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Liquid storage tanks are often arranged in rows with small spacing in practical applications, which may cause mutual influence under earthquake action and even aggravate the seismic damage of liquid storage tanks. Adding the vibration barrier (ViBa) into the foundation between the adjacent liquid storage tanks forms a new type of seismic control method. Considering important factors such as liquid–solid–soil coupling, liquid sloshing behavior, and structure–soil–structure interaction (SSSI), a refined 3D numerical calculation model of the adjacent liquid storage tanks with three ViBas is established by ADINA. The influence of seismic wave incidence angle on the seismic responses of the liquid storage tanks and the control effect of ViBa are studied, and the parameter influence analysis is carried out. The results show that the ViBa significantly control the seismic responses and liquid sloshing wave height of the adjacent liquid storage tanks, and the damping ratio of the liquid sloshing wave height is between 30% and 40%. When the seismic incidence angle is between 30 ∘ and 60 ∘ , the dynamic responses of the liquid storage tank is larger. With the increase of the seismic incidence angle, the control effect of the ViBa on the effective stress, hoop stress, axial compressive stress, and liquid pressure first increases and then decreases. When the liquid storage tank is close to full state, the control effect is most significant at an incidence angle of 60 ∘ , and the control effect of the ViBa on the liquid storage tank with medium height-diameter ratio is the best. [ABSTRACT FROM AUTHOR]

A new damping control method for the adjacent liquid storage tanks (LSTs) based on vibration barrier (ViBa) is proposed. Considering liquid-solid-soil coupling and structure-soil-structure interaction, a three-dimensional numerical calculation model is established by ADINA. The seismic control effect of ViBa is investigated, and parametric analysis is carried out. The results show that ViBa has a significant control effect on seismic responses and wave height, and the reduction factor of base shear force reaches the maximum value of 49.26%. The larger the seismic intensity, the liquid storage height and the height-radius ratio, the larger the reduction factor of the ViBa. [ABSTRACT FROM AUTHOR]

Storage tanks are extensively used containers in various industries for storing diverse liquids. The sloshing of liquid in these containers, often caused by earthquakes, is an emerging issue in the context of damage sustained by tanks. Thus, the seismic resilience of a tank is a critical performance criterion in tank design. Given the complexity of liquid sloshing, the fundamental characteristics of this phenomenon must be examined to gain insights into fundamental sloshing behavior. Liquid sloshing typically involves a combination of fundamental and higher sloshing modes, and the modes and frequencies of liquid sloshing are therefore crucial for assessing this complex behavior. In this study, a shaking table test was employed to analyze the characteristics of liquid sloshing modes. The shapes of the first three sloshing modes under unidirectional excitation were determined and used to validate their symmetry. The findings indicate that the first sloshing mode exerts a more pronounced influence on liquid sloshing during free oscillation induced by unidirectional and horizontal excitation. The modal contribution factor of the first sloshing mode escalates with an increase in the ratio of the liquid level to the length of the tank parallel to the shaking direction, eventually converging toward a constant value. [ABSTRACT FROM AUTHOR]

The probability of seismic pounding of sliding isolation liquid storage tank (LST) is high. Considering normal impact force and tangential friction force at the location of pounding under bidirectional earthquake, a 3D calculation model of sliding isolation LST is established based on a finite element method. Pounding dynamic responses under unidirectional and bidirectional earthquakes are comparatively investigated, and frequency domain analysis is also conducted. Finally, mitigation measure for adverse effect caused by the pounding is proposed. Results show that the influence of concrete nonlinearity on the pounding is very significant. Dynamic responses are significantly increased due to the pounding, and the maximum tensile stress of tank wall reaches 2.510 MPa under ChiChi earthquake, which exceeds the concrete tensile strength. Besides, pounding causes a high-frequency response. A reasonable rubber cushion design can ensure that the maximum displacement of the sliding isolation LST is limited by the moat wall, and the failure probability caused by the pounding is decreased.

Liquid storage tank is widely used in the petrochemical industry, earthquake will lead to structural damage and secondary disasters, and damping control opens up a new way for seismic design of liquid storage tank. Considering soil-structure-fluid interaction, liquid sloshing dynamic behavior and material nonlinearity, a three-dimensional calculation model of shock absorption liquid storage tank is established by combining sliding isolation and displacement-limiting devices. The dynamic responses of the liquid storage tanks under the action of Kobe and El-Centro waves are investigated, and the influence of soil-structure interaction (SSI) on the dynamic response is discussed. The results show that the damping ratio is basically between 30% and 90%. After the SSI is considered, the damping ratio of liquid sloshing wave height is increased, while the damping ratio of the dynamic response of the liquid storage tank is decreased, and the change of elastic modulus has little effect on the damping effect. The sliding isolation with displacement-limiting devices has significant damping control effects on the liquid sloshing wave height and the dynamic responses of the liquid storage tank.

