Vertical Isolation Research Articles

Vertical equipment isolation using piezoelectric inertial-type isolation system

Among anti-seismic technologies, base isolation is a very effective means of mitigating damage to structural and nonstructural components, such as equipment. However, most seismic isolation systems are designed for mitigating only horizontal seismic responses because the realization of a vertical isolation system (VIS) is difficult. The difficulty is primarily due to conflicting isolation stiffness demands in the static and dynamic states for a VIS, which requires sufficient rigidity to support the self-weight of the isolated object in the static state, but sufficient flexibility to lengthen the isolation period and uncouple the ground motion in the dynamic state. To overcome this problem, a semi-active VIS, called the piezoelectric inertia-type vertical isolation system (PIVIS), is proposed in this study. PIVIS is composed of a piezoelectric friction damper (PFD) and a leverage mechanism with a counterweight. The counterweight provides an uplifting force in the static state and an extra inertial force in the dynamic state; therefore, the effective vertical stiffness of PIVIS is higher in the static state and lower in the dynamic state. The PFD provides a controllable friction force for PIVIS to further prevent its excessive displacement. For experimental verification, a shaking table test was conducted on a prototype PIVIS controlled by a simple controller. The experimental results well agree with the theoretical results. To further investigate the isolation performance of PIVIS, the seismic responses of PIVIS were simulated numerically by considering 14 vertical ground motions with different characteristics. The responses of PIVIS were compared with those of a traditional VIS and a passive system (PIVIS without control). The numerical results demonstrate that compared with the traditional and passive systems, PIVIS can effectively suppress isolation displacement in all kinds of earthquake with various peak ground accelerations and frequency content while maintaining its isolation efficiency. The proposed system is particularly effective for nearfault earthquakes with long-period components, for which it prevents resonant-like motion.

Horizontal-Vertical-Rocking Coupled Response Analysis of Vertical Seismic Isolated Structure under Near-Fault Earthquakes

For vertical isolated structures with excessive vertical eccentricity for mass and vertical stiffness, horizontal-vertical-rocking response needs to be better understood for vertical isolated structures located in near-fault areas, where long-period velocity pulse can be produced. In this study, a seismic isolation system including quasizero stiffness (QZS) and vertical damper (VD) is used to control near-fault (NF) vertical earthquakes. The responses of horizontal-vertical-rocking coupling base-isolated structure including quasizero stiffness (QZS) and vertical damper (VD) subjected to NF horizontal and vertical ground motions are investigated. Nonlinear dynamic analyses are conducted to study the effects of essential parameters such as isolation system eccentricity, static equilibrium position, vertical isolation period, and vertical damping ratio on seismic responses of vertical isolated structure. It is found that increasing vertical period and damping ratio causes the vertical isolated structures to behave well in reducing rocking responses of structure. The effect of horizontal-vertical-rocking coupling on vertical seismic isolation efficiency is insignificant. The vertical seismic isolation remains effective as compared to the system supported on rubber bearings. The vertical damping can significantly control the vertical displacement and rocking moment.

Multilayered epoxy composites by a macroscopic anisotropic design strategy with excellent thermal protection

Controlling thermal anisotropy structure is important for emerging heat management applications such as thermal shield, thermal camouflage, and heat concentration. In this work, alternating stack epoxy composites (AECs) are prepared, inspired by the multilayer structure of an onion. Hexagonal boron nitride (h-BN) and expanded vermiculite (E-ver) are used as fillers in epoxy resin (Epon), taking as heat-dissipation layers and heat-insulation layers, respectively. Vertical heat isolation and local hotspot protection are endowed by the effective structural design. The temperature rise time of top surface is delayed by 404.2%, and the stabilized temperature is reduced by 10–15 °C (the bottom is heated to 120 °C); meanwhile, the whole composites are heated to 80 °C with good heat-dissipation performance, compared with those of homogeneous materials. There are two thermal phenomena synergistically in the anisotropy structure: excellent thermal protection when heating and good heat dissipation when cooling. Further, a thermal transfer mechanism of heat insulation and heat dissipation is analyzed based on numerical simulation and experiment. The multilayer epoxy composites are promising for the development of high-performance thermal products such as heat spreader, equipment cooling, and thermal hose.

