. When the response spectrum obtained by the evaluation method is considered, the value obtained by the evaluation method has a peak at the peak frequency of the ground motion, and the value decreases with increasing natural frequency above the peak frequency. A higher peak frequency of the base leads to a higher value obtained by the evaluation method.
TOPICS: Pipelines, Evaluation methods, Fatigue damage, Damage, Nuclear power plant maintenance, Flow (Dynamics), Stress, Waves, Pipes, Vibration, Cantilevers, Cycles, Earthquakes
Kushal Bhattacharyya, Sanjib Acharyya, Sankar Dhar and Jayanta Chattopadhyay
J. Pressure Vessel Technol   doi: 10.1115/1.4042121
In this work variation of the Beremin parameters with temperature for RPV material 20MnMoNi55 steel is studied. Modified Beremin model is used where; strain correction is imposed in the Beremin model formulation. A set of six numbers of tests are performed at a temperature of -110°C in order to determine Reference Temperature (T0) and Master Curve for the entire DBT region as per the ASTM Standard E1921. Monte Carlo simulation is employed to produce a large number of 1T TPB (Three Point Bending specimen) fracture toughness data randomly drawn from the scatter band obtained from the Master curve, at different temperatures of interest in the brittle dominated portion of DBT region to determine Beremin model parameters variation with temperatures
TOPICS: Simulation, Temperature, Steel, Brittleness, Electromagnetic scattering, Fracture toughness, ASTM International
Bowen Liu and Yan Xiangqiao
J. Pressure Vessel Technol   doi: 10.1115/1.4042122
A new method is put forward to predict fatigue life for low cycle non-proportional loading based on the Itoh criterion. The proposed method considers the multiaxiality influence on the reference maximum principal strain path and the calculation of non-proportionality factor Fnp by utilizing a multiaxial fatigue life prediction approach based on the Modified Wöhler Curve Method. Different from the hypothesis of previous integral models for computing factor Fnp where the loading path is considered uniform, a new model using an inhomogeneous integral is presented and a path dependent weight factor is defined to describe this inhomogeneity. The experimental tests of Itoh on 304 stainless steel with 14 different loading cases are referenced to examine the validity of the new method.
TOPICS: Low cycle fatigue, Stainless steel, Fatigue life, Weight (Mass), Cycles
Ying Wu, Sixi Zha and Peng Wei Jin
J. Pressure Vessel Technol   doi: 10.1115/1.4042055
As the debris flow caused by sustained rainfall would cause destructive damage to buried pipeline, the safety of buried pipeline under impact of debris flow draws increasing attention. This paper focuses on the mechanical and deformed behavior of buried pipeline subjected to the debris flow. The effects of relevant parameters are investigated, including the velocity and impact angle of debris flow, massive stone, diameter to thickness ratio of pipeline (D/T) and parameters of corrosion pit (i.e, the depth, length, and width of corrosion pit). A finite model of soil and buried pipeline under the impact of debris flow is established. Multiple regression analysis is implemented to evaluate these influence parameters. The results show that: (1) the velocity and the impact angle of debris flow have a great influence on the pipeline; (2) the massive stone in the debris flow has little effect on the buried pipeline; (3) the internal pressure of the pipeline has an inhibitory effect on the deformation of the pipeline, which can enhance the ultimate bearing velocity of pipeline; (4) D/T determines the ultimate bearing velocity of pipeline. Moreover, the effects of the parameters of corrosion pit on the maximum Von Mises stress are analyzed by multiple regression and ranked as follows: corrosion depth (A)> corrosion length (L) > corrosion width (B). The result may provide effective guidance for the prevention of pipeline against debris flow in mountain area.