Liquid storage tanks are widely used in the industrial and the agricultural production, the earthquake damage of the liquid storage tanks will not only lead to economic losses, but also may cause environmental pollution, fire and explosion. Considering the fluid–structure interaction, the liquid sloshing and the material nonlinearity, the three-dimensional numerical calculation models of nondamping and tuned mass damper (TMD) liquid storage tanks are established, respectively. The earthquake waves with different characteristics are selected to investigate the dynamic responses of the liquid storage tank, the control effects of the TMD on the seismic responses of the liquid storage tank are analyzed, and the influence law of the change of the spring stiffness on the damping effect is discussed. The results show that the TMD has a significant damping effect on the liquid storage tank, and the element damping has significant influence on the dynamic responses in the subsequent stage of the earthquake action. Under the action of Darfield–New Zealand wave, the damping ratio corresponding to the acceleration of the tank wall is 69.6%. When the element damping is not considered, the small change of the spring stiffness has significant influence on the damping effect, but after the element damping being considered, the influence of the spring stiffness change on the damping effect is small. The TMD provides a high performance system to the damping control of the liquid storage tank under the action of earthquakes with different intensity. [ABSTRACT FROM AUTHOR]

Effects of soil-structure interaction (SSI) on the seismic performance of cylindrical ground-supported liquid storage tanks are studied. The present study attempts to investigate the effects of uncertainties, associated with the critical soil parameters, on the seismic behavior of liquid storage tanks. Random multi-layered soil models coupled with the fixed base liquid storage tank are developed and analyzed. Further, the tank structure is considered base-isolated with lead rubber bearing and analyzed with the same set of soil models, to investigate the seismic behavior of base-isolated tank under uncertain soil condition. A set of three ground motions are selected from a large suite through a mean spectral matching scheme for investigating the effect of soil uncertainties on the seismic response. Distributions of the peak seismic response quantities observed herein show that the uncertainties in soil parameters critically affect the seismic responses of fixed base and base-isolated liquid storage tanks. Sloshing displacement of fixed base and base-isolated tanks is affected by both uncertainty in the soil parameters and ground motion characteristics. Nevertheless, for ground-supported tank, relatively larger dispersion or variability of base shear and overturning moment, as compared to that of the sloshing response, is observed. [ABSTRACT FROM AUTHOR]

Globally, tanks play a major part in the provision of access to clean drinking water to the human population. Beyond aiding in the supply of fresh water, tanks are also essential for ensuring good sanitary conditions for people and for livestock. Many countries have realized that a robust water supply and a robust sanitation infrastructure are necessary for sustainable growth. Therefore, there is large demand for the construction of storage tanks. Further, liquid storage tanks are crucial structures which must continue to be operational even after a catastrophic natural event, such as an earthquake, to support rehabilitation efforts. From an engineering point of view, the various forces acting on the tanks and the behaviour of the tanks under various loads are important issues which need to be addressed for a safe design. Analyses of the tanks are challenging due to the interaction between the fluid and tank wall. Thus, researchers have conducted several investigations to understand the performance of storage tanks subjected to earthquakes by considering this interaction. This paper discusses the historical development of various modelling techniques of storage tanks. The interaction with the soil also influences the behaviour of the tanks, and hence, in this paper, various modelling approaches for soil structure interaction are also reviewed. Further, a brief history of various systems of base isolation and modelling approaches of base-isolated structures are also discussed in this article. [ABSTRACT FROM AUTHOR]

As one of the three important characteristics of ground motion, the impact of ground motion duration on the dynamic responses of structures necessitates further in-depth research. Seven different definitions of ground motion duration are selected. The three-dimensional numerical calculation models of non-damping liquid storage tank (LST), rubber-isolated LST, isolated LST based on positive and negative stiffness in parallel, and isolated LST based on positive and negative stiffness in series-parallel are established by ADINA, and the dynamic responses of the different LSTs under earthquakes with different definitions of ground motion duration are comparatively studied. The results show that the influence of different definitions of ground motion duration on the dynamic responses of LST can not be neglected. The dynamic responses are larger under the long-duration ground motion compared to the short-duration ground motions, besides, and the three types of isolation exhibit better performance under long-duration ground motions than under short-duration ground motions. The damping effect of the positive and negative stiffness in series-parallel is the best. The rubber isolation has an amplifying effect on the liquid sloshing wave height, while the isolated system with negative stiffness can make up for this deficiency. Reasonable arrangement of negative stiffness device in isolation layer of LST is helpful to realize dual control of structure responses and liquid sloshing wave height. (1) A new method for improving seismic performance of isolated liquid storage tank based on positive and negative stiffness is proposed. (2) Dynamic responses of different liquid storage tanks under earthquakes with different definitions of ground motion duration are comparatively studied. (3) The damping effect of the positive and negative stiffness in series-parallel is the best. (4) Introducing negative stiffness into the isolation layer of liquid storage tank can reduce liquid sloshing wave height. [ABSTRACT FROM AUTHOR]

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This is a study on a deep, liquid‐containing tank, such as an overhead water tank on a building, with a vertically submerged stretched membrane (SSM). Here, instead of the sloshing mode, which can become detuned and also affords a low damper mass ratio, the impulsive liquid–membrane interacting system is designed to serve as a dynamic vibration absorber. The requirement of tuning the frequency of the impulsive liquid–membrane interacting system to the structural frequency can be achieved without any imposition on the tank dimensions, which are generally fixed from the tank's functional requirements. The system frequency would remain unchanged so long the membrane would remain submerged below a minimum liquid depth, thereby allowing fluctuation of liquid level within a prescribed range of the tank depth. The formulation for obtaining the frequency of the impulsive liquid–membrane interacting system is derived, using the sub‐domain partition approach. It is seen that through suitable adjustment of the design parameters of the membrane, the proposed tank damper can be tuned to both short‐period and to long‐period structures. Further, the impulsive liquid mass, which otherwise has no role to play in the damping mechanism of a tuned liquid damper (TLD), is here utilized to absorb and dissipate the vibrational energy. Through a time‐domain study considering recorded seismic accelerograms, the significant control effectiveness of the proposed damper system is illustrated. Further, the results obtained from the equivalent mechanical model of the structure–damper system are compared with those from a finite element analysis of the fluid–structure system in the ANSYS Workbench environment. [ABSTRACT FROM AUTHOR]

