Seismic Isolation Devices Research Articles

Feasibility Evaluation of Novel High-Damping Rubbers as Energy-Dissipation Material under Axial Dynamic Load for Damper Devices

High-damping rubber (HDR) material has been widely used in bearings for seismic-isolation devices in structures. Nevertheless, HDR has not yet been developed in dampers to reduce the response of structures to earthquake excitations by dissipating the energy applied to the structures under direct axial load. The purpose of this paper was to evaluate the feasibility of using novel hyperelastic composite material (HECM), which is an HDR material, in experimental investigations to determine its damping ratio, compressibility, and elasticity behavior under axial dynamic load for the development of novel dampers in the future. First, a series of tests on HECM was conducted using the double-shear method to determine the most suitable sample for a purely dynamic compression test. Subsequently, the HECM was used in a device working as a scaled-down damper under both direct tension and compression dynamic load conditions, and pure direct compression dynamic load conditions were tested. Various thicknesses of the HECM (6, 8, and 10 mm) used in the testing damper were examined under a constant force with various frequencies of 0.01, 0.1, 0.25, and 0.5 Hz. The results show that the 10 mm thick HECM can provide a high damping ratio of 10% to 13% under axial conditions. Hence, this study is important for evaluating HECM, which has the potential for use in developing a full-scaled rubber damper system to resist axial force in the future. The damper is a novel rubber damper with high damping capability to dissipate energy under axial load. Furthermore, the damper can serve as an alternative choice that is more durable and overcomes the current weaknesses of passive dampers.

Vertical distribution of seismic design load for seismically isolated buildings corresponding to diversity of seismic isolation devices

AbstractThis paper proposes a vertical distribution of seismic design load of seismically isolated buildings corresponding to diversity of seismic isolation devices such as hysteretic dampers and/or velocity‐dependent dampers. This proposed method is obtained from the relationship between response amplification caused by higher‐mode responses and key parameters such as Isolation ratio and Non‐linearity factor which evaluate structural characteristics of seismically isolated buildings. This response amplification is explained by nonlinear modal analysis with free‐free vibration mode. In addition, it is confirmed that this proposed method adapts to various model of seismically isolated buildings.

Reformulation of a phenomenological model for symmetric rate-independent hysteresis

The present paper enhances, both theoretically and numerically, a recent uniaxial phenomenological model aiming to reproduce complex hysteretic behaviors of seismic isolation devices, including steel- and fiber-reinforced elastomeric bearings, presenting smooth hysteresis loops with hardening and/or softening regions. The investigated constitutive model is based on five parameters that can be directly related to the experimentally observed hysteresis loops. Moreover, because of its analytical nature, the presented formulation is capable of computing in closed form the generalized response relevant to any displacement increment starting from a known equilibrium state. Hence, differently from the original differential formulation of the investigated model as well as from popular materials such as the celebrated Bouc–Wen, the presented formulation does not require any iterative strategy for computing the hysteretic force. Finally, the investigated model is validated by numerical simulations compared with experimental tests selected from the literature.

Selection of seismic isolation system parameters for the near-optimal design of structures

The benefits of seismic isolation are many. Structures that are isolated from the ground seismically perform better than those that are not. They experience reduced floor accelerations and drifts and are less likely to experience damage to structural elements. Additionally, their contents are better protected from the effects of earthquakes. The selection and design of seismic isolation devices are complex and require a good understanding of how they behave during earthquakes. This study investigates the effect of various isolation system parameters and ground motion characteristics on the seismic response of base isolated structures in order to develop rational procedures for design and analysis. Additionally, the study investigates the problem of optimal design of seismic isolation systems through parametric nonlinear dynamic analysis. Results showed that the maximum base shear and displacement were velocity-sensitive and that the peak ground velocity controls the motion. The largest maximum base shear occurred when using isolation systems with high yield strength levels and low degrees of nonlinearity, while the smallest maximum base shear occurred when using low yield strength levels and high degrees of nonlinearity. Results from the study can be used to select the appropriate isolation devices and design them correctly to achieve the benefits they provide.

Effectiveness of Different Base Isolation on Stepped Buildings

Abstract: Seismic isolation devices are commonly employed to protect structures from the impacts of severe ground motions. ETABS2016, a modelling and analysis programme, was used in this work to model and analyse the isolated stepped building. Rubber isolator link components were used as a single joint element to represent the rubber isolators between the ground and the superstructure. El-Centro seismic records were used to analyse the isolated building. The lateral inter-storey drifts, story displacement and peak absolute floor accelerations, of the isolated building were compared to those of the fixed-base structure. The current study aims to evaluate the effectiveness of several types of base isolation systems for seismic protection of 6-story stepped structures using Time history analysis. The isolation systems considered include, i) rubber isolators, ii) rubber isolators with energy dissipation systems, and iii) friction pendulum isolators.

