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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]

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]

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. [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]

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.

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]

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]

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]

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]

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]

This article presents a multi dynamic absorber for suppressing liquid sloshing in a floating roof tank. The presented multi dynamic absorber uses U-tubes set on the floating roof. Many seismic damages on floating roof tanks by the sloshing of the contained liquid in the tank due to long periodic components of earthquake were reported. Since the natural period of sloshing varies according to the liquid height, robustness for parameters variances such as natural period is required for the sloshing suppression device to obtain a good performance. From this point of view, a multi dynamic absorber is developed instead of the single dynamic absorber which is sensitive to the parameter variance. A multi degree of freedom mechanical model for sloshing of the contained liquid and the presented multi dynamic absorber on the floating roof of the tank is derived to design the optimal tuning and optimal damping for parameters of the multi dynamic absorber and to evaluate the sloshing suppression performance. Numerical simulations on two kinds of actual size floating roof tank are conducted to examine seismic response of the present device as well as the transfer function characteristics. As the result the presented multi dynamic absorber is effective to suppress the sloshing of the floating roof.

The seismic isolation of ground-supported cylindrical liquid storage tank using the newly developed oblate spheroid base isolation (OSBI) system is investigated. The OSBI is an ellipsoidal-shaped isolator in both of its horizontal axes and dissipates seismic input energy in rolling friction apart from period lengthening achieved through the oblateness. The detailed mathematical formulation and governing dynamical equations of motion for a tank mounted on the non-linear OSBI are derived and analyzed using the numerical integration technique to unravel the underlying mechanics behind its dynamic behavior. An idealized mechanical model of the tank consists of three-lumped masses: convective, impulsive, and rigid. The dynamic responses are investigated for the tank subjected to uni-directional sinusoidal harmonic motion as well as to five time-varying, bi-directional horizontal components of earthquakes. The seismic response of the liquid storage tanks with the OSBI system is compared with that of the same tank either isolated using pure-friction (P-F) system or kept non-isolated. In order to understand the dynamic behavior of the tank mounted on the OSBI system, the influence of different isolator parameters such as eccentricity, coefficient of rolling friction, and aspect ratio of the tank are studied. The energy responses are also evaluated to assess the performance of the OSBI system. From the present study, it is found that the OSBI system is effective in mitigating the seismic response in the liquid storage tanks. • Mechanics of rolling isolation system for tanks on patented - highly non-linear oblate spheroid base isolation (OSBI) system. • OSBI system eccentricity, rolling friction, and aspect ratio of ground-supported cylindrical tank affecting seismic response. • Dynamics of tank under uni-directional sinusoidal harmonic base excitation and bi-directional components of real earthquakes. • Seismic input and recoverable energy formulations to evaluate OSBI in vibration control for different aspect ratios of tank. • Mathematical equations derived to model mechanics of OSBI for fluid-solid interaction dynamical system. [ABSTRACT FROM AUTHOR]

The article investigates the seismic response of a cylindrical liquid storage tank under tri-directional components of earthquake ground motions using coupled-structural finite element simulation. The study describes the tank modeling of the interaction, examines the time history responses of sloshing displacement and base shear and compares these with the bi-directional horizontal components of the earthquake ground motions. It also observes the hydrodynamic pressure distribution.

In thispaper, the effects of a rigid baffle on the seismic response of liquid in a rigid cylindrical tank are evaluated. A baffle is an annular plate which supplies a kind of passive control on the effects of ground excitation. The contained liquid is assumed incompressible, inviscid and has irrotational motion. To estimate the seismic response, the method of superposition of modes has been applied. To analyze the rigid tank response, Laplace's equation is considered as the governing equation of the fluid domain, in both time and frequency domains. The boundary element method (BEM) is employed to evaluate the natural modes of liquid in a cylindrical tank. To gain this goal, the fluid domain is divided into two upper and lower parts partitioned by the baffle. Linearized kinematic and dynamic boundary conditions of the free surface of the contained liquid have been considered. [ABSTRACT FROM AUTHOR]

In order to reduce the seismic response of storage tanks under the earthquake, the base of ring beam structure is designed as a parallel isolation structure system with the slipping and the rubber isolation support. The convection and liquid -- solid coupling vibration are considered as a non -- coupled multi -- particle system. Depending on the judgment boundary whether the base shearing force is bigger than the yield shearing force or not, the seismic response of the tanks with the slipping and the rubber isolation support is analyzed by the Newmark-β method, considering the parameters of different seismic intensities, different friction coefficients, different total load ratios of the parallel isolation support structure, different locations, different ratios of height to diameter, different isolation periods and equivalent damping ratios. Results indicate that the base shearing forces of the tank are decreased obviously, and the rocking wave height is increased lightly under definite design parameters after isolation. Different parameters result in different isolation effects, thus the parameter design needs to be optimized. [ABSTRACT FROM AUTHOR]