Torsional response reduction of plan-asymmetric vertical seismic isolation by appropriate distribution of viscous and viscoelastic dampers

In this article, torsional control has been studied in the plan-mass asymmetric vertical seismic isolation (VSI) system considering the three-dimensionally analytical model. In the 3D VSI, a structure is partitioned by vertical isolation planes into two inner and outer substructures interconnected by links for lateral response reduction. In an ideal analytical model of plan-mass asymmetric VSI, plan-wise distribution of damping and stiffness have been provided for more torsional control. Seismic responses of the non-classically 3D VSI were obtained by Runge-Kutta numerical method, considering a large number of isolation ratios. In this investigation, the mass and stiffness ratios of substructures are defined with respect to the original structure which provides a novel method of graphic presentation for analysis results. In this manner, contour graphs create comprehensive and worthwhile insight into the 3D VSI behavior and can also serve as a design tool for the preliminary design of the system. The results show that in the case that the inner substructure is the flexible one, torsional control is nearly effective in both substructures satisfactorily, regardless of plan-wise damping distribution. However, in the second case that is the outer flexible substructure, torsional control is nearly effective in the stiff substructure while the response in flexible substructure is satisfactory just in a limited range of isolation ratios.

COVID-ABS: An agent-based model of COVID-19 epidemic to simulate health and economic effects of social distancing interventions.

The COVID-19 pandemic due to the SARS-CoV-2 coronavirus has directly impacted the public health and economy worldwide. To overcome this problem, countries have adopted different policies and non-pharmaceutical interventions for controlling the spread of the virus. This paper proposes the COVID-ABS, a new SEIR (Susceptible-Exposed-Infected-Recovered) agent-based model that aims to simulate the pandemic dynamics using a society of agents emulating people, business and government. Seven different scenarios of social distancing interventions were analyzed, with varying epidemiological and economic effects: (1) do nothing, (2) lockdown, (3) conditional lockdown, (4) vertical isolation, (5) partial isolation, (6) use of face masks, and (7) use of face masks together with 50% of adhesion to social isolation. In the impossibility of implementing scenarios with lockdown, which present the lowest number of deaths and highest impact on the economy, scenarios combining the use of face masks and partial isolation can be the more realistic for implementation in terms of social cooperation. The COVID-ABS model was implemented in Python programming language, with source code publicly available. The model can be easily extended to other societies by changing the input parameters, as well as allowing the creation of a multitude of other scenarios. Therefore, it is a useful tool to assist politicians and health authorities to plan their actions against the COVID-19 epidemic.

A new electric wheel and optimization on its suspension parameters

Hub-driven technology with its many advantages has become a potential transformation technology in the automotive industry. In order to inhibit the negative effects of the in-wheel motor, a new electric wheel configuration was presented with two-stage suspensions, and optimization was conducted for the suspension parameters. With the specially introduced flexible transmission elements and motor suspension, the electric wheel is capable of achieving power transmission and vertical vibration isolation simultaneously. A quarter-vehicle model was established, and vehicle performance-related indices were defined to evaluate the applicability of the new electric wheel. An optimization problem was then constructed for suspension parameters, where constraint conditions were derived according to vehicle dynamics. The optimal solution was sought by a genetic algorithm, aiming at utilizing the full potential of the configuration. Simulations were carried out taking the optimal suspension parameters into account, and comparison was made with vehicles equipped with other electric wheel configurations in terms of these performance indices. The results show that the proposed electric wheel reduces motor vibration, and increases wheel dynamic load and vehicle body acceleration.

Investigations on a vertical isolation system with quasi-zero stiffness property

This paper presents a series of experimental and numerical investigations on a vertical isolation system with quasi-zero stiffness (QZS) property. The isolation system comprises a linear helical spring and disk spring. The disk spring is designed to provide variable stiffness to the system. Orthogonal static tests with different design parameters are conducted to verify the mathematical and mechanical models of the isolation system. The deviations between theoretical and test results influenced by the design parameters are summarized. Then, the dynamic tests for the systems with different under-load degrees are performed, including the fast sweeping tests, harmonic excitation tests, and half-sine impact tests. The displacement transmissibility, vibration reduction rate, and free vibration response are calculated. Based on the test results, the variation of the transmission rule is evaluated and the damping magnitudes and types are identified. In addition, the relevant numerical time history responses are calculated considering the nonlinear behavior of the system. The results indicate that the QZS isolation system has a satisfactory isolation effect, while a higher damping level can potentially promote the isolation performance in the low-frequency range. It is also proved that the numerical calculation method accurately predicts the transmission character of the isolation system.