TOPICS: Flow (Dynamics), Simulation, Finite element methods, Engineering simulation, Pipelines, Finite element model, Corrosion, Bearings, Pressure, Stress, Deformation, Safety, Regression analysis, Soil, Damage
Guest Editorial  
Oreste S. Bursi, Fabrizio Paolacci and Tomoyo Taniguchi
J. Pressure Vessel Technol   doi: 10.1115/1.4041284
The scientific community is currently paying particular attention on the effects of Na-Tech events to industrial facilities for the important economic and social impact that these events can entail on the society. In fact, effective risk analysis is critical for industrial plants to assure the necessary safety level as clearly demonstrated by very recent events as the 2011 Tohoku Earthquake. Nevertheless, the effort in developing new techniques is being more and more important as clearly proven by the rapid increasing of the contributions on this topic. This special topic, titled "Na-tech risk assessment methodologies and mitigation solutions in the process industries", promoted by the Guest Editors: Oreste S. Bursi, Fabrizio Paolacci and Tomoyo Taniguchi, within the Seismic Engineering Technical Committee of the ASME Pressure Vessel and Piping Division, is aimed to bring together the latest methodologies and techniques for a reliable estimation of Na-Tech risk in process plants that represents one of the most diffused hazards in industrial facilities. Contributions were called from researchers and industry professionals, strongly active in this area. A total of ten papers were accepted that cover many of the key topics related to Na-Tech events and consequences in Industrial Facilities.
TOPICS: Safety, Pressure vessels, Earthquake engineering, Pipes, Process industries, Risk analysis, Earthquakes, Industrial plants, Risk assessment, Risk, Hazards
Roberto Javier Merino Vela, Emanuele Brunesi and Roberto Nascimbene
J. Pressure Vessel Technol   doi: 10.1115/1.4041285
Non-structural components play an important role in the correct functioning of industrial facilities, which may suffer greatly from earthquake-induced actions, as demonstrated by past seismic events. Therefore, the correct evaluation of seismic demands acting upon them is of utmost importance when assessing or designing an industrial complex exposed to seismic hazard. Among others, nonlinear time history analyses of structural systems including non-structural elements and floor response spectra are well-known methods for computing these actions, the former being more accurate and the latter being less onerous. This work focuses on deriving floor spectra for a steel special concentrically braced frame (SCBF), which is a common type of lateral-load resisting system for industrial frames. The results are used to compute the seismic actions on a small liquid storage tank mounted on the case study frame. Additionally, the results are compared to those obtained by modeling the structure and the tank together. A simple model, consisting of two uncoupled single degree of freedom systems, is used to represent the tank. The floor spectra resulting from both models are compared to establish differences in the behavior of the structure and non-structural element/component. Finally, the seismic demand on the tank - obtained by direct and indirect analyses - is compared to that obtained by applying ASCE 7-10 and Eurocode 8 prescriptions.
TOPICS: Spectra (Spectroscopy), Earthquakes, Storage tanks, Earthquake risk, Steel, Stress, Degrees of freedom, Design, Modeling
Caputo Antonio C., Paolacci Fabrizio, Bursi Oreste S. and Giannini Renato
J. Pressure Vessel Technol   doi: 10.1115/1.4040804
Earthquakes represent a class of natural-technical (NaTech) hazards which in the past have been responsible of major accidents and significant losses in many industrial sites. However, while codes and standards are issued to design specific structures and equipment in the civil and industrial domain, established procedures for seismic quantitative risk assessment (QRA) of process plants are not yet available. In this paper, a critical review of seismic QRA methods applicable to process plants is carried out. Their limitations are highlighted and areas where further research is needed are identified.