The response of liquid storage tanks isolated by the sliding systems is investigated under two horizontal components of real earthquake ground motion. The continuous liquid mass is lumped as convective mass, impulsive mass and rigid mass. The corresponding stiffness associated with these lumped masses is calculated depending upon the properties of the tank wall and liquid mass. The governing equations of motion of the tank with a sliding system are derived and solved by Newmark''s step-by-step method with iterations. The frictional forces mobilized at the interface of the sliding system are assumed to be velocity dependent and their interaction in two horizontal directions is duly considered. A parametric study is also conducted to study the effects of important system parameters on the effectiveness of seismic isolation of the liquid storage tanks. The various parameters considered are (i) the period of isolation (ii) the damping of isolation bearings and (iii) the coefficient of friction of sliding bearings. It has been found that the bi-directional interaction of frictional forces has noticeable effects and if these effects are ignored then the sliding base displacements will be underestimated which can be crucial from the design point of view. Further, the dependence of the friction coefficient on relative velocity of the sliding bearings has no significant effects on the peak response of the isolated liquid storage tanks. [Copyright &y& Elsevier]

The inappropriate performance of liquid storage tanks following devastating earthquakes indicates that the tank damage could lead to catastrophic consequences. As the rocking response of unanchored tanks plays a significant role in their seismic performances, the base anchorage is an essential element to control the seismic performance of on-ground tanks. The present study focuses on the effect of anchorage systems, as the retrofitting strategy, on the seismic performance of an existing unanchored tank damaged during the Silakhor Earthquake of 2006 in Iran. To this end, regular steel and shape memory alloy (SMA) anchor bolts were utilized. The Seismic performance of the tank was evaluated before and after retrofitting. For every retrofitted tank, different configurations of anchor bolts were considered. The seismic performance of tanks has been investigated using incremental dynamic analysis (IDA) analysis. To assess the seismic performance of every case, a fragility analysis was conducted. The results revealed that anchored tanks showed better seismic performance compared to unanchored ones. It was also shown that the combination of energy dissipation and the super-elastic behavior of SMA anchors leads to a considerable reduction in shell failure and damage to the anchorage system. • The seismic performance of a buckled liquid storage tank during a natural earthquake was investigated. • Two types of anchor bolts (regular steel and SMA) were utilized to retrofit of the tank. • A parametric study was conducted to assess the effectiveness of the above retrofitting strategies. • A fragility based buckling assessment was performed to compare the seismic performance of the tank. • Results revealed the appropriate performance of the SMA-type anchor bolts. [ABSTRACT FROM AUTHOR]

Motivated by the seismic response of unanchored liquid storage tanks, their uplift mechanism under strong lateral loading is examined. Using three-dimensional finite element models, nonlinear static analysis is conducted to define the moment-rotation relationship of uplifting tanks resting on rigid foundation and describe the evolution of critical response parameters with increasing level of lateral loading. Meridional and hoop stress, as well as their distribution and evolution with increased uplift are computed. Comparing the numerical results with the corresponding results from anchored tanks, striking differences are observed on the values of compressive meridional stresses and their distribution around the tank circumference. Cyclic analysis, associated with repeated uplift at both sides of the tank, is also performed, to obtain the corresponding hysteretic response and verify the assumption of nonlinear-elastic tank behaviour, used in several previous works. Finally, an analytical solution is developed, capable of describing tank uplift in an efficient manner. The analytical solution accounts for the special features of uplift, obtained from the finite element solution, and can be used for simple and reliable assessment of seismic performance in unanchored liquid storage tanks. • The response of liquid storage tanks under earthquake loading is examined. • Monotonic and cyclic nonlinear analysis are performed via 3D finite element models. • The evolution of critical engineering demand parameters is presented. • Special attention is paid to the meridional stress compression zone. • An analytical solution is developed in view of simplified performance assessment. [ABSTRACT FROM AUTHOR]

Earthquake performance of liquid storage tanks may be substantially improved by base-isolation. However, the possibility of facing large isolator displacements in case of large magnitude near-fault earthquakes threatens the safety of these structures, which may be realized if the period of the velocity pulses that typically exist in the near-fault earthquake records are close to their isolation periods. Increasing isolation system characteristic strength may help reducing the aforementioned large isolator displacements but this in turn may have a negative impact on the superstructure response. Therefore, this study aims to investigate the influence of the characteristic strength of the isolation system on the behavior of base-isolated liquid storage tanks under representative historical near-fault and far-fault earthquakes by making use of a set of benchmark tank models with different levels of isolation system characteristic strength ratios. Numerical modeling and non-linear time history analyses are carried out via the academic software 3DBASIS-ME,which offers the possibility of conducting such modeling and analysis following a highly preferred mechanical analog that is able to take the deformability of the tank wall and sloshing of the fluid into account by considering the fundamental sloshing and fundamental fluid-tank modes of vibration as single degree of freedom systems sharing a common isolation base-mat. The seismic responses including isolation system displacement, sloshing fluid displacement, isolation system shear force, fluid-tank shear force, and sloshing fluid shear force are reported in a comparative manner. Results show that while higher characteristic strength effectively reduces large base displacements observed under near-fault earthquakes, it may cause significant amplifications in the superstructure responses particularly under far-fault earthquakes. [ABSTRACT FROM AUTHOR]