Cylindrical Steel Tanks Research Articles

Effects of The Shell Thickness On The Directional Deformation And Buckling On The Cylindrical Steel Water Tanks Under The Kobe Earthquake Loading

Cylindrical steel storage tanks are widely used for the storage of various liquids, industrial chemicals and firefighting waters. They have been used for cooling purposes in nuclear power plants in recent years. Liquid-storage tanks have many different configurations; however, in this study, cylindrical ground-supported liquid steel tanks were preferred because of their simplicity in design and construction as well as their efficiency in resisting hydrostatic and hydrodynamic applied loads, when compared with other configurations. If liquid steel tanks are damaged in an earthquake, they can also cause great financial and environmental damage with their hazardous chemical contents. These tanks may be exposed to some damages such as elephant-foot buckling, diamond-shape buckling, overturning and uplifting during earthquakes. Dimensions of cylindrical open-top, flat-closed and torispherical-closed top tanks were determined for 3D-finite element method (FEM) models in an ANSYS workbench software. This article focuses on the seismic-activity-resistant ground-supported cylindrical (vertical) steel storage liquid tanks. Seismic analyses were conducted under Kobe earthquake loads. The frequency values calculated with API 650 were verified with the FEM model results. Directional deformation, buckling results were presented for both impulsive and convective regions. According to API 650 standard, the tank shell thickness is 6 mm. Simulations were performed with 4 mm and 8 mm shell thickness for tanks. In this study, directional deformation and buckling were observed with simulations made by choosing the shell thickness under (4 mm) the standard and above (8 mm) the standard, unlike the approaches in the literature. As a result, it was observed that the 8 mm shell thickness determined above the standard increased the deformation in the flat-closed tank. In addition, torispherical dome-shaped tanks have been observed to lower directional deformation and buckling in any case. The differences obtained are detailed with

Cost-effectiveness analysis of tank and base foundation diagnostics without paintwork removal

The article describes the particular qualities of application of a cylindrical steel tanks' and base foundation technical inspection method without removal of a protective covering. The model is formed and the basic parameters of an estimation of economic efficiency of carrying out of diagnostics are determined. The economic efficiency of application of the modern method of vertical steel tank examination is estimated. The high economic efficiency of the new technological method is substantiated in comparison with the traditional method. It is established that the advantage of using the innovative diagnostic method in comparison with the traditional method is fully manifested when it is necessary to maintain a large fleet of tanks. It is calculated that, given the design parameters, the savings in the use of the method proposed by the authors in the long term are 1773.2 million rubles compared with traditional. The use of a new technological method - the technology of diagnosing vertical steel tanks without removing the protective coating, allows to reduce the total cost of conducting diagnostics with a discount of 8.7 times. Dependences were obtained of the discounted volume of expenses on acquisition of the equipment and the subsequent diagnostics of vertical steel tanks on the operation time of the vertical steel tanks.

Seismic assessment of an industrial frame-tank system: development of fragility functions

Evidence from past earthquakes has shown high levels of damage to industrial facilities, demonstrating that seismic loading can cause damage or failure, not only to the main structural elements, but also to secondary or non-structural components. In contrast to other types of building structures, failure of a secondary component could imply both huge downtime costs for low intensity/high probability events and catastrophic accidents for high intensity/low probability events. It is thus necessary to investigate the seismic vulnerability of industrial plants in a comprehensive manner, that is (1) by including both structural and non-structural components in the framework of analysis; and (2) by giving full account of multiple damage conditions, which entails identification/consideration of a wide range of seismic intensities. In light of this, the analyses presented in this paper fall within a probabilistic framework and focus on the derivation of seismic fragility functions at multiple damage states, which describe the physical vulnerability of an industrial frame supporting a cylindrical steel tank. The structure in question is a steel special concentrically braced frame, whilst the tank is a small liquid-storage item commonly used for a vast variety of industrial processes. To begin with, a fibre-based finite element model of the supporting structure was developed within an open-source platform, and then an incremental dynamic analysis was carried out by considering 47 natural accelerograms that were scaled to 9 seismic intensities. For the first run, the mass of the tank was lumped together with that of the rest of the structure, and acceleration floor spectra were computed, permitting the evaluation of the maximum response of the tank, as completely uncoupled from the structure. Additionally, a second analysis was run to explicitly account for both the dynamic interaction between the frame and the tank as well as the hydrodynamic response of the fluid-tank system. To this end, use was made of a well-known analytical model that treats the impulsive and convective components of motion as two uncoupled single degree of freedom systems. Demand resulting from both methods of analysis was convolved with capacity corresponding to the attainment of limit state conditions for both the frame and the tank. Fragility models were derived and compared so as to evaluate the vulnerability of the case study as well as the effectiveness of both analysis approaches.