TOPICS: Engineering standards, Accidents, Design, Decision making, Earthquakes, Risk assessment, Hazards, Chemical processes
Valerio De Biagi, Bernardino Chiaia, Luca Fiorentini and Cristina Zannini-Quirini
J. Pressure Vessel Technol   doi: 10.1115/1.4040313
Seismic hazard represents one of the possible triggering causes for NaTech accidents in refineries and production plants. The vulnerability of steel storage tanks was evaluated within the framework of a rapid risk assessment. This paper reports the results of the investigation. The outputs of the analysis are plotted on normalized axes and trends among the results are observed. Finally, a comparison between the criticalities and the fragility curves found in the literature is proposed
TOPICS: Steel, Accidents, Risk assessment, Storage tanks, Risk, Earthquake risk
Mohamed Fersi and Ali Triki
J. Pressure Vessel Technol   doi: 10.1115/1.4040136
This paper explored and compared the effectiveness of the inline and the branching re-design strategies used to control water-hammer surges initiated into an existing steel piping systems. The piping system is handled, at its transient sensitive regions, by replacing an inline, or adding a branching, short-section made of high- or low-density polyethylene pipe-wall materials. The Ramos model was used to describe the transient flow, along with the Method of Characteristics implemented for numerical computations. The comparison of the numerical solution with experimental data available from the literature and alternative numerical solution evidenced that the proposed model could reproduce satisfactorily the magnitude and the phase shift of pressure head evolution. Further, the robustness of the proposed protection procedures was tested with regard to water-hammer up- and down-surge mechanisms, taken separately. Results demonstrated that both utilized techniques provided a useful tool to soften both water-hammer up- and down-surges. Additionally, the amortization of pressure-head -rise and -drop was sensitive to the short-section material and size. Moreover, the branching strategy illustrated several enhancements to the inline one in terms of period spread-out limitation, while providing acceptable pressure-head damping.
TOPICS: Water hammer, Design, Pipes, Pressure, Surges, Piping systems, Robustness, Unsteady flow, Steel, Low density polyethylene, Phase shift, Transients (Dynamics), Computation, Damping
Marta D'Amico and Nicola Buratti
J. Pressure Vessel Technol   doi: 10.1115/1.4040137
The evaluation of seismic vulnerability of atmospheric on-grade steel storage tanks is a fundamental topic in the context of industrial safety. Depending on the shell portion affected, on the extent of damage and on toxicity, flammability and reactivity of stored substances, liquid leakages can trigger hazardous chains of events whose consequences affect not only the plant but also the surrounding environment. In light of that, the study proposed herein provides an analysis of the seismic fragility of cylindrical on-grade storage tanks, based on observational damage data. The first phase of this work has consisted in collecting a large empirical dataset of information on failures of atmospheric tanks during past earthquakes. Two sets of Damage States have then been used in order to characterize the severity of damage and the intensity of liquid releases. Empirical fragility curves has been fitted by using Bayesian regression. The advantage of this approach is that it is well suited to treat direct and indirect information obtained from field observations and to incorporate subjective engineering judgement. Different models have been employed in order to investigate the effects of tank aspect ratio, filling level and base anchorage. Moreover, the effects of interaction between these critical aspects is included in fragility analysis. The hazard parameter used is the Peak Ground Acceleration. Seismic Fragility curves obtained from the described procedure are compared to those available in the technical literature.
TOPICS: Steel, Damage, Storage tanks, Hazards, Safety, Anchorage, Chain, Earthquakes, Failure, Shells, Leakage
Akira Maekawa and Tsuneo Takahashi
J. Pressure Vessel Technol   doi: 10.1115/1.4039697
This study describes inelastic seismic design of piping systems considering the damping effect caused by elastic-plastic property of a pipe support which is called an elastic-plastic support. Though the elastic-plastic support is proposed as inelastic seismic design framework in the Japan Electric Association code for the seismic design of nuclear power plants (JEAC4601), the seismic responses of the various piping systems with the support are unclear. In this study, the damping coefficient of a piping system is focused on, and the relation between seismic response of the piping system and elastic-plastic behavior of the elastic-plastic support was investigated using nonlinear time history analysis and complex eigenvalue analysis. The analysis results showed that the maximum seismic response acceleration of the piping system decreased largely in the area surrounded by pipe elbows including the elastic-plastic support which allowed plastic deformation. The modal damping coefficient increased a maximum of about seven-fold. Furthermore, the amount of the initial stiffness of the elastic-plastic support made a difference in the increasing tendency of the modal damping coefficient. From the viewpoint of the support model in the inelastic seismic design, the reduction behavior for the seismic response of the piping system was little affected by the 10% variation of the secondary stiffness. These results demonstrated the elastic-plastic support is a useful inelastic seismic design of piping systems on the conditions where the design seismic load is exceeded extremely.