A novel device for a vertical rocking isolation system with uplift allowed for industrial equipment and structures

In this paper, a novel device called the “ISO3D-2G” is proposed for a three-dimensional vertical rocking isolation (VRI) system. The VRI system works by isolating critical vibration sources, e.g., earthquake events and operational high-frequency vibrations. In this work, only its performance as a seismic isolation system is studied. The ISO3D-2G is made of a steel structure and an elastomeric rubber system, offering improved properties as compared to previous versions of the device. The device is manufactured at a full scale and is experimentally tested. To represent the vertical non-linear hysteretic behavior of the device, a numerical model called the hyperelastic Bouc-Wen (HBW) model is developed. The HBW model combines a hyperelastic component (represented in this work by a third-order Ogden model) and a hysteretic component (represented by a modified BW model). The simply supported horizontal behavior of the device is represented through a non-linear 2D frictional hysteretic model. The HBW model is calibrated to fit the experimental data obtained in the test, and guidelines are provided for understanding and manually calibrating the model. The dynamic performance of the system is analyzed using time-history analyses with four records (three non-impulsive records and one impulsive record). Equations are presented for the motion of the system. For the three non-impulsive seismic records, the observed behavior was similar to that in conventional lateral isolation systems. Horizontal force reduction ratios between 7.4 and 10.9 were obtained. The maximum shear base remained below 23% of the total weight of the structure, even considering the three components of the ground motion. In addition, vertical force reduction ratios between 2 and 3.8 were obtained, demonstrating that the vertical isolation effect was satisfactory. However, for an impulsive seismic record, there was a significant change in the patterns of behavior, owing to the significant uplift of two of the four devices. Despite this, the structure remained stable, and the lateral isolation effect was preserved. Finally, it was concluded that using vertically flexible devices with high damping in the base of structures to generate a rocking isolation mechanism is an effective approach to reducing the seismic demand, even though the isolated modes of the structure do not take periods longer than 2.0 s. Although there was no lateral translation at the base, the VRI system isolated the structure by allowing lateral and vertical displacement of the center of mass.

Seismic performance analysis of a large-scale single-layer lattice dome with a hybrid three-directional seismic isolation system

A large number of studies and applications have been carried out on horizontal seismic isolation systems, and their effectiveness has been indicated. For long-span spatial structures, vertical seismic load plays an important role. However, vertical seismic isolation technology has not been extensively investigated. In this paper, a hybrid bearing with three-directional seismic isolation effects is proposed, in which the triple friction pendulum component and the viscous damping component are combined in series. Compared with other seismic isolation systems, the advantages of this hybrid seismic isolation system are that it can not only greatly lengthen the structural periods but also dissipate the seismic energy in all three directions. A hybrid numerical modeling method for this hybrid seismic isolation bearing is also developed. The seismic performance of a welded large-scale single-layer lattice dome with this hybrid seismic isolation system subjected to near-field ground motions is analyzed. The results show that the important dynamic demands in the dome are significantly suppressed compared with the base-fixed dome. The seismic isolation effects are evaluated in all three directions, and the effectiveness of the hybrid isolation system is verified. Finally, a comparative study is performed, and the mechanical parameters of this hybrid bearing are discussed. It is found that the damping energy dissipation in the seismic isolation bearings is not the most important factor in reducing structural dynamic demands. The proposed seismic isolation system and its numerical modeling method provide an attractive and effective alternative for the design of long-span spatial structures with hybrid seismic isolation systems.

Compressive behavior of low shape factor lead-rubber bearings: Full-scale testing and numerical modeling