Strengthening of Cylindrical Steel Water Tank Under the Seismic Loading

Cylindrical steel tanks are widely used to water store and for cooling in nuclear power plants. The seismic behaviour of liquid storage tanks is very complicated due to the hydrodynamic pressures of the fluids in them. In this paper, the epoxy-carbon coating method is suggested to improve of seismic performance of cylindrical steel tanks. Composite epoxy-carbon materials are widely used for winding thin walled cylindrical steel structures. After tank had coated with epoxy–carbon composite material, it was observed that Equivalent (von-Mises) stresses significantly decreased. The maximum hoop stress in the unprotected tank is 81.92 MPa, while the maximum stress is reduced to 44.77 MPa after it was coated with the epoxy-carbon.

Observational Seismic Fragility Curves for Steel Cylindrical Tanks

The evaluation of seismic vulnerability of atmospheric above ground 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 above ground 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 have 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 are included in fragility analysis. The hazard parameter used is the peak ground acceleration (PGA). Seismic fragility curves obtained from the described procedure are compared to those available in the technical literature.

Recent results and future prospects of Super-Kamiokande

Abstract Super-Kamiokande (SK) is a water Cherenkov detector located 1000 m underground in Kamioka Observatory , ICRR, University of Tokyo in Japan. It consists of a cylindrical stainless steel tank, 50,000 ton of purified water, and 11,000 of 20-inch PMTs. The fiducial volume of the SK detector is 22.5 kton. The experiment was started in April 1996, and currently phase IV (SK-IV) is running. SK has been the world largest water Cherenkov detector with purified water in underground since 1996. SK has a variety of measurement or physics targets, namely, solar neutrinos , atmospheric neutrinos , supernova neutrinos, neutrinos produced by the accelerator in J-PARC (as T2K experiment), and search for nucleon decay. In near future, we are going to move to the next phase, that is SK-Gd. In the SK-Gd phase, we are planning to add 0.1% of gadolinium to the current SK detector in order to enhance neutron tagging efficiency, and then try to achieve the first observation of supernova relic neutrinos (SRN) (or diffuse supernova neutrino background (DSNB)). The initial work in this upgrade project was started in June 2018. This paper reports a brief summary of the SK experiment, recent solar neutrino results, and recent atmospheric neutrino results. As a future plan, the purpose of SK-Gd and status of the upgrade work are reported.

Improving proposals for design standards of vertical cylindrical steel tanks for oil and oil products storage

The calculation of subsidence points along the contour and in the center of the tank bottom is complicated in the case of erosion on inhomogeneous, subsidence, damaged soils, mules, flooded and seismically dangerous areas. The article analyzes the most dangerous geological phenomena, processes and complicated geotechnical conditions for the territory of Ukraine. The method of an artificial base arrangement with improved properties due to vertical reinforcement by soil cement elements is considered. Techno-economic comparison of the proposed variant with the usual pile variant of foundations (subsidence soils, estimated seismic intensity of 9 points) has been carried out. Probabilistic analysis of the artificial base has been carried out and the corellation between the probability of its failure from the percentage of reinforcement has been determined.