Lead-rubber-bearing with negative stiffness springs (LRB-NS) for base-isolation seismic design of resilient bridges: A theoretical feasibility study

Advanced seismic isolation devices and systems have been recognized as promising measures toward resilient design of bridge structures. This paper proposes a base isolation system using lead rubber bearing with negative stiffness springs (LRB-NS), which is composed of traditional lead rubber bearing (LRB) and pre-compressed springs, installed at the bottom of bridge columns. These springs contain dual functionalities: (1) provide negative stiffness (NS) and negative restoring force during slight shakings and elongate the structural period that is determined by LRB products; and (2) offer significant restoring forces to prohibit excessive peak deformation and protect bearings from failure when subjected to strong earthquakes. Theoretical and analytical studies are first conducted to illustrate fundamental mechanics of the proposed LRB-NS device, followed by a series of parametric analyses to understand the influential factors of this device on structural behavior. Moreover, fragility analyses of typical highway bridges are conducted to demonstrate the feasibility of LRB-NS device via comparisons with non-isolated and traditional LRB systems. The results show that the LRB-NS device can be well designed to mitigate seismic demands of bridge columns, as well as highly effective to suppress the excessive deformation in bearings that often occurs in the traditional LRB system under strong excitations. The LRB-NS device can be used to facilitate the resilient seismic design of bridge structures.

Seismic isolation technology for prestressed segmental precast piers

Prestressed segmental precast (PC) piers, with insufficient energy dissipation capacity, are seldomly adopted on bridges in seismic areas. To improve the seismic performance of PC piers, this study proposes a functional separation seismic isolation device (FSID), serving as a supplementary replaceable energy dissipation device. Full-scale field load tests on a real-world PC pier were carried out to qualify the seismic performance of this type of piers. Based on the results of tests and supplementary numerical analysis, an optimal design of the FSID was achieved. The numerical results show that the FSID has multi-stage statuses and reaction models. By optimizing the design parameters, FSID can enable the PC piers to satisfy the required seismic performance under various levels of earthquakes. Therefore, the performance-based seismic design of PC piers can be achieved using the FSID.

Mechanical properties and seismic isolation behavior of scrap tire pads subjected to thermal-cold cycles in rural construction

This paper presented systemic research evaluating the mechanical properties and seismic isolation behavior of scrap tire pads (STP) subjected to thermal-cold (TC) cycles. The mechanism of the TC-damaged tire rubber was linked to the mechanical characteristics and seismic isolation behavior of the TC-damaged STP. Thus, the deterioration mechanism of the TC-damaged tire rubber was investigated first. Then, vertical compression tests were conducted with 15 groups of STP to study the vertical mechanical properties. The vertical stiffness, vertical deformation performance, and vertical ultimate bearing capacity were analyzed. Results showed that with an increasing number of TC cycles, the vertical deformation performance and vertical ultimate bearing capacity of STP decreased, whereas the vertical stiffness increased. In addition, to promote the use of STP in village frame structures, a novel seismic isolation device under the column (SIDC) was proposed. In SIDC, the hysteresis behavior, destructive properties, horizontal equivalent stiffness, and equivalent damping coefficient of STP were investigated. The results showed that the horizontal equivalent stiffness was lowered by 45.20 %, the equivalent damping coefficient dropped by 8.04 %, and the cumulative energy degradation was up to 35.0 % when the number of TC cycles increased to 520 compared to that of STP without TC cycles. Finally, an optimized nonlinear two-spring restoring force model was proposed to describe the hysteresis hardening characteristics of TC-damaged STP in SIDC. Furthermore, the theoretical model and experimental findings were compared, with the theoretical model describing the hysteresis hardening behavior the best.

Seismic Analysis of Reticulated Shell Structure Based on Sensor Network for Smart Transportation Seismic Isolation Bearings

Earthquakes are one of the most frequent and inevitable natural disasters that occur on Earth. The most important seismic isolation device used in the isolation technology is the isolation bearing, but the limited structure of the isolation bearing is not suitable for the seismic isolation and shock absorption of smart transportation buildings. Therefore, it is very important to improve the new generation of seismic isolation structures with good seismic isolation effect, stable performance, and economical performance. It is very important to study the structural composition of the isolation bearing and the rigidity of the isolation structure. Isolation bearings are designed to resist and absorb the energy of seismic shocks by installing substructures in the structure. Active control involves installing sensors on the structure and its foundation to determine how the structure responds to seismic action. In this paper, based on the intelligent transportation of the sensor network, the reticulated shell structure of the isolation bearing is analyzed. By introducing the architecture and network layout of the sensor network, it is beneficial to obtain more accurate seismic data in complex and difficult terrain. This paper analyzes the technical principle of seismic isolation technology, which can effectively avoid the upward transmission of ground vibration by increasing the flexibility and proper damping of the system. From the experimental data of the seismic response of the ground-isolated structure to the near-field pulsation and far-field vibration, the total energy of the ground-isolated structure under the near-field pulsed ground motion is the largest. The seismic isolation effect of the reticulated shell structure of the seismic isolation bearing prevents more than 80% of the seismic energy from being transmitted to the superstructure.