Low shape factor lead-rubber bearings, defined as bearings with relatively thick rubber layers, have been confirmed by several studies to be feasible for vertical seismic isolation because of their flexibility in the vertical direction. However, information on various behavior aspects of low shape factor lead-rubber bearings remains inadequate. With much greater vertical deformation under working conditions than conventional high or medium shape factor bearings, low shape factor lead-rubber bearings display certain unique mechanical behaviors due to the nonlinearity and inelasticity of lead plugs. The applicability of existing design equations to the compressive stiffness of low shape factor bearings remains unknown. Although it has been demonstrated that the axial load has an insignificant effect on the compressive stiffness of lead-rubber bearings with high or medium shape factors, few studies have referred to the influence of the axial load on the vertical stiffness of low shape factor bearings. To investigate the unique compressive behavior of the low shape factor lead-rubber bearings, bearings with various shape factors were tested under various axial loads to compare their compressive behavior in terms of compressive stiffness and force-displacement relationships. The obtained results indicate that the existing design formula for compressive stiffness is not applicable for lead-rubber bearings with a shape factor lower than 11. Although the axial load has a minor influence on the compressive stiffness of lead-rubber bearings with high shape factors, it has a non-negligible influence on that of low shape factor bearings. In addition, a unique behavior characterized by hardening in compressive stiffness is found in the force-displacement relationships of the bearings. Numerical models were developed and calibrated with the experimental results. A parametric study of the numerical models shows that the hardening phenomenon is caused by sliding between the lead-steel interfaces and the lead-rubber interfaces. This sliding decreases the vertical stiffness and reduces the energy dissipation of the bearings. An increase in the coefficient of friction between the interfaces can increase the compressive stiffness of bearings with relatively high shape factors, but bearings with low shape factors are insensitive to the friction coefficients.

Structural analysis and tectonic evolution of the Komombo basin, south Egypt; an example of interior Cretaceous rift

Structural geometry of the Komombo basin was demonstrated using 2D seismic data. Komombo basin appears as two, left-stepping, en-echelon half grabens separated by a NNE oriented broad anticline dissected by NNE oriented oblique-slip faults. The developed fault pattern in the Komombo basin is a typical, non-collinear fault system which encompasses several segments of NW, N–S and WNW orientations. Komombo basin shows along strike variation in the fault pattern. Its southern part is further subdivided into several intrabasinal troughs and highs bounded by synthetic down-dip and antithetic up-dip fault systems, while the northern part is characterized by a synthetic SW dipping step fault pattern producing small eastward rotated half-grabens. The two fault patterns are separated by N–S shear zone.The architecture of the Komombo basin is developed through two extensional phases. The first phase occurred during the Barressian- Hautervian (a NE-SW directed extension), producing predominantly NNW-SSE to NW oriented normal faults. The first phase was followed by a tectonically quiescent period during Barremian-Early Aptian. The rifting resumed during Late Aptian-Late Albian (phase II) under similar stress condition. A group of small NW oriented faults were developed during the second phase as indicated by Late Aptian-Late Albian growth in their hanging walls.The seismic reflection data and D-z graph display dip-linkage between the NW oriented faults that developed during the two rift phases. The Late Aptian-Late Aptian fault system nucleated in a vertical isolation from the Barressian-Hautervian fault system as indicated by the displacement minima observed at the Late Barremian-Early Aptian thick shale.

Evaluating adaptive vertical seismic isolation for equipment in nuclear power plants

Seismic isolation systems are widely recognized as beneficial for protecting both acceleration- and displacement-sensitive nonstructural systems and components. So-called adaptive isolation systems exhibit nonlinear characteristics that enable engineers to achieve various performance goals at different hazard levels. These systems have been implemented to control the horizontal response, but there has been limited research on seismic isolation for controlling the vertical response. Thus, this paper seeks to evaluate the merits of adaptive vertical isolation systems for components, specifically in nuclear power plants (NPPs). To do this, six vertical isolation systems are designed to achieve multiple goals. The systems consist of in-parallel configurations of linear and nonlinear springs and dampers, falling into three groups depending on the elements they combine: (1) linear springs and linear dampers (LSLD), (2) linear springs and nonlinear dampers (LSND), and (3) nonlinear springs and linear dampers (NSLD). To investigate the effectiveness of the systems, a stiff piece of equipment is considered at an elevated floor within an NPP. A set of 30 triaxial ground motions is used to investigate the seismic performance of the equipment. The peak isolation displacement and peak equipment acceleration are used to assess the effectiveness of the vertical isolation systems. While all systems significantly reduce the seismic accelerations on the equipment, the relatively simple LSLD and LSND systems exhibit superior performance over multiple hazard levels.