TOPICS: Earthquake resistant design, Damping, Pipes, Piping systems, Stiffness, Eigenvalues, Nuclear power stations, Design, Stress, Deformation
Hoang Nam Phan, Fabrizio Paolacci and Silvia Alessandri
J. Pressure Vessel Technol   doi: 10.1115/1.4039635
Catastrophic failure of above ground storage tanks was observed during past earthquakes, which caused serious economic and environmental consequences. Many of the existing steel storage tanks were designed with outdated analysis methods and underestimated seismic loads. Therefore, the assessment of their seismic vulnerability is extremely important. Fragility functions are useful tools to quantify the seismic vulnerability of structures in the framework of probabilistic risk assessment. They give the probability that a seismic demand on a structural component exceeds its capacity. The objective of this study is to examine the seismic vulnerability of an unanchored steel storage tank based on the fragility analysis, considering both aleatoric and epistemic uncertainties. The significance of uncertain modeling parameters, attributed to the epistemic uncertainty, is first investigated with a screening study, which is based on nonlinear pushover analyses of the tank using the ABAQUS software. In this respect, a fractional factorial design and ANOVA technique have been adopted. The results indicated that the considered modeling parameters have a significant effect on the uplift behavior of the tank. The fragility curves are then developed based on a simplified model, where the uplift behavior is modeled based on static pushover analysis. Sources of uncertainty, associated with the significant parameters previously identified and the ground motion, are considered in the fragility analysis using a sampling procedure to generate statistically significant samples of the model. The relative importance of ground motion and modeling parameter uncertainties on the fragility curves of the tank is assessed and discussed in detail.
TOPICS: Steel, Modeling, Storage tanks, Accounting, Uncertainty, Probabilistic risk assessment, Computer software, Earthquakes, Failure, Probability, Structural elements (Construction), Stress, Design
Konstantinos Bakalis, Athanasia Kazantzi, Dimitrios Vamvatsikos and Michalis Fragiadakis
J. Pressure Vessel Technol   doi: 10.1115/1.4039634
A simplified approach is presented for the seismic performance assessment of liquid storage tanks. The proposed methodology relies on a nonlinear static analysis, in conjunction with suitable 'strength ratio-ductility-period' relationships, to derive the associated structural demand for the desired range of seismic intensities. In absence of available relationships that are deemed fit to represent the nonlinear-elastic response of liquid storage tanks, several Incremental Dynamic Analyses are performed for variable post-yield hardening ratios and periods in order to form a set of data that enables the fitting of the response. Following the identification of common modes of failure such as elephant's foot buckling, base plate plastic rotation and sloshing wave damage, the aforementioned relationships are employed to derive the 16%, 50% and 84% percentiles for each of the respective response parameters. Fragility curves are extracted for the considered failure modes, taking special care to appropriately quantify both the median and the dispersion of capacity and demand. A comparison with the corresponding results of Incremental Dynamic Analysis reveals that the pushover approach offers a reasonable agreement for the majority of failure modes and limit states considered.
TOPICS: Performance evaluation, Storage tanks, Dynamic analysis, Failure mechanisms, Buckling, Failure, Fittings, Rotation, Hardening, Waves, Ductility, Damage, Sloshing
Shuangmiao Zhai, Shaoping Zhou, Shaojie Chen, Bin Yang and Yong Li
J. Pressure Vessel Technol   doi: 10.1115/1.4039502
Pressure vessel plays an increasingly important role in process industries, in which its performance degradation, such as crack and corrosion, may lead to serious accidents and significant economic losses. Guided wave-based method is a cost-effective means for pressure vessel rapid interrogation. In this paper, direct-wave and fuzzy C-means clustering algorithm (FCM) are used to locate defect for pressure vessel. Finite element (FE) simulation is applied to analyze the propagation characteristics of guided waves. The experiment using the method based on direct-wave and FCM has been conducted on the barrel and head with different sensor arrays respectively. The variation rule of the direct-wave difference with different distance coefficients has been studied. By combination of the FCM, the defects on barrel and head can be detected accurately. The defect inspection experiment for pressure vessel using ellipse imaging algorithm is conducted as well. The experimental results show that the method based on direct-wave and FCM can locate the defects on barrel and head of pressure vessel effectively and accurately.