A detailed numerical framework for seismic analysis of liquid storage tanks considering soil-structure interaction (SSI) is presented. Lumped mass model for the tank and finite element approach for the soil domain are adopted. Effects of SSI on seismic performance of ground supported and elevated liquid storage tanks, with fixed base and base isolated conditions, are studied under near-field and far-field ground motions. Effect of SSI on fixed base tanks is found to be similar under different types of ground motions. Nevertheless, effectiveness of isolation systems with different stiffness characteristics depends on soil type, tank slenderness ratio, and ground motion types. [ABSTRACT FROM AUTHOR]

Base shear and sloshing response control in ground-supported circular cylindrical liquid storage tank is achieved by oblate spheroid base isolation (OSBI) system used along with floating surface diaphragm on the contained liquid. The new base isolation system, OSBI proposed herein is based on rolling-friction mechanism in ellipsoidal-shaped isolators in both the horizontal axes. The surface diaphragm is proposed to float on the free liquid surface to control the sloshing amplitude. The tank is analyzed using the coupled acoustic-structural (CAS) approach in finite element method (FEM). In order to have conformity of the present FE model, the FEM results are compared with the mechanical lumped-mass model of the tank (without surface diaphragm). The seismic response is investigated for the tank subjected to harmonic and real-earthquake excitations. The parameters considered for the analysis are the aspect ratio of the tank, eccentricity of the isolator, and thickness of the diaphragm. The seismic response quantities evaluated are base shear, sloshing displacement, and impulsive hydrodynamic pressure in the tank. Further, to study the effectiveness of the OSBI, the seismic responses of the tank subjected tri-directional components are compared with the two horizontal bi-directional components of the earthquakes. Also, the sloshing displacement with and without surface diaphragm in the non-isolated and base-isolated tanks are compared. From the results, it is observed that the OSBI system is efficient in mitigating the seismic responses in the tanks and the surface diaphragm is efficient in controlling the sloshing displacement. The superior performance of the proposed isolator depends on the design parameters, namely, eccentricity, and coefficient of rolling friction selected. The effectiveness of the surface diaphragm depends on the choice of material and thickness adopted. [ABSTRACT FROM AUTHOR]

In order to study the seismic response of liquid storage tank under bidirectional seismic excitation, the 15×104 m3 vertical unanchored liquid storage tank was taken as the object, and numerical analysis on seismic response of vertical unanchored tank was conducted with the finite element software ADINA, considering the contact nonlinear. The whole system was mainly divided into two parts, i.e., the basic isolation components and the liquid-structure interaction subsystem. The structure and liquid region of the tank were simulated with the shell element and potential fluid element respectively, and the three-dimensional isolation was equivalently replaced by a spring-damping system. Subsequently, analysis of uplift response, acceleration time history, liquid sloshing height, wall stress change, base shear and overturning moment was carried out for the liquid storage tank with Bathe integration method. The results show that: under the excitation of El-Centro seismic wave, the tank bottom is uplifted before seismic isolation and the uplift area is in the shape of "crescent", which disappears after seismic isolation. Installing a seismic isolation layer in the liquid storage tank could effectively reduce the dynamic response such as acceleration, wall stress, base shear force and overturning moment. However, liquid sloshing height of the liquid storage tank after seismic isolation increases. The research results could provide reference for the seismic isolation design of liquid storage tank.

Variable curvature friction pendulum bearings (VCFPB) effectively reduce the dynamic response of storage tanks induced by earthquakes. Shaking table testing is used to assess the seismic performance of VCFPB isolated storage tanks. However, the vertical pressure and friction coefficient of the scaled VCFPB in the shaking table tests cannot match the equivalent values of these parameters in the prototype. To avoid this drawback, a real-time hybrid simulation (RTHS) test was developed. Using RTHS testing, a 1/8 scaled tank isolated by VCFPB was tested. The experimental results showed that the displacement dynamic magnification factor of VCFPB, peak reduction factors of the acceleration, shear force, and overturning moment at bottom of the tank, were negative exponential functions of the ratio of peak ground acceleration (PGA) and friction coefficient. The peak reduction factors of displacement, acceleration, force and overturning moment, which were obtained from the experimental results, are compared with those calculated by the Housner model. It can be concluded that the Housner model is applicable in estimation of the acceleration, shear force, and overturning moment of liquid storage tank, but not for the sliding displacement of VCFPBs. [ABSTRACT FROM AUTHOR]

Damage of liquid storage tanks (LSTs) due to earthquakes has increased the base isolation systems' demand. As base isolation is a proven control system for mitigating the damages in typical load-bearing structures, its implementation in LSTs is undoubtedly of interest. In the current study, the seismic performance of the base-isolated 3D model of concrete LSTs is investigated under two-component earthquakes as not much literature is available on the subject. The ABAQUS software is used for nonlinear analyses of the base-isolated LST in which liquid and isolators are modeled by the arbitrary Lagrangian–Eulerian and connector elements. For the numerical study, two concrete LSTs of the square and rectangular plans are considered with five lead rubber bearing isolators. The change in response quantities of interest is evaluated under parametric variations, including the type of earthquake, peak ground acceleration, the angle of incidence of the earthquake, and the effective period of the isolator. The response quantities of interest considered are shear forces, overturning moments, top board displacements, hydrodynamic pressure, sloshing height, and Von-Mises stress. The results of the numerical investigation show that the efficacy of base-isolated 3D LST should be assessed at least under a two-component earthquake. Further, the study shows that base isolation is highly effective in controlling seismic stresses developed in LST under two-component earthquakes. [ABSTRACT FROM AUTHOR]