Shaking table tests on the multi-dimensional seismic response of long-span grid structure with base-isolation

Seismic isolation technology is being applied in large long-span-structured public buildings more and more often worldwide. Aimed to investigate the horizontal and vertical dynamic response of long-span gird structure, the shaking table tests of 1/20 scale long-span grid structures with and without base-isolation considering horizontal two-dimensional (2D) and three-dimensional (3D) seismic excitations were conducted. The test model was designed as ordinary long-span spatial grid structure, but with lead rubber bearings. Data on the acceleration, displacement, strain, and shear force of the base-isolation model and fixed-base model were collected and compared. The dynamic responses of the structure subjected to the horizontal and vertical ground motions with different intensities were studied. The experimental results showed that compared with the fixed-base model, the horizontal period and damping ratio of the base-isolation model can be significantly improved, reducing the horizontal dynamic response of the superstructure, and the horizontal isolation effect was improved with the increase of the seismic excitation intensity. The horizontal acceleration of the roof layer for the base-isolation model was amplified in 3D excitation compared to horizontal input due to horizontal-vertical coupling. Meanwhile, significant vertical acceleration and displacement responses of long-span roof for fixed-base structure were induced by horizontal seismic excitation. Although base isolation could not provide protection against vertical excitation, vertical isolation effect under 3D input could be achieved by effectively suppressing the vertical dynamic response of grid roof induced by the horizontal seismic component.

Mechanical performance and shear constitutive model study of a new high-capacity polyurethane elastomeric bearing

To develop high vertical capacity bridge isolation bearing, a new polyurethane elastomer (PUE) material with improved shear performance was introduced. This paper focuses on the mechanical properties and the shear constitutive model of the PUE material and the new bearings. Four isolation bearings with different design parameters made from the PUE material were produced to evaluate the vertical bearing capacity and horizontal shear performance. Further studies on the mechanical properties of the PUE material revealed that the new material has stable yield stress and strong rate-dependent features. From the experimental results, a rheological shear constitutive model was proposed for the PUE material to describe its highly non-linear rate-dependent properties. Parameter identification tests, such as multi-step relaxation tests, cyclic shear tests, and simple relaxation tests, were conducted to identify the model parameters. Finally, the accuracy of the proposed constitutive model was verified by the isolation bearings experimental. Results indicate the PUE bearing has a large vertical bearing capacity, promising horizontal deformability and energy dissipation capacity. The proposed rheological model accurately described the highly non-linear and rate-dependent shear mechanical properties of the new PUE bearing.

Tests, model, and applications for coned-disc-spring vertical isolation bearings

To study the mechanical performance and asymmetric hysteretic models of coned-disc-spring vertical isolation (CDSVI) bearings, their mechanical properties under reversed loading conditions were tested, and the characteristics of their load–displacement hysteretic curves were investigated. The test results indicate that the load–displacement hysteretic curves have asymmetric characteristics, and that the loading frequency has only a marginal influence on the mechanical properties of the bearings, whereas the preloading displacement and dynamic loading amplitude have a critical influence. Based on the test results, an origin-oriented hysteretic model (OO hysteretic model) was proposed for CDSVI bearings. The results indicate that the OO hysteretic model has asymmetric characteristics, and the frictional forces critically influence the restoring forces of the bearings. Furthermore, the experimental results were used to verify the OO hysteretic model. The results indicate that the OO hysteretic model can simulate the mechanical performance of the CDSVI bearings effectively, and the relative errors between the simulated and experimental results of both equivalent stiffnesses and equivalent damping ratios are within 5%. Finally, the nonlinear dynamic time-history analysis of a typical CDSVI-SDOF system was carried out to study the influences of the asymmetric hysteretic model on the calculated seismic responses of the structures. Numerical results show that CDSVI bearings can effectively reduce the earthquake responses of the structure.

An active actuator based on giant magnetostrictive composite pendulum for vibration isolation

This paper proposes an active actuator based on giant magnetostrictive composite pendulum for vibration isolation, laying the foundation for vertical micro-vibration isolation. The performance of a single-stage pendulum vibration isolation system can be improved by increasing the pendulum length, along with the influence of the environment on the system increases. In precise experiments, effective isolation of vertical micro-vibration improves the accuracy of the experiments. Interference caused by micro-vibration can be attenuated by designed magnetostrictive actuators. Then, a suspension actuator consists of a composite pendulum and a driving device is designed. The composite pendulum is composed of a quartz fiber coated with a giant magnetostrictive material (GMM). The GMM can achieve the desired small strain in a designed magnetic field. GMM is applied on a quartz fiber to form a composite pendulum. Therefore, low-frequency active vibration isolation of single pendulum is realized. Compared with the passive vertical vibration isolation system, the system gets better vibration isolation and anti-interference ability. Compared with the traditional active vertical vibration isolation system, it has the advantages of system simplification, high integration and high sensitivity.

