Three-dimensional Isolation System Research Articles

Horizontal shaking table tests on a four-story prototype structure using multi-dimensional earthquake isolation and mitigation devices

Three-dimensional isolation system (3DIS) has been increasingly applied to civil structures with small height-width ratios, but is rarely employed in the multistory and high-rise buildings due to the lack of efficient control strategy for the rocking effect. In this paper, a simplified analysis model of 3DIS was established firstly to bring insights into the coupled motion mode caused by the rocking effect, and the influence of damping ratio and height-width ratio on the modal frequency was revealed. Then, aimed at weakening rocking motion and improving the seismic isolation efficiency, a novel multi-dimensional earthquake isolation and mitigation device (MEIMD) was proposed, and both the design composition and design principle were given in detail. To validate the effectiveness of MEIMDs, a full-scale four-story frame with a height of 13.05 m and a weight of 70 tons was produced for horizontal shaking table tests. The experimental results indicated that after adopting MEIMDs, the first-order modal frequency was 1.7 Hz, with 68% decrease compared with that of the prototype structure, and the first-order modal damping ratio was above 0.23, about eight times that of the prototype structure. Moreover, the horizontal peak acceleration was significantly decreased for each floor with a maximum reduction of 49%, while the maximum horizontal displacement and rocking response were obviously lower than the limit value specified by building codes. Therefore, the MEIMDs can not only efficiently isolate the earthquake energy, but also ensure the sufficient dynamic stability of the system. This study sheds light on the real coupled horizontal-rocking response of the base isolation system with MEIMDs, and can promote the development and application of 3DIS in multistory and high-rise buildings.

Seismic Response Analysis and Damage Calculation of Long-Span Structures with a Novel Three-Dimensional Isolation System

Seismic Response Analysis and Damage Calculation of Long-Span Structures with a Novel Three-Dimensional Isolation System

Key technologies research on of soil-structure interaction base story isolated structure response in 3D seismic zone

The development of karst in Karst area leads to poor stability of stratum. If earthquake occurs, the area will produce destructive disaster. In order to improve the stability capacity of the grassroots in the region, this study investigates the seismic response of inter-story isolation structures considering soil-structure interaction (SSI) in three-dimensional earthquakes. A model of the inter-story isolation structure incorporating SSI was developed, and one-dimensional, two-dimensional, and three-dimensional ground motions were applied to compare the seismic response under different input conditions. A three-dimensional isolation system was introduced and compared with traditional horizontal isolation structures to address excessive tensile and compressive stresses on the isolation structure during three-dimensional ground motion. The results demonstrate that the seismic response to three-dimensional earthquakes surpasses one-dimensional and two-dimensional inputs. Furthermore, adding a three-dimensional isolation structure effectively isolates vertical ground motion and reduces structural seismic response. Moreover, it minimizes soil stresses on the foundation compared to traditional horizontal isolation structure, enhancing foundation stability. This study will provide theoretical value and practical guidance for the research on key technology of SSI base story isolation structure response in Karst Plateau 3D Seismic zone.

Seismic protection of a single-layer spherical lattice shell structure using a separated three-dimensional isolation system

Vertical and three-dimensional (3D) isolation systems are emerging control technologies for spatial grid structures in high seismic intensity regions. Recently, multistage vertical isolation bearings (MVIBs) based on prepressed spring devices (PSDs) have been proposed to support the lattice shell and prevent the transfer of vertical ground motion components to the structure. Seismic dampers can be further combined with an MVIB to develop a hybrid bearing with a damping capacity. In this study, the vertical load-carrying and isolation mechanisms underlying the MVIB configuration were investigated in detail. A series of proof-of-concept tests were conducted on a prototype MVIB comprising four identical PSDs to study its actual mechanical behavior. The test results indicated that the MVIB specimen exhibited multilinear elastic behavior with enhanced load resistance. The key parameters of the tested bearing, such as the transition force and isolation stiffness, increased linearly with the number of PSDs. The MVIB model was subsequently refined using ABAQUS to comprehensively understand the mechanical performance of the spring isolator. Following a device-level study, a single-layer spherical lattice shell was used as the research target. The damped MVIBs and friction pendulum bearings were arranged at the roof supports and column bases, respectively, and the stiffness and energy dissipation properties of these isolators were designed. A system-level seismic analysis was conducted using OpenSees to compare the triaxial dynamic responses of the target structure before and after isolation. The results indicated that the separated 3D isolation system achieved its intended design goals and effectively protected the lattice shell structure from tridirectional seismic shaking.

Research and development of three-dimensional isolation system for SFR (Experimental study on static characteristics using half scale size model)

Research and development of three-dimensional isolation system for SFR (Experimental study on static characteristics using half scale size model)

Experiment investigation and dynamic responses of three-dimensional isolation system with high-static-low-dynamic stiffness

The application of three-dimensional (3D) isolators was limited due to the demands of long isolation period and strong supporting capacity. This paper introduces the configuration and mechanical behavior of 3D isolation system with high-static-low-dynamic stiffness (HSLDS). The proposed 3D isolator consists of the negative stiffness device and pre-deformed inclined rubber bearing. The mechanical model combining negative and positive stiffness is developed. Furthermore, experiments on both the separated and combined negative stiffness device and the pre-deformed rubber bearing are performed to characterize the behavior of HSLDS isolator. Subsequently, a numerical study of different isolated structures is performed and the variations on the structural responses as well as the hysteretic loops are illustrated. By comparing the vertical accelerations and the isolator behavior, the efficiency of HSLDS isolator on mitigating the structural acceleration as well as the vertical static displacement is confirmed.