Cylindrical liquid storage tanks are vital lifeline structures, playing a critical role in industry and human life. Damages to these structures during previous earthquakes indicate their vulnerability against seismic events. A novel strategy to reduce the seismic demands in the structures is the use of metamaterials, being periodically placed in the foundation, called MetaFoundation (MF). The periodic configuration of metamaterials can create a stop band, leading to a decrease in wave propagation in the foundation. The aim of this paper is to study the effect of MF on the dynamic behaviour of liquid storage tanks. To that end, the governing equations of motion of the liquid storage tank equipped with MF are derived and solved in the time domain to obtain the time history of the responses under a set of ground motions. Then, the peak responses of tanks, mounted on MF, are compared with the corresponding responses in the fixed base condition. Besides, a parametric study is performed to assess the effect of the predominant frequency of earthquakes, the number of layers of metamaterials, the thickness of soft material, and the damping ratios of soft material on the performance of the MF. The obtained results indicate that the MF improves the dynamic behaviour of the squat tank, in which the mean ratio of responses using MF to the ones in the fixed base conditions equals 0.551 for impulsive displacement, overturning moment, and base shear. [ABSTRACT FROM AUTHOR]

This paper is aimed at investigating the feasibility of using shape memory alloy (SMA) materials as anchor bolts in steel liquid storage tanks. The seismic performance of a case study liquid storage tank anchored with steel and SMA bolts is evaluated. For this purpose, a parametric study is performed to determine the optimum length and diameter of the anchor bolts which results in the minimum tank uplift. Furthermore, incremental dynamic analyses (IDAs) are performed to gain insights into the effects of the axial stiffness of the anchor bolts on the uplift of the tank. The uncertainties regarding the seismic input, i.e., the record-to-record variability and seismic intensity, are taken into account by selecting a set of near-field earthquake ground motion records with and without forward directivity. It should be noted that peak ground acceleration (PGA) is chosen as the intensity measure in IDAs. According to the results, using steel anchor bolts significantly reduces the uplift of the tank due to their high axial stiffness, which may result in a severe damage at the connection as a result of high axial forces in the bolts. Conversely, the self-centering feature of SMA anchor bolts allow the tank to undergo a limited uplift, which also leads to significant energy absorption. Furthermore, the Incremental dynamic analysis results show that tanks anchored with SMA bolts are less sensitive to the frequency content of the seismic input compared to the tanks anchored with steel bolts. Based on the findings of this research, it is possible to reduce the required diameter of the anchor bolts and eliminate the residual deformation of the anchorage system after a severe seismic event by using SMA anchor bolts.

Despite the proven effectiveness of tuned liquid dampers (TLDs), readily available liquid storage tanks are rarely utilized for vibration control of laterally-excited structures, as these are deep tanks with low inherent damping. Further, the fluctuation in liquid level in these tanks also causes variation in the fundamental sloshing frequency, leading to detuning. To overcome these problems, a novel TLD with floating base (TLD-FB) is proposed, in which a constant and shallow liquid level is maintained between the free liquid surface and the floating base. The liquid above the floating base acts as a conventional shallow TLD that always remains tuned to the structural frequency. The paper demonstrates how the TLD-FB can be incorporated into a water storage tank system on an example building without disturbing its functionality and achieves structural response reduction, despite water level fluctuations in the tanks. [ABSTRACT FROM AUTHOR]

Ground-supported cylindrical tanks are used to store a variety of liquids, e.g. water for drinking and fire-fighting, crude oil and liquefied natural gas. Tanks are critical components of modern industrial facilities and life-line systems, and must be designed to withstand safely the earthquakes to which they are subjected. The failure of such systems may lead to environmental hazard, loss of valuable contents, and disruption of fire-lighting elements following destructive earthquakes. Water storage tanks, in particular, are important to the continued operation of water distribution systems in the event of earthquakes. Recent earthquakes have shown liquid storage tanks to be vulnerable to damage. Elasto-plastic shell buckling called "Elephant's Foot" Buckling (EFB) has been the critical aspect in the earthquake resistant design or retrofit of steel cylindrical tanks. In this paper, an innovative method based on using seismic energy absorbing connection at the base of tank wall is introduced to protect the liquid storage tank against seismic loads. In this method, the tank wall is fully disconnected from the base plate and the special connection is provided at the bottom of the tank. The connection is supported by a ring of rigid foundation and the base plate is supported directly on the ground. The seismic performance of the method is numerically examined for one broad and one slender steel tank. It is shown that this method can prevent the EFB of the tank wall by using the plastic deformation of the connection. Numerical results confirm the efficient performance of the proposed system to reducing seismic vulnerability of shell tanks. [ABSTRACT FROM AUTHOR]