A vertical isolation device with variable stiffness for long-span spatial structures

A vertical isolation device with variable stiffness (VIVS) is developed using multiple hydraulic cylinders, which can form a three dimensional (3D) isolation device with a horizontal rubber bearing. The components and control mechanism of the VIVS are explained in detail. A prototype of the VIVS is fabricated to verify its performance by sinusoidal motion tests and shaking table tests. The experimental results show that the variable stiffness characteristics of the VIVS can be achieved, and the isolation period reaches 1.2 s. The shaking table test also verifies the effectiveness of the VIVS in controlling the acceleration. A theoretical model for the VIVS is proposed and validated, and a 60 m single-layer reticulated dome is simulated based on the model. The results indicate that the axial force and acceleration of the structures with VIVS are effectively mitigated with reduced height and displacement of the VIVS.

Displacement/velocity‐based control of a liquid spring—MR damper for vertical isolation

Seismic isolation is an effective technique used to mitigate effects of shaking and helps to achieve higher seismic performance. Recent researches have suggested that vertical excitation has significant effects on structures behavior during earthquake. In this study, three-dimensional (3D) isolation is proposed that combines an elastomeric bearing to resist horizontal ground shaking in series with a bilinear liquid spring (BLS)–controllable magnetorheological fluid damper (CMRD) to resist vertical shaking. A numerical model of a simplified rigid 2D block was developed to predict BLS-CMRD response under earthquake loading. The response of the BLS-CMRDs was simulated through a combination of nonlinear stiffness and viscous and hysteretic (semi-active) damping. A Disp/Vel-based control strategy was proposed that adjusts the input current according to the instantaneous vector combination of feedback displacement and velocity of the damper. Two variations of the control strategy were explored. First, with linear current variation, the current is activated when a threshold lower bound vector magnitude is reached, and maximum current is applied when threshold upper bound magnitude is exceeded. Second, the simplified ON–OFF strategy uses single threshold vector magnitude that triggers the maximum current to turn on when the instantaneous vector magnitude exceeds the threshold, and turn off otherwise. Results show that for ground motions that exceed the design level, Disp/Vel-based Control is effective to moderate the level of energy dissipation, keep the device vertical displacement within the design stroke limit, and attenuate vertical acceleration below PGA. In addition, Disp/Vel-based control reduces all responses relative to the well-known clipped optimal strategy used for structural control.

Temperature dependent lateral and vertical conduction mechanisms in AlGaN/GaN HEMT on thinned silicon substrate

This paper presents the influence of Si substrate thinning by grinding and dicing on the mechanical and electrical properties of AlGaN/GaN HEMT grown on 6-inch Si substrate. By experimentally removing 96% of the Si substrate, an increase in the lateral breakdown voltage by 13% is achieved for a wide temperature range. A decreasing vertical breakdown voltage with substrate thinning shows the necessity of substrate replacement to maintain the vertical isolation. Poole-Frenkel and space charge limited conduction mechanisms are identified for the vertical leakage in forward and reverse bias down to thicknesses of 200 μm, respectively. The increase in chip bow and the resulting increase in tensile strain in the epitaxial layers resulting from the substrate removal are correlated to a 40% decrease in 2DEG charge carrier concentration along with a 27% increase in threshold voltage. These findings are explained by strain-induced gate barrier and polarization charge variations.

An innovative isolation system for improving the seismic behaviour of liquid storage tanks

The current study proposes a new vertical seismic isolation of an aboveground liquid storage tank (AST) and theoretically and numerically evaluates its effectiveness for a comprehensive practical range of tank geometries. In the proposed system, 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 equations of motion for a liquid tank equipped in the proposed system were extracted using the mass-spring simplified model of contained liquid. A parametric study was performed by employing the non-linear solution of the governing equations and the effectiveness of the proposed system for all AST aspect ratios is discussed. The numerical results show that the overturning moment of the tanks equipped with the proposed isolation system decreased significantly with respect to the corresponding fully anchored tanks. The results of the parametric study on the tank aspect ratio and liquid height indicate that the proposed system is more efficient for slender tanks than for broad tanks.