The Experimental Design of Stone Columns' Modelling using Small-Scale Unit Cells: A Review

This paper presents a review of the experimental design of the small-scale single stone column that adopts the unit cell concept. Materials and methods used in experiments along with their effects and implication have been appraised. The reviewed cases showed that clayey soils were often used to construct the host ground. Steel cylindrical tanks were used with diameters ranging from 15 to 60 cm and heights ranging from 20 to 120 cm. For such scale, the used stone size is 2 to 10 mm. Plates load test can be carried out on the entire tank or on the stone column. The load has been imposed at a constant settlement rate of 1 to 1.25 mm/min in order to simulate the stage immediately after construction. The review shows that remoulding and replacement have been often practised for the construction of the host ground and the stone column, respectively.

Seismic damage criteria for a steel liquid storage tank shell and its interaction with demanded construction material

In this paper, the relation between the steel cylindrical tank geometry and the governing critical damage mode of the tank shell is numerically determined for all practical ranges of liquid storage tanks (aspect ratio H/D = 0.2 to 2). In addition, the interaction between the seismic intensity, soil type, acceptable seismic risk and tank geometry along with the extra material demanded by the seismic loads is examined based on the provisions of major codes. The importance of seismic factors on the economics of the design of a liquid tank in zones with high seismic activity is comprehensively discussed. In this regard, an empirical relation to estimate the steel volume required for specific seismic conditions and tank geometries is proposed based on the results of analysis.

Shaking Table Test of Steel Cylindrical Liquid Storage Tank Considering the Roof Characteristics

Steel cylindrical tanks are widely used for the storage of hazardous substances of which leakage must be prevented under any circumstances. However, the dynamic response of the steel cylindrical liquid storage tank depends sensitively on the fluid–structure interaction and the vibration of the tank structure and necessitates clarification for the safety of the tank structure. This paper presents the results of shaking table tests performed to examine the dynamic behavior of a scaled cylindrical steel tank model considering the presence or not of fixed roof and added mass at the top of the tank for various fluid levels. The test results confirm the occurrence of both beam-type and oval-type vibration modes and show that the larger content of liquid inside the container amplified the acceleration along the height of the cylindrical tank. The oval-type vibration modes are seen to be more dominant in case of large water-to-structure mass ratio.

Experimental study on the seismic response of liquid storage tanks with Sliding Concave Bearings

It is known that, earthquakes have caused severe damages to a large number of industrial facilities, mainly storage tanks with extremely serious economic and environmental implications. Thus, it is extremely importance to use techniques for reducing the seismic vulnerability of such structures. Seismic base isolation as seismic protection technology is already known and its development continues to grow. The present paper focuses on the seismic performance of broad and slender atmospheric storage steel tanks base isolated by Sliding Concave Bearings (SCB). The performance study carried out through shaking table tests on a vertical cylindrical steel tank model allowed to determine quantitatively the efficiency of the SCB by analyzing two structural parameters: (a) sloshing height and (b) base shear force. Six real ground motions with different characteristics were considered. Results show the effectiveness of SCB in reducing the base shear force values for all studied cases without significantly affecting the sloshing displacements when compared with fixed-base support.

Buckling behavior of cylindrical steel tanks with concavity of vertical weld line imperfection

Shell structures are built using a number of welded curved panel parts. Hence, some geometrical imperfections emerge. These imperfections have a direct impact on structural behavior of shells during the external compressive loading. In this research, a field study was accomplished on the implementation of the storage tanks in a refinery site and then, the resulted imperfections were identified and categorized. The survey of imperfections revealed that the imperfection in form of concavity of vertical weld line is the most prevalent type of imperfection seen in the steel tanks. This imperfection experimentally modeled and the buckling behavior of these tanks was evaluated under uniform external pressure. Comparing obtained results of estimation, ASME code and experimental research represented a considerable difference in the amount of buckling load. Results show that the imperfections due to concavity of vertical weld line are very important in buckling of the tanks under uniform external pressure. This imperfection decreases initial, full and post buckling capacity of the tanks under uniform external pressure, significantly. Findings of this research show that for design of steel tanks under uniform external pressure load, 65% of the buckling load obtained from the ASME Code should be used.

