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Accepted Manuscripts

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research-article  
James E. Laurinat and Steve J. Hensel
J. Pressure Vessel Technol   doi: 10.1115/1.4041688
A resin slurry venting analysis was conducted to address safety issues associated with over-pressurization of ion exchange columns used in the plutonium uranium redox extraction (PUREX) process at the U. S. Department of Energy's (DOE's) Savannah River Site (SRS). If flow to these columns were inadvertently interrupted, an exothermic runaway reaction could occur between the ion exchange resin and the nitric acid used in the feed stream. This reaction generates significant quantities of non-condensable gases. To prevent the column from rupturing due to pressurization by these gases, rupture disks are installed on the column vent lines. The venting analysis models accelerating rate calorimeter (ARC) tests and data from tests that were performed in a vented test vessel with a rupture disk. The tests showed that the pressure inside the test vessel continued to increase after the rupture disk opened, though at a slower rate than prior to the rupture. The increase in the vessel pressure is modeled as a transient phenomenon associated with expansion of the resin slurry/gas mixture upon rupture of the disk. It is postulated that the maximum pressure at the end of this expansion is limited by energy minimization to approximately 1.5 times the rupture disk burst pressure. The magnitude of this pressure increase is consistent with the measured pressure transients. The results of this analysis demonstrate the need to allow for a margin between the design pressure and the rupture disk burst pressure in similar applications.
TOPICS: Slurries, Resins, Pressure, Rupture, Disks, Vessels, Transients (Dynamics), Ion exchange, Gases, Safety, Flow (Dynamics), Design, Energy conservation, Rivers, Uranium, Vents
research-article  
Elizabeth S Drexler, Robert Amaro, Andrew J. Slifka, Peter Bradley and Damian S Lauria
J. Pressure Vessel Technol   doi: 10.1115/1.4041689
The economical and efficient transportation of hydrogen gas is necessary for it to become a widespread source of energy. One way to improve the economics is to lower the cost of building hydrogen gas pipelines. The recent modification to the ASME B31.12 Code for Hydrogen Piping and Pipelines begins to lower the cost of building pipelines for hydrogen service by allowing the use of high-strength steel that will provide the same margin of safety with thinner pipe walls. Less steel directly impacts the cost of materials and welding. A means of improving efficiency would be to increase the hydrogen gas pressure to augment the volume of products transmitted through the pipeline. The recent B31.12 code modification characterized dozens of fatigue crack growth test results conducted in hydrogen gas pressurized up to 21 MPa with an upper boundary to the combined datasets. In this study, different pipe geometries, strengths, and pressures with established design protocols were evaluated to determine if the code would require further modifications should linepipes be designed for higher hydrogen gas pressures, up to 34 MPa. It was shown through a numerical exercise that the code could be minimally modified and safety margins would be adequate for those pressures for steels up to and including API-5L Grade X70.
TOPICS: Pipelines, Hydrogen, Pipes, Safety, Steel, Welding, Diluents, American Petroleum Institute, Pressure, High strength steel, Pipeline construction, Design, Economics , Transportation systems, Fatigue cracks
research-article  
Shijun Wu, Keren Xie, Canjun Yang and Dejun Li
J. Pressure Vessel Technol   doi: 10.1115/1.4041488
In this paper, a novel visual experimental apparatus for simulating seafloor hydrothermal venting is proposed. The instrument consists mainly of an acrylic pressure vessel and a hydrothermal fluid syringe pump, which provided a 360º view of the simulated hydrothermal venting and plumes. Theoretical calculation and finite-element analysis were conducted to demonstrate the appropriateness of material selection and structural design for the acrylic pressure vessel. The experimental apparatus was tested at elevated temperature and pressure of up to 300ºC and 12 MPa. Hydrothermal venting experiments were successfully carried out with this apparatus, and clear images of hydrothermal plumes were obtained.
TOPICS: Simulation, Seabed, Pressure vessels, Plumes (Fluid dynamics), Finite element analysis, Instrumentation, Pumps, Pressure, Temperature, Fluids, Structural design
research-article  
Roberto Cipollone, Fabio Fatigati and Davide Di Battista
J. Pressure Vessel Technol   doi: 10.1115/1.4041489
Hydraulic accumulators are vessels charged with inert gas used to store pressurized fluid to actuate specific functions. In particular, they are widely used for remote functions control, as in deep water drilling. In this sector, they assume a fundamental importance because they are responsible of the actuation of the Blowout Preventer valves (BOP), which have to be intrinsically safe and reliable. A Direct Method for the design of the subsea rapid discharge accumulators was presented in this paper and compared with the API 16D Method C, which is the most important international standard concerning the accumulators sizing. The design done according to the regulation insures that the entire volume required by all the functions will be delivered at least at the minimum operating pressure of the last function. Nevertheless, intermediate actuations require also minimum pressure levels above which the actuating fluid should be kept: this requirement is mandatory to fulfill the actuation. The Direct Method presented is based on a fully mathematical model of the charging and discharging phases allowing the evaluation of the pressure inside the accumulators during all the actuations. Having based the design on the physical representation of the processes, the influence of the operating conditions is discussed as well as the combined effect of thermal uncertainties, which are generally unavoidable on site. A specific "failure plane" has been presented to put in evidence, in a sequence of three actuations, which one of them fails for a specific couple of data of subsea and surface temperatures.