Design, manufacturing, and performance evaluation of a novel smart roller bearing equipped with shape memory alloy wires

In this study, a new type of seismic isolation device, called shape memory alloy (SMA) wire-based roller bearing (SMA-RB) is developed and introduced. The SMA-RB has been designed, manufactured, and experimentally tested. This bearing consists of cylindrical roller bearings and SMA wires with straight or cross configurations, as supplementary damping elements. In such a smart bearing, the superelastic (SE) SMA wires are passed through the hooks/pulleys attached to the supporting plates of the bearings in different configurations. The rollers provide lateral flexibility, and SMA wires supply energy dissipation and self-centering (SC) properties. In the manufacturing stage, a new mechanism for coupling wires (i.e. SMA wire joiner/coupler) is proposed. The results show that SMA wires, made of nickle titanium (NiTi), provide a SC damping mechanism with almost zero residual deformation which can effectively control the device from over-displacement. While using pulleys and newly designed wire joiners in the SMA-RB, the bearing can experience a stable cyclic behavior. Since the rollers generate a negligible amount of frictional force, the SE NiTi wires with a flag-shaped hysteresis mainly contribute to the overall shear hysteretic response of the SMA-RB. A triangular-shaped constitutive model can be used to accurately describe the hysteretic behavior of SMA-RB with different wire configurations.

Polishing Performance of a Recycled Grinding Wheel Using Grinding Wheel Scraps for the Wet Polishing of Stainless-Steel Sheets

The surfaces of large austenitic stainless-steel sheets, which have side lengths of at least 1 m a sheet thickness of at least 6 mm, used for food tanks and sliding plates in seismic isolation devices, must be finished to a mirror surface. Polishing is performed to improve the surface quality of such sheets and dry machining is typically applied. The problems associated with dry machining are the exhaust heat of machining and treatment of chips. A transition to wet machining is required to solve these problems. In our laboratory, we have developed a wet polishing machine and researched the selection of grinding wheels to develop wet polishing technology for large stainless-steel sheets. In this study, to reduce tool cost and reuse resources, we attempted to manufacture a recycled grinding wheel using snippets of grinding wheel scraps. A polyvinyl alcohol (PVA) aqueous solution was used as the bonding agent for the recycled grinding wheel to reduce environmental load. To overcome the ease of dissolution of PVA in water, we attempted to improve the water resistance of the PVA aqueous solution by incorporating an organic titanium compound. This is one of our efforts to contribute to sustainable development goals. The results are summarized below. (1) A recycled grinding wheel was fabricated by kneading crushed pieces of grinding wheel scrap with a bonding agent. (2) The maintenance of the shape of the recycled grinding wheel was controlled by the concentration of the bonding agent. (3) The recycled grinding wheel with a PVA bonding agent was vulnerable to water. In contrast, the recycled grinding wheel to which the organic titanium compound was added exhibited improved water resistance. (4) The polishing of stainless-steel sheets using the plain PVA recycled wheel was relatively ineffective, but polishing using the recycled wheel with the titanium additive was comparable to polishing with a new grinding wheel.

Performance Verification of Vertical Seismic Isolation Equipment Using Negative Rigidity Mechanism

In recent years, various seismic isolation devices have been developed to prevent earthquake damage to valuable art works. The purpose of this study is to develop a vertical seismic isolation system that both reduces the natural frequency and solves the problems of vertical seismic isolation systems in previous studies. In this study, we developed a vertical seismic isolator that supports the load with inclined springs without using vertical springs. A motor is mounted on the ball screw that constitutes the central axis of each crank mechanism. The vertical stiffness of this seismic isolator can be changed using the motor. In this study, the seismic isolation performance was improved by using the negative stiffness property to set the natural frequency lower. The vertical seismic isolation system was modeled using SimulationX. The characteristics of the vertical seismic isolation system were verified and its performance was evaluated by various experiments and simulations. The MBS model of the newly developed device was used to accurately simulate the loading characteristics of the vertical isolator such as negative stiffness characteristics. The performance of this vertical isolator was verified by vibration experiments and simulations assuming typical seismic waves in Japan. The average response factor of acceleration in the experiment was 17.8%, and the average response factor in the simulation was 15.9%, which exceeded the performance of the device in the previous study. Finally, in the resonance avoidance test, the acceleration of the top plate of the vertical base isolation system was reduced by 57% by using the vertical natural frequency adjustment mechanism to avoid resonance.