Effect of local geometrical imperfection on dynamic buckling of cylindrical storage tanks

Steel cylindrical tanks are the most susceptible to damage due to dynamic buckling during earthquakes. The production of cylindrical shell without imperfections is very difficult or sometime even impossible. The most previous research to study the geometrical imperfection in the shell of steel tanks using various methods did not deal with the fluid–structure interaction (FSI) and the dynamic loads. In this paper, the FSI numerical model is used to estimate the effect of local geometrical imperfection with dynamic buckling of fluid-filled tanks. The liquid inside the tank was modeled using specific Ansys’s finite elements and fluid–structure interaction. The calculation includes modal and time history analysis, including material and geometric nonlinearity. Then a typical cylindrical tank is analyzed by the application of three different stability criteria to estimate the critical PGA. The obtained dynamic buckling results of the perfect and imperfect tank are compared. The effect of geometrical imperfection on dynamic buckling is clearly shown. The PGAcr of the imperfect tank models decreases by 09.11%.

Thermal buckling behaviour of unstiffened and stiffened fixed-roof tanks under non-uniform heating

The problem addressed in this paper is the thermal buckling behaviour of thin-walled steel cylindrical fixed-roof tanks under non-uniform loading, induced by an adjacent tank. This specific type of thermal loading can be triggered by a neighboring tank fire where heat is transferred mainly through radiation. Since the calculation of the temperature field of the heated tank lies in other scientific fields (e.g. Computational Fluid Dynamics), a thermal pattern, proposed in literature, is used for the simulation of the fire-induced load and the investigation of the structural response of the tank due to heating. The study is conducted numerically through the Finite Element method, using coupled thermo-mechanical analysis. The general purpose Finite Element code MSC Marc, is used for the simulation. Three-dimensional models are developed using shell elements. Firstly, a detailed study of the failure mechanisms that take place in case of non-uniform loading is carried out. Furthermore, tanks with different geometries are studied. The main objective is the calculation of the critical temperature i.e. the temperature where the failure appears and the determination of the failure modes. Finally, a parametric study is conducted for the evaluation of the effectiveness of stiffening methods that are commonly used at ambient temperature design (stiffeners and stepwise wall thickness), in the case of the non-uniform heating load. In this study, the heated tanks are considered to be empty, which is the most severe scenario, for their structural integrity.

Анализ закономерностей развития осадок фундаментов стальных цилиндрических резервуаров на слабых грунтах

Анализ закономерностей развития осадок фундаментов стальных цилиндрических резервуаров на слабых грунтах

Numerical analysis of the cylindrical rigidity of the vertical steel tank shell

The paper deals with the study of rigidity of a vertical steel cylindrical tank and its structural elements with the development of inhomogeneous subsidence in ANSYS software complex. The limiting case is considered in this paper: a complete absence of a base sector that varies along an arc of a circle. The subsidence zone is modeled by the parameter n. A finite-element model of vertical 20000 m3 steel tank has been created, taking into account all structural elements of tank metal structures, including the support ring, beam frame and roof sheets. Various combinations of vertical steel tank loading are analyzed. For operational loads, the most unfavorable combination is considered. Calculations were performed for the filled and emptied tank. Values of the maximum possible deformations of the outer contour of the bottom are obtained with the development of inhomogeneous base subsidence for the given tank size. The obtained parameters of intrinsic rigidity (deformability) of vertical steel tank can be used in the development of new regulatory and technical documentation for tanks.