The seismic response of aboveground liquid storage tanks isolated by the proposed vertical isolation system (VIS) is investigated under near-fault and far-fault ground motions. For this purpose, a set of 14 ground motions including seven far-fault and seven pulse-like near-fault motions have been considered. Effectiveness of VIS is evaluated theoretically and numerically in selected tanks with different geometries including Short-Broad, Tall-Broad, Short-Slender, and Tall-Slender. In the proposed isolation system, the tank shell is detached from the base and supported on a ring of vertical isolators, and then the forces in the vertical direction caused by the overturning moment are isolated as an alternative to the common horizontal system used for shear base isolation of storage tanks. The equations of motion for a liquid tank equipped with the proposed system were extracted using the mass-spring simplified model of contained liquid. A study was performed by employing the non-linear solution of the governing equations and the effectiveness of the proposed system for selected tanks is discussed. To measure the effectiveness of the isolation system, the seismic response of isolated steel tanks is compared with that of the non-isolated (or fixed-base) tanks. The results of this study demonstrate the influence of the tank's geometries, characteristics of the isolation system, and input excitation features. These parameters should be reasonably selected to achieve the maximum mitigation of seismic responses in the tanks equipped with the VIS. Excitation parameters, PGV/PGA ratio of input records, and pulse period in two sets of ground motions are defined to recognize the variety of responses. It is confirmed that the VIS performs well under both near and far-fault motions but near-fault earthquakes amplify the seismic responses more than the far-fault records especially in broad tanks. [ABSTRACT FROM AUTHOR]

Cylindrical liquid storage tanks are vital lifeline structures, playing a critical role in industry and human life. Damages to these structures during previous earthquakes indicate their vulnerability against seismic events. A novel strategy to reduce the seismic demands in the structures is the use of metamaterials, being periodically placed in the foundation, called MetaFoundation (MF). The periodic configuration of metamaterials can create a stop band, leading to a decrease in wave propagation in the foundation. The aim of this paper is to study the effect of MF on the dynamic behaviour of liquid storage tanks. To that end, the governing equations of motion of the liquid storage tank equipped with MF are derived and solved in the time domain to obtain the time history of the responses under a set of ground motions. Then, the peak responses of tanks, mounted on MF, are compared with the corresponding responses in the fixed base condition. Besides, a parametric study is performed to assess the effect of the predominant frequency of earthquakes, the number of layers of metamaterials, the thickness of soft material, and the damping ratios of soft material on the performance of the MF. The obtained results indicate that the MF improves the dynamic behaviour of the squat tank, in which the mean ratio of responses using MF to the ones in the fixed base conditions equals 0.551 for impulsive displacement, overturning moment, and base shear.

Remote detection of structural aging, degradation phenomena and damage due to hazardous events is critical to ensure safety and reliability of civil or industrial structures. This is the motivation of the rapid development and increasing application of fully automated structural health monitoring (SHM) systems in civil engineering. Modal-based damage detection currently represents a popular approach for SHM of civil structures. In fact, it is a global method for damage detection and, as such, the measurement locations are not required to be close to the damage. However, damage sensitive features defined in terms of modal parameter estimates are also influenced by environmental and operational factors. Thus, neglecting this influence might jeopardize the reliability of the technology. In this framework, the present paper investigates the potential of modal-based SHM to detect earthquake damage at anchors of an atmospheric liquid storage tank. To this aim, the influences of bolt loosening at supports and of liquid level on modal parameters are investigated. The ultimate goal of the present study is the definition of criteria for the effective design and application of modal-based SHM to liquid storage tanks. [ABSTRACT FROM AUTHOR]

To deal with the effect of liquid storage on the distribution of implosion, a fluid–solid coupling model is built for the shared nodes of implosion in the liquid storage tank. The displacement compatibility and acceleration and speed coupling are achieved between the implosion field (gas, liquid) and liquid storage tank. First, using this model, the implosion-generated overpressure distribution and structural response under the working condition of half filled tank are obtained. The results show that the overpressure, displacement and stress are high on the shell near the liquid level. Then, the effects of both the TNT equivalent and liquid level on implosion in the liquid storage tank are studied. As the TNT equivalent increases, the maximum overpressure, displacement and stress on the shell near the liquid level increase. Consequently, the maximum overpressure and displacement on the shell near the liquid level exceed those at the roof-to-shell connection of the tank. In contrast, as the liquid level increases, the maximum stress and displacement first increase near the shell. After reaching the peaks near half filled level, they begin to decrease. Only when the liquid reaches a certain level, it can have an attenuating effect on the overpressure at the bottom-to-shell connection. However, if the liquid level continues to rise beyond a certain threshold, the attenuating effect is no longer prominent. [ABSTRACT FROM AUTHOR]

Purpose: Liquid storage tanks play a significant role in the industries and nuclear power plants. Soil–structure interaction (SSI) may lead to the damage and instability of such structure. Hence, the earthquake response of a cylindrical soil-supported tank is investigated using a simplified method in the time domain. Methods: The continuous liquid in the tank is lumped as convective spring–mass, impulsive spring–mass and rigid mass. The soil impedance function is modeled as the lumped-parameter system. The governing equations of motion for the coupled system under horizontal earthquake excitations are developed from the Hamilton's principle, which are solved based on the Newmark-β method. Results: Comparison studies are performed between the present results and the available results. Good agreements are observed. The variation of natural frequencies, liquid sloshing height, impulsive mass displacement, base shear and overturning moment of the tank are studied for different soil properties. Conclusion: It is concluded that the SSI effect reduces the impulsive mass displacement, the base shear and base moment; however, it has no apparent effect on the convective frequency and liquid surface wave elevation. [ABSTRACT FROM AUTHOR]