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.

Analytical prediction of mechanical properties in horizontal direction of lead-rubber bearings

Application of seismic isolation devices is an efficient way for designing seismically resistant structures. For that purpose, various types of seismic isolation devices are developed. The main differences between them are in the materials used for their production and in the way they provide horizontal flexibility. Dynamic analysis of a base isolated structure requires an adequate mathematical model of the seismic isolation devices which can describe their mechanical properties in horizontal and vertical directions. The paper is considering analytical models used for the prediction of mechanical properties in the horizontal direction of lead-rubber bearings, which are proposed in the contemporary literature. Results obtained using these analytical formulas are compared with the results obtained by the finite element analysis model developed in this paper, as well as with available test results provided by the manufacturer. Improvements of the existing analytical models are suggested in order to enable a better prediction of mechanical characteristics in the horizontal direction of lead-rubber bearings.

Vertical Seismic Isolation Device for Three-Dimensional Seismic Isolation of Nuclear Power Plant Equipment—Case Study

The purpose of this study was to develop a vertical seismic isolation device essential for the three-dimensional seismic isolation design of nuclear power plant equipment. The vertical seismic isolation device in this study has a concept that can be integrally combined with a conventional laminated rubber bearing, a horizontal seismic isolator with a design vertical load of 10 kN. To develop the vertical seismic isolation device, the vertical spring and the seismic energy dissipation device capable of limiting the vertical displacement of the spring were designed and their performances were verified through actual tests. In this study, the target elevation of the floor is 136 ft, where safety-related nuclear equipment, such as cabinet and remote shutdown console, etc., is installed. The sensitivity studies were carried out to investigate the optimal design vertical isolation frequencies for the target building elevation. Based on the results of the sensitivity study, a disc spring and a helical coil spring were selected for the vertical stiffness design, and the steel damper was selected for the seismic energy dissipation, and their performance characteristics were tested to confirm the design performance. For the steel damper, three types were designed and their energy dissipation characteristics by hysteretic behavior were confirmed by the inelastic finite element analyses and the tests in static fully reversed cyclic conditions. Through the study of the vertical seismic isolation device, it was found that 2.5 Hz~3.0 Hz is appropriate for the optimal design vertical isolation. With results of the vertical seismic isolation performance analysis, the appropriate number of steel dampers are proposed to limit the vertical seismic displacement of the spring within the static displacement range by the design vertical load.

Probabilistic methods for calculating seismic resistance of buildings

The article aims to assess possibilities of using probabilistic methods for calculating seismic resistan of buildings based on the laws of structural mechanics. The design schemes and models of buildings rigidly embedded in the base and with a seismic isolation device are described. Formulas developed on the basis of the law of energy conservation, namely the seismodynamic law, which allow to estimate the coefficient of dynamism, are presented. It is proposed to abandon the main modes of vibration in the calculations, i.e. the coefficient ηir of the waveform and the vibration frequency of the residential building and the foundation during earthquakes. Shear and bending calculations of a residential building are based on the design model developed. The values of seismic force are determined by the first and last modes of vibration. Based on these values, it is proposed to calculate internal forces and deformations in the bearing structures of buildings using the methods of structural mechanics.

Experimental and numerical investigation on a passive control system for the mitigation of vibrations on SDOF and MDOF Structures: mini Tribological ROCKing Seismic Isolation Device (miniTROCKSISD)

ABSTRACT This paper illustrates the results of an experimental campaign performed on a scale prototype of a base dissipator called Mini Tribological ROCKing Seismic Isolation Device. This device allows a smooth, controlled and damped rocking by means of frictional layers and viscous elastic springs, which aim at decoupling the frequencies of the superstructure, at dissipating energy during motion and at re-centering the system once the external action vanishes. Four superstructures are tested – a shear type frame, braced and unbraced, a multi-story frame and a SDOF oscillator – with 96 ambient vibration and impulsive tests. An analytical model is illustrated and validated by the experimental tests. The reduction of relative displacement demand is analyzed for all the cases together with the reduction of the acceleration demand, showing positive effects of the base dissipator on the dynamic behavior of all the superstructures.

Retraction: Design of Base Isolation System for a Six Storey Reinforced Concrete Building (IOP Conf. Ser.: Earth Environ. Sci. 796 012034)

This article has been retracted by IOP Publishing following a request by the authors that this article may contain potential research errors. IOP Publishing has investigated in line with COPE guidelines, and during the course of the investigation were made aware the article contains potential similarities to other published works [1-4]. Due to the nature of the overlap identified, and the extent of the changes requested by the authors, the journal has lost confidence in the validity of the findings presented and agree this article should be retracted. The authors have neither confirmed whether they agree or disagree to