TOPICS: Ocean engineering, Design, Secondary cells, Vessels, Pressure, Fluids, Underwater drilling, Engineering standards, Hydraulic accumulators, Valves, Failure, Temperature, Uncertainty, American Petroleum Institute
research-article  
Takahiro Hayashi
J. Pressure Vessel Technol   doi: 10.1115/1.4041433
Pipe inspection is generally executed with ultrasonic pulse echo testing where a small range of pipe wall under an ultrasonic transducer can be evaluated in one measurement. Costly and laborious point-by-point testing is required if a whole range of a pipe should be inspected. The author has investigated fast defect imaging for a plate-like structure using a scanning laser source (SLS) technique as an efficient defect inspection technique. Although the imaging technique is feasible in non-contact remote measurements, only a plate cross-section under the laser irradiation surface can be evaluated. This study describes detection of wall thinning on the back of a pipe using resonance of guided wave propagating in a pipe circumference by non-contact remote measurements with the SLS technique. The narrowband elastic waves are generated in a pipe by modulating laser pulses with fiber laser equipment. When the modulation frequency is in harmony with the resonance frequency of a circumferential guided wave, the distribution of the frequency spectrum peak obtained with the SLS technique become identical to the resonance pattern of the circumferentially guided wave mode. The distributions are distorted for a pipe with wall thinning on the back indicating that this technique has a potential for detection of defects on the back of a pipe.
TOPICS: Pipes, Resonance, Lasers, Waves, Imaging, Inspection, Testing, Fiber lasers, Ultrasonic transducers, Irradiation (Radiation exposure), Elastic waves, Echoes
research-article  
Pierre Dulieu, Valery Lacroix and Kunio Hasegawa
J. Pressure Vessel Technol   doi: 10.1115/1.4041435
If a single subsurface flaw is detected that is close to the component free surface, a flaw-to-surface proximity rule is used to determine whether the flaw should be treated as a subsurface flaw, or transformed to a surface flaw. The transformation from subsurface to surface flaw is adopted as flaw-to-surface proximity rules in all fitness-for-service (FFS) codes. These proximity rules are used under the condition of the component free surface without stress concentration. On the other hand, subsurface flaws have been found under the notches, such as roots of bolts, toes in welded joints or geometrical discontinuities of components. The stress intensity factors of the subsurface flaws are affected by the stress concentrations caused by the notches. The interaction of stress intensity factor increases with increasing stress concentration factor and decreasing the ligament distance between the tips of the subsurface flaws and the notches for a given notch width. Such subsurface flaws shall be transformed to surface flaws at far distance of the notch tips for conservative evaluations. This paper shows the interactions of stress intensity factors of subsurface flaws under stress concentration fields. Based on the interaction, a flaw-to-surface proximity criterion for a circular flaw is proposed under the stress concentration field induced by a notch.
TOPICS: Stress, Stress concentration, Fitness-for-service, Welded joints
Technical Brief  
Zheng Liang, Yao Xiao and Jie Zhang
J. Pressure Vessel Technol   doi: 10.1115/1.4041434
A numerical simulation method is adopted to analyze the effects of above three types of defect geometries ((1) a single defect on the inner surface, (2) a single defect on the outer surface, and (3) double coaxial defects on the inner surface and the outer surface.) on the residual strength of corroded X60 steel pipes and equivalent stress and plastic strain distribution of the local defect area. The results show the defect geometry exerts obvious effects on stress-strain distribution. The earliest plastic deformation occurs at the edge of the inner surface defect (Type 1), but occurs on the central part of both the outer surface defect (Type 2) and on the double defects (Type 3). The appearance of defects greatly weakens the stability of the pipeline. For equivalent sum total corrosion defect depth, a single defect is more harmful to the pipeline than double defects.
TOPICS: Stress, Corrosion, Pipelines, Pipes, Geometry, Stability, Deformation, Steel, Computer simulation
research-article  
Seikh Mustafa Kamal
J. Pressure Vessel Technol   doi: 10.1115/1.4041339
Autofrettage is a means of generating compressive residual stresses at the inner side of a thick-walled cylinder or hollow disk by causing nonhomogeneous plastic deformation of the material at the inner side. The presence of residual compressive stresses at the inner region of the cylinder/disk enhance the pressure withstanding capacity, fatigue life and the resistance to stress corrosion cracking of the component. Despite the hydraulic and swage autofrettage are the widely practiced processes in industries, there are certain disadvantages associated with these processes. In view of this, in the recent years researchers have proposed new methods of achieving autofrettage. Rotational autofrettage is such a recently proposed autofrettage method for achieving the beneficial compressive residual stresses in the cylinders. In the present work, the rotational autofrettage is studied for a thick-walled hollow circular disk. A theoretical analysis of the residual stresses produced in the disk after unloading are obtained assuming plane stress condition, Tresca yield criterion and its associated flow rule. The analysis takes into account the effect of strain hardening during plastic deformation. Further, the effect of residual stresses in the typical SS304 and aluminum disk is studied by subjecting them into three different types of loads viz., internal pressure, radial temperature difference and rotational speed individually. It is found that the residual stresses due to rotational autofrettage can significantly enhance the internal pressure carrying capacity, radial temperature difference and the rotational speed of the disks with respect to the corresponding disks without autofrettage.