Based on potential flow theory and arbitrary Lagrangian–Eulerian method, shell–liquid and shell–wind interactions are solved respectively. Considering the nonlinearity of tank material and liquid sloshing, a refined 3-D wind–shell–liquid interaction calculation model for liquid storage tanks is established. A comparative study of dynamic responses of liquid storage tanks under wind, earthquake, and wind and earthquake is carried out, and the influences of wind speed and wind interference effect on dynamic responses of liquid storage tank are discussed. The results show that when the wind is strong, the dynamic responses of the liquid storage tank under wind load alone are likely to be larger than that under earthquake, and the dynamic responses under wind–earthquake interaction are obviously larger than that under wind and earthquake alone. The maximum responses of the tank wall under wind and earthquake are located in the unfilled area at the upper part of the tank and the filled area at the lower part of the tank respectively, while the location of maximum responses of the tank wall under wind–earthquake interaction is related to the relative magnitude of the wind and earthquake. Wind speed has a great influence on the responses of liquid storage tanks, when the wind speed increases to a certain extent, the storage tank is prone to damage. Wind interference effect has a significant effect on liquid storage tanks and wind fields. For liquid storage tanks in special environments, wind and earthquake effects should be considered reasonably, and wind interference effects cannot be ignored. [ABSTRACT FROM AUTHOR]

Abstract A numerical study of the base-isolated ground-supported cylindrical liquid storage tank is carried out using finite element method (FEM). The coupled acoustic-structural (CAS) approach in the FEM is used for the analysis of the base-isolated tanks with rigid and flexible walls with varying parameters. Base isolation systems used in the present study are laminated rubber bearing (LRB) and friction pendulum system (FPS). The effects of aspect ratio (liquid height to radius) of the tank, and the isolation time period on the seismic response of the base-isolated tank is considered for investigation. For this study, the broad and slender tanks with three different isolation time periods are considered, which exhibit their relative flexibility. The sloshing displacement, base shear, hydrodynamic pressure, and bearing displacement responses are evaluated for three-dimensional (3-D) rigid and flexible tanks subjected to bi-directional components of earthquake ground motions. Moreover, the FE results are compared with the commonly used mechanical lumped-mass model of the base-isolated tank. The results show that as the time period of the isolator increases, i.e. increased flexibility, the base shear response is considerably reduced in both the rigid and flexible, broad and slender tanks. The reduction in the impulsive component causing base shear is more as compared to the convective (sloshing) component in the base-isolated tanks. The sloshing displacement increases with increase in the time period of the base isolation systems in both the rigid and flexible tanks. The impulsive hydrodynamic pressure along the tank wall is reduced with introduction of the isolation systems and the reduction is significantly more in case of the flexible isolators. The bearing displacement increases with increase in the time period of the isolation system adopted. Highlights • Finite element (FE)-based simulations using the coupled acoustic-structural (CAS) approach for fluid-structure interaction (FSI) in tank. • Sloshing, base shear, and hydrodynamic pressures induced in 3-D ground-supported cylindrical rigid and flexible base-isolated tanks. • Bi-directional earthquake ground motion components affecting seismically base-isolated and non-isolated tanks. [ABSTRACT FROM AUTHOR]

• Based on damping principle of TMD and characteristics of liquid storage tank, a pendulum TMD (PTMD) is proposed. • Seismic performance of the hybrid control system with base-isolation and PTMD is analyzed. • Influence laws of PTMD mass ratio and base-isolation period on dynamic responses are discussed. • Base-isolation with PTMD has a significant damping effect on seismic responses of liquid storage tank. It is necessary to ensure the safety of liquid storage tanks under earthquakes, but the damage probability of the non-damping liquid storage tanks is higher under earthquakes. Based on the damping principle of tuned mass damper (TMD) and the characteristics of the liquid storage tank, a new pendulum TMD (PTMD) system is proposed. Considering the material nonlinearity, the fluid–structure interaction and liquid sloshing characteristics, the three-dimensional numerical calculation models of the non-damping, PTMD, base-isolation (BI) and BI-PTMD liquid storage tanks are established, respectively. The seismic responses of different types of liquid storage tanks under the action of near-field pulse-like earthquakes are investigated, the damping performance of the hybrid control system with the isolation and the PTMD is analyzed, and the influence laws of the mass ratio of PTMD-structure and base-isolation period on the dynamic responses of the liquid storage tanks are discussed. The results show that the BI-PTMD hybrid control system has a significant damping effect on the seismic responses of the liquid storage tank. The damping rate of the base shear is the largest, reaching 86.0%, and the control rate of the PTMD on the displacement of the isolation layer is about 20.0%. The hoop stress, effective stress, liquid pressure and displacement of isolation layer decrease with the increase of the mass ratio of PTMD to structure. With the increase of base-isolation period, the hoop stress, axial compressive stress, effective stress and liquid pressure decrease, and the control effect of PTMD on the liquid storage tank is weakened. [ABSTRACT FROM AUTHOR]

A simplified model of a rectangular liquid storage tank is proposed to estimate the earthquake responses of the system while considering the effects of fluid-structure interactions. The complicated three-dimensional structural behavior of a rectangular tank is represented by the simple combination of the fundamental modes of a rectangular-ring-shaped frame structure and a cantilever beam. The governing equation for the system is derived from Lagrange's equation. The earthquake responses of deflection, hydrodynamic pressure and its resultant force and moment, base shear and overturning moment due to the structural deformation are obtained from the solution of the governing equation. The effective masses of the system and their heights are presented with the effective added masses and their heights from the hydrodynamic effects. The total earthquake responses are obtained with the convective earthquake responses taken into consideration. The proposed simplified model is applied to example rectangular liquid storage tanks with various aspect ratios, and the accuracy of the model is demonstrated. The proposed simplified model can be employed for the seismic design of a rectangular liquid storage tank, and reliable estimations for earthquake responses of the considered fluid-structure interaction system are obtained without sophisticated and/or complicated dynamic analysis. • Simple model for earthquake response analysis of a rectangular liquid storage tank. • Estimation of earthquake responses considering fluid-structure interaction effects. • Derivation of a governing equation with an approximated fundamental mode. • Effective masses and their heights to estimate earthquake responses. • Verification of the proposed simplified model for a rectangular liquid storage tank. [ABSTRACT FROM AUTHOR]