Field Study and Evaluation of Buckling Behavior of Cylindrical Steel Tanks with Geometric Imperfections under Uniform External Pressure

Construction and assembling process of shell structures has caused main problems. In these structures, there is no possibility for the integrated construction due to their large shell extent and they are built using a number of welded curved panel parts; hence, some geometrical imperfections emerge. Most of these imperfections are caused by the process of welding, transportation, inappropriate rolling, as well as installation and implementation problems. In this research, construction of steel cylindrical tanks in one of the refinery site is monitored using a field survey and created imperfections are identified and introduced. Relying on the statistical inference, they are classified and then, by studying the effective factors and origin in their generation, the common imperfections are identified. The impact of common imperfections on the buckling behavior is experimentally evaluated under uniform external pressure. Then, nonlinear analysis of the test specimens are performed by ANSYS software. Finally experimental results, finite element and analytical relations are compared. The obtained results show that the imperfections have a direct impact on the structural behavior of shells during the buckling under uniform external pressure load. Also, some imperfections caused by welding increase the buckling resistance of cylindrical shells.

Design procedure for liquid storage steel conical tanks under seismic loading

Steel conical liquid tanks are widely used for the purpose of liquid storage. Despite the fact that some of these tanks have failed lately, most of the seismic design guidelines focus on the design of steel cylindrical tanks with the only design guidelines for conical tanks based on using an equivalent cylinder approach, which is not based on any theoretical or experimental basis. In this study, a simplified procedure is proposed to design steel conical tanks subjected to horizontal and vertical excitations. The proposed procedure is based on satisfying a design formula that combines the ratio of seismic demand to the tank resistance due to horizontal and vertical excitations including geometric imperfections. The design procedure is then validated by comparing its outcomes with those obtained using time history analysis. The study is carried out numerically using an in-house nonlinear finite element model.

Buckling strength of cylindrical steel tanks under measured differential settlement: Harmonic components needed for consideration and its effect

In practical engineering, the measured differential settlement can be gained by monitoring the points beneath the tank wall and it can induce the buckling of the tank even with a small amplitude. In general, Fourier series is adopted to decompose the measured differential settlement into harmonic components with various wave numbers. However, the question that which harmonic components should be considered is a main challenge for buckling investigations of the tank under measured differential settlement. In this work, a recommendation for harmonic components needed for consideration was proposed when decomposing measured differential settlement into harmonic components in terms of Fourier series. Moreover, the effects of the harmonic components considered on buckling behavior of floating roof tanks and conical roof tanks were discussed. The results presented that three monitoring points can make a first estimate of ovalling and the harmonic components considered should be smaller than and equal to [N]/3 ([] is the rounding function and N is the number of the monitoring points). The introduction of the harmonic component with a high wave number can cause the change of the buckling modes of the tanks under differential settlement, including floating roof tanks and conical roof tanks. Meanwhile, it can decrease the buckling strength of the floating roof tank more significantly than that of the conical roof tank.

Experimental and numerical study of the response of cylindrical steel tanks under seismic excitation

To improve the structural seismic response of liquid storage tanks, in the last 50 years, many researchers have developed different mathematical models, ranging from those based on discrete elements such as simplified two-mass models to those involving fluid–structure interactions by complex formulations. To provide a broad overview on the scope and accuracy of different numerical linear models, in this paper, a comparative study based on the dynamic response assessment of cylindrical ground-supported containers under seismic excitation is conducted. The dynamic response in terms of liquid sloshing height, base shear force and overturning moment is analysed by means of: (a) a simplified mechanical model in which the behaviour of the liquid is represented by a discrete mass-spring system; (b) a complex model based on a Lagrangian fluid finite element approximation and (c) an experimental scaled model whose measured response is considered as benchmark. To obtain robust estimators of the structural response, three different types of cylindrical tanks, including broad and slender tanks, subjected to real ground acceleration time-histories are studied. The results indicate that the finite element model gives good approximation for all response parameters and the simplified mechanical model underestimate the sloshing height and overestimate base shear force and overturning moment.