TOPICS: Stress, Disks, Autofrettage, Residual stresses, Pressure, Cylinders, Deformation, Temperature, Aluminum, Flow (Dynamics), Stress corrosion cracking, Compressive stress, Fatigue life, Theoretical analysis, Work hardening
research-article  
Eyas Azzuni and Sukru Guzey
J. Pressure Vessel Technol   doi: 10.1115/1.4041340
The design and fabrication of shop welded and prefabricated relatively small tanks used in the upstream segment of the oil and gas industry is governed by the American Petroleum Institute Specification 12F (API 12F). The tanks designed and fabricated in conformance with API 12F meet the criteria to operate safely with specific internal pressure and vacuum pressure. This study explores the changing the designs of API 12F tanks to include a new rectangular cleanout design with reinforcement as shell extension internally of cleanout frame and a stepped shell design. This study also investigated the introduction of two additional tank sizes in addition to existing eleven tank sizes in the current 12th Edition of API 12F. The adequacy of the new design changes and proposed tank designs were verified by elastic stress analysis with nonlinear geometry, elastic-plastic stress analysis with nonlinear geometry, and elastic buckling analysis to verify their ability to operate at a design internal pressure of 16 oz/in2 (6.9 kPa) and maximum pressure during emergency venting of 24 oz/in2 (10.3 kPa). A vacuum pressure of 1.5 oz/in2 (0.43 kPa) was also investigated using the elastic buckling analysis. The stress levels and uplift of the tanks are reported in this report to provide insights into the behavior of proposed API 12F tanks exposed to higher internal pressure and vacuum pressure.
TOPICS: Design, Failure mechanisms, Shells, American Petroleum Institute, Pressure, Vacuum, Buckling, Geometry, Stress analysis (Engineering), Emergencies, Petroleum industry, Manufacturing, Stress
research-article  
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
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
research-article  
Guohua Liu, Ziyuan Yu, Xu Liang and Changpeng Ye
J. Pressure Vessel Technol   doi: 10.1115/1.4041264
In this paper, modified transfer entropy theory is combined with a surrogate data algorithm to produce a new method in order to identify nonlinearity in the vibration data of a damaged cylindrical shell. The proposed identification method can eliminate the necessity of acquiring baseline statistics by comparing the transfer entropy of original vibration data and it of surrogate data. Moreover, a new index ? is established to reflect the degree of damage by quantifying the discreteness of the entropy of each group of surrogate data. To verify the effectiveness of this method, a semi-analytical method based on a Galerkin method and the classic shell theory is used to precisely predict the linear and nonlinear vibration response of a cylindrical shell under different damage circumstances. The corresponding results show that the proposed method can not only identify large deformation but also be further applied to the identification of structural damage. In addition, the influence of different load pressures and degrees of damage on the effectiveness of the identification method is analyzed and discussed. As verified, the proposed methodology can be potentially used for structural damage identification and evaluation in areas such as civil engineering, mechanical engineering, and ocean engineering.
TOPICS: Entropy, Pipes, Vibration, Damage, Statistics as topic, Galerkin method, Shells, Ocean engineering, Algorithms, Nonlinear vibration, Deformation, Mechanical engineering, Civil engineering, Stress
research-article  
Junya Miura, Terutaka Fujioka and Yasuhiro Shindo
J. Pressure Vessel Technol   doi: 10.1115/1.4041057
This paper proposes simplified methods to evaluate fatigue damage in a component subjected to cyclic thermal loads to visualize damage distribution by using typical CAE systems. The objective is to perform the evaluations on a standard desktop PC within a reasonably short computation time. Three simplified methods for defining elastic stress ranges are proposed in place of the method in the ASME Subsection NH procedures. A thermal fatigue test that was previously performed using a type-304 stainless steel (304SS) cylinder is simulated to validate the proposed methods. Heat transfer and elastic analyses are conducted. Simultaneously with the analyses, fatigue usage factors are calculated using user subroutines formulated in this study, including the three simplified methods and the ASME NH-based method. The calculated values of the fatigue usage factor are visualized using a graphical user interface (GUI) incorporated into a commercial finite-element analysis (FEA) code. The fatigue usage factor distribution obtained using the simplified methods could be calculated without requiring large amounts of memory and long computation time. In addition, the distribution of the fatigue usage factor was consistent with the distribution of cracks observed in the test.
TOPICS: Stress, Fatigue damage, Visualization, Fatigue, Computation, Graphical user interfaces, Finite element analysis, Damage, Cylinders, Heat transfer, Computer-aided engineering, Stress analysis (Engineering), Fracture (Materials), Fatigue testing, Stainless steel, Elastic analysis
research-article  
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
research-article  
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
research-article  
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
research-article  
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
research-article  
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
research-article  
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
research-article  
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

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