Large capacity tanks storing various liquids are important components in distribution and transmission systems. During operation tanks can be subjected to different types of loading. Therefore, maximum attention must be paid to the tank design to capture all possible causes and forms of failures. The article deals with the procedure for seismic resistance of liquid storage tanks which are in accordance with the principles of Eurocode 8 standard. The seismic analysis is performed on flexible (steel) circular vertical ground-supported model of tank containing liquid (water). The main aim is to determine basic seismic characteristics, distributions of hydrodynamic pressure, dynamic properties and response of investigated tank-liquid system subjected to earthquake excitation (El Centro). Seismic analysis and results comparison are carried out on mechanical spring-mass model (Eurocode 8) and finite element model (ANSYS).

The occurrence of excessive fluid sloshing during an earthquake can damage structures used to store fluids and can induce secondary disasters, such as environmental destruction and human casualties, due to discharge of the stored fluids. Thus, to prevent such disasters, it is important to accurately predict the sloshing behavior of liquid storage tanks. Tubular level gauges, which visually show the fluid level of a liquid storage tank, are easy to install and economical compared to other water level gauges. They directly show the fluid level and can be applied for various fluids because they can be constructed with various materials according to the fluid characteristics and the intended use. Therefore, in this study, the shaking table test was conducted to verify the validity of the method for measuring the water level response of the tubular level gauge installed on a liquid storage tank using image signals. In addition, image enhancement methods were applied to distinguish between the float installed in the tubular level gauge and the gray level of the background.

Employing base isolation technique for reduction of seismic response of liquid storage tanks has been proved to be quite effective. The main purpose of this paper is to quantitatively clarify, the contribution of convective and impulsive parts of the contained liquid in seismic behavior of an isolated liquid tank. Moreover, the accuracy of the simplified model which is generally used for the prediction of seismic behavior of conventional tanks is examined for isolated liquid tanks. For these purposes, the seismic response of the isolated cylindrical liquid storage tanks is considered using both the exact finite element model and simplified mass-spring model. The fluid–structure interaction is considered in finite element model. The comparison of the results obtained from two models shows that unlike conventionally constructed tanks, the contribution of convective mass cannot be neglected for seismically isolated tanks. Moreover, the accuracy of the simplified model for evaluating the main design parameters including base shear, global overturning moment, and sloshing height is examined for various tank dimensions and earthquake ground motions. The difference between the base shear and overturning moment results in the FE model and the simplified model of an isolated tank limited to 10%. It approves that the simplified mechanical models can be used with confidence for evaluating the seismic design parameters of various isolated tanks. However, the free surface displacement cannot be accurately predicted by simplified models, especially for medium and broad tanks. [ABSTRACT FROM AUTHOR]

Abstract Three-dimensional (3-D) ground-supported cylindrical and rectangular rigid liquid storage tanks filled with water and subjected to seismic base excitation are investigated using finite element method (FEM). The analyses of the tanks are carried out using coupled acoustic-structural (CAS) and coupled Eulerian-Lagrangian (CEL) approaches of the FEM using Abaqus®. The CAS approach based on linear wave theory and the CEL approach based on non-linear wave theory are used here to study the fluid-structure interaction (FSI) behavior of the tanks. Sloshing displacement, impulsive, convective, and total hydrodynamic pressures are investigated for varying geometries of the tanks. The small amplitude sloshing and hydrodynamic pressure responses are compared between the two FE-based, CAS and CEL approaches. The results obtained from the present FE-based analysis approaches are found to be in close agreement with the experimentally obtained seismic response in the 3-D cylindrical and rectangular tanks subjected to seismic ground motions. The ratio of peak sloshing height (h) to liquid height in the tank (H L) obtained in the cylindrical tank using the CAS approach is 0.0425 and that by the CEL is 0.039, whereas for rectangular tank it is 0.060 by the CAS approach and 0.046 by the CEL approach; thereby, signifying relatively small sloshing amplitude response. It is concluded that the non-linearity of the sloshing wave displacement does not play a significant role while calculating the hydrodynamic pressure distribution on the rigid tank walls. Highlights • FE simulations by coupled acoustic-structural (CAS) and coupled Euler-Lagrange (CEL). • Small amplitude sloshing displacement and hydrodynamic pressures in rigid tanks. • Dynamic analysis of cylindrical and rectangular rigid tanks for seismic excitations. [ABSTRACT FROM AUTHOR]

This paper introduces an improved isolation system for aboveground storage tanks (ASTs). In this system, the tank shell is supported by a ring of vertical isolation systems (VIS) that dampen the rocking motion of the tank shell caused by dynamic loads. On the other hand, the forces in the vertical direction caused by the overturning moment are isolated as an alternative to the common horizontal system used for shear base isolation of ASTs. The effects of the proposed vertical isolation system on the seismic responses of the contained liquid are examined using various tank dimensions and earthquake ground motions. The finite element model (taking into account fluid-structure interaction effects) is used to simulate the contained liquid, as well as the tank shell. The results indicate that the new system could efficiently reduce the main seismic design parameters of the tanks, including base shear, overturning moment, and seismic stress in the tank shell. The sloshing wave height, however, is not significantly affected. [ABSTRACT FROM AUTHOR]