Research and Development of Three-Dimensional Isolation System

The design basis ground motions have been revised to improve the seismic resistance of nuclear power plants. The reduction of seismic forces not only horizontally but also vertically has required more critical than in the past to ensure the seismic resistance of components. Notably, the design of a Sodium-Cooled Fast Reactor will require reducing the seismic forces applied to the components because of the components with thin wall thickness. To overcome this problem, the authors have been developed an innovative three-dimensional seismic isolation system. This seismic isolation system will be applied to the reactor building, as the isolated reactor building. Investigating the force and displacement relationships of this seismic isolation system is an essential process to verify the feasibility of the design for the isolation system. The static loading tests were conducted to verify the force and displacement relationships in horizontal and vertical directions, which used a half scale three-dimensional isolation system. This paper demonstrates that the horizontal supporting function enables a stable load path and the independence of the force and displacement relationships in horizontal and vertical directions to ensure even under simultaneous horizontal and vertical loading assumed in the design basis ground motion.

Research and Development of Three-Dimensional Isolation System for SFR

The development of a SFR(:Sodium-cooled Fast Reactor) is carried out by Japan Atomic Energy Agency and others. Not only the decrease of horizontal seismic loads, but also the decrease of vertical seismic loads is important in SFR which has thin wall structures. Accordingly, the three-dimensional isolation system is developed for the seismic design of the components. This isolation device consists of a thick rubber bearing, four coned disc spring units, four vertical oil dampers, eight sliding functions and a supporting function. Furthermore, horizontal oil dampers are installed for damping force. This isolation device has few critical development elements and no additional function such as the rocking suppression device. In this isolation system, the natural frequency in the horizontal direction is 0.29Hz, the natural frequency in the vertical direction is 3.0 Hz. This isolation device is premeditatedly developed from 2017. This project has carried out load tests with full and half scale coned disc springs. The design method of coned disc spring units has been confirmed. Furthermore, this project has developed the horizontal oil damper of high allowable velocity and the vertical oil damper. This project is carrying out load tests of the half scale three-dimensional seismic isolation device, which consist of the thick rubber bearing, the coned disc spring units, the supporting function and so on. The development of this isolation device will be continued sequentially. The fundamental design method of this isolation device is confirmed in this project.

Dynamic Analysis of a Spring-Asphalt Three-Dimensional Isolation System Based on Cyclic Simple Shear and Shaking Table Tests

Damping is one of the important issues related to isolated structures, including the newly proposed low-cost spring-asphalt isolation system. In this study, the damping properties of the system in terms of displacement dependence, frequency dependence and temperature dependence were studied by a cyclic simple shear experiment. Then, the direct least-square method was used to identify the damping properties from the experimental data. Furthermore, to validate the effectiveness of the damping device, a modal analysis was conducted based on multi-dimensional shaking table tests. The results indicate that (1) the hysteretic curves are similar to an ellipse, which means that the asphalt shows characteristics of viscoelastic materials; (2) the damping properties are positively related to the loading frequency and inversely related to the temperature and displacement; and (3) asphalt can provide adequate damping and reduce the displacements of the superstructure by nearly half. On the basis of the experimental test results, an analysis of the modal information with multi-dimensional input is also presented.

Numerical Simulation of a New 3D Isolation System Designed for a Facility with Large Aspect Ratio

This paper proposes a novel three-dimensional (3D) isolation system for facilities and presents the numerical simulation approach for the isolated system under earthquake excitations and impact effect using the OpenSees (Open... | Find, read and cite all the research you need on Tech Science Press

Probabilistic seismic assessment of seismically isolated electrical transformers considering vertical isolation and vertical ground motion

This study presents a probabilistic response analysis of seismically isolated electrical transformers with emphasis on comparing the performance of equipment that are non-isolated to equipment that are isolated only in the horizontal direction or are isolated by a three-dimensional isolation system. The performance is assessed by calculating the probability of failure as function of the seismic intensity with due consideration of: (a) horizontal and vertical ground seismic motions, (b) displacement capacity of the seismic isolation system, (c) limit states of electrical bushings, (d) details of construction of the isolation system, (e) weight of the isolated transformer, and (f) bushing geometry and configuration. Calculations of the probability of failure within the lifetime of isolated and non-isolated transformers at selected locations are also performed. The results of this study demonstrate that seismic isolation systems can improve the seismic performance for a wide range of parameters and that systems which isolate in both the horizontal and vertical directions can be further effective. The seismic assessment methodology presented can be used for: (a) deciding on the need to use seismic isolation and selecting the properties of the isolation system for transformers depending on the design limits, location, and configuration of transformer and (b) calculating the mean annual frequency of functional failure and the corresponding probability of failure over the lifetime of the equipment. The results may also be used to assess the seismic performance of electric transmission networks under scenarios of component failures.