TOPICS: Pressure vessels, Waves, Algorithms, Corrosion, Finite element analysis, Process industries, Imaging, Simulation, Sensors, Inspection, Fracture (Materials), Accidents
Yonghee Ryu, Abhinav Gupta and Ju Bu Seog
J. Pressure Vessel Technol   doi: 10.1115/1.4039004
Many studies assessing the damage from 1971 San Fernando and 1994 North Ridge earthquakes reported that the failure of non-structural components like piping systems was one of the significant reasons for shutdown of hospitals immediately after the earthquakes. This paper is focused on evaluating seismic fragility of a large-scale piping system in representative high-rise, mid-rise, and low-rise buildings using nonlinear time history analyses. The emphasis is on evaluating piping's interaction with building and its effect on piping fragility. The building models include the effects of nonlinearity in the performance of beams and columns. In the 20-story building that is detuned with the piping system, critical locations are on the top two floors for the linear frame building model. For the nonlinear building model, critical locations are on the bottom two floors. In the 8-story building that is nearly tuned with the piping system, the critical locations for both the linear frame and nonlinear models are the 3rd and 4th floors. It is observed that building nonlinearity can reduce fragility due to reduction in the tuning between building and piping systems. In the 2-story building, the nonlinear building frequencies are closer to the critical piping system frequencies than the linear building frequency; the nonlinear building is more fragile than the linear building for this case. However, it is observed that the linear building models give excessively conservative estimates of fragility than the nonlinear building models.
TOPICS: Structures, Pipes, Piping systems, Earthquakes, Failure, Damage
Xu Liang, Zeng Cao, Hongyue Sun, Xing Zha and Jianxing Leng
J. Pressure Vessel Technol   doi: 10.1115/1.4038724
An analytical method and a semi-analytical method are proposed to analyze the dynamic thermo-elastic behavior of structures resting on a Pasternak foundation. The analytical method employs a finite Fourier integral transform and its inversion, as well as a Laplace transform and its numerical inversion. The semi-analytical method employs the state space method, the differential quadrature method (DQM) and the numerical inversion of the Laplace transform. To demonstrate the two methods, a simply-supported Euler-Bernoulli beam of variable length is considered. The governing equations of the beam are derived using Hamilton's principle. A comparison between the results of analytical method and the results of semi-analytical method is carried out, and it is shown that the results of the two methods generally agree with each other, sometimes almost perfectly. A comparison of natural frequencies between the semi-analytical method and the experimental data from relevant literature shows good agreements between the two kinds of results, and and the semi-analytical method is validated. Different numbers of sampling points along the axial direction are used to carry out convergence study. It is found that the semi-analytical method converges rapidly. The effects of different beam lengths and heights, thermal stress, and the spring and shear coefficients of the Pasternak medium are also investigated. The results obtained in this paper can serve as benchmark in further research.
TOPICS: Thermoelasticity, Laplace transforms, Springs, Shear (Mechanics), Thermal stresses, Hamilton's principle
Technology Review  
Kyle Gough and Daniel Peters
J. Pressure Vessel Technol   doi: 10.1115/1.4037197
Layered vessels have been in-service for many years which use layered construction. This construction technique has been employed since the 1930's. This generally involved either concentric plates or spirally wrapped plates to manufacture vessels with thick walls that otherwise would require very thick and heavy forgings. Long term asset management of these vessels, including non-destructive evaluation of the vessels welds and life assessment of the vessels due to operational cycling the vessels experience can be challenging. This paper is meant to address some of the challenges in managing these critical assets and provide a discussion on the application of state of the art techniques which are being applied today.
TOPICS: Design, Vessels, Fitness-for-service, Plates (structures), Construction, Nondestructive evaluation, Forgings (Products), Welded joints

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