A typical viable technique to decrease the seismic response of liquid storage tanks is to isolate them at the base. Base-isolation systems are an efficient and feasible solution to reduce the vulnerability of structures in high seismic risk zones. Nevertheless, when liquid storage tanks are under long-period shaking, the base-isolation systems could have different impacts. These kinds of earthquakes can damage the tanks readily. Hence, the seismic behaviour and vibration of cylindrical liquid storage tanks, subjected to earthquakes, is of paramount importance, and it is investigated in this paper. The Finite Element Method is used to evaluate seismic response in addition to the reduction of excessive liquid sloshing in the tank when subjected to the long-period ground motion. The non-linear stress-strain behaviour pertaining to polymers and rubbers is implemented while non-linear contact elements are employed to describe the 3-D surface-to-surface contact. Therefore, Nonlinear Procedures are used to investigate the fluid-structure interactions (FSI) between liquid and the tank wall while there is incompressible liquid. Part I, examines the effect of the flexibility of the isolation system and the tank aspect ratio (height to radius) on the tank wall radial displacements of the tank wall and the liquid sloshing heights. Maximum stress and base shear force for various aspect ratios and different base-isolators, which are subjected to three seismic conditions, will be discussed in Part II. It is shown that the composite-base isolator is much more effective than other isolators due to its high flexibility and strength combined. Moreover, the base isolators may decrease the maximum level pertaining to radial displacement. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Based on potential flow theory and arbitrary Lagrangian−Eulerian method, shell−liquid and shell−wind interactions are solved respectively. Considering the nonlinearity of tank material and liquid sloshing, a refined 3-D wind−shell−liquid interaction calculation model for liquid storage tanks is established. A comparative study of dynamic responses of liquid storage tanks under wind, earthquake, and wind and earthquake is carried out, and the influences of wind speed and wind interference effect on dynamic responses of liquid storage tank are discussed. The results show that when the wind is strong, the dynamic responses of the liquid storage tank under wind load alone are likely to be larger than that under earthquake, and the dynamic responses under wind−earthquake interaction are obviously larger than that under wind and earthquake alone. The maximum responses of the tank wall under wind and earthquake are located in the unfilled area at the upper part of the tank and the filled area at the lower part of the tank respectively, while the location of maximum responses of the tank wall under wind−earthquake interaction is related to the relative magnitude of the wind and earthquake. Wind speed has a great influence on the responses of liquid storage tanks, when the wind speed increases to a certain extent, the storage tank is prone to damage. Wind interference effect has a significant effect on liquid storage tanks and wind fields. For liquid storage tanks in special environments, wind and earthquake effects should be considered reasonably, and wind interference effects cannot be ignored.

Liquid storage tanks are among vital infrastructures, and their seismic vulnerability assessment plays a pivotal role in uninterrupted operation of an industrial plant. Technically, vulnerability notion relates capacity of each tank component's resistance to failure subjected to different seismic hazard levels. The predominant source of damage to liquid-containing tanks is steel shell buckling which can be intensified by base flexibility of fully anchored tanks. This flexibility is mainly resulted from anchor bolt failure and base concrete damage. In other words, the presence of anchors does not necessarily preclude anchorage failure or loss of concrete support, especially during large earthquake events. A case study on a liquid storage tank is introduced in this paper to highlight the influence of base flexibility on the seismic performance of fully anchored tanks. The tank is initially designed in accordance with the requirements of American Petroleum Institute, API-650. Fluid-structure interaction (FSI) is simulated by means of so-called added-mass approach. Two sets of finite element models are constructed, namely; fixed base (FB) and flexible base (FLB) tank. Nonlinear time history analysis based on a suite of twenty-two multi-directional spectrally matched acceleration time histories are conducted. Simultaneous input motions of two horizontal components are of particular importance as they shift the position of failure mechanism to directions being more affected by combined accelerations. Critical intensity measures (IMs) according to incremental dynamic analysis are then determined. Fragility curves are obtained by introducing conditional probability of failure as a function of critical IM. Results reveal that modelling base flexibility may contribute to lower value of critical IMs compared to that obtained from restrained support model. More specifically, FLB model demonstrates lower value of endurable peak ground acceleration (PGA) compared to the initial value selected for the tank design as per API requirements. [ABSTRACT FROM AUTHOR]

This paper proposes a dynamic centrifuge model test method for the accurate simulation of the behaviours of a liquid storage tank with different types of foundations during earthquakes. The method can be used to determine the actual stress conditions of a prototype storage-tank structure. It was used in the present study to investigate the soil-foundation-structure interactions of a simplified storage tank under two different earthquake motions, which were simulated using a shaking table installed in a centrifuge basket. Three different types of foundations were considered, namely, a shallow foundation, a slab on the surface of the ground connected to piles and a slab with disconnected piles. The test results were organised to compare the ground surface and foundation motions, the slab of foundation and top of structure motions and the horizontal and vertical motions of the slab, respectively. These were used to establish the complex dynamic behaviours of tank models with different foundations. The effects of soil-foundation-structure interaction with three foundation conditions and two different earthquake motions are focused and some important factors, that should be considered for future designs are also discussed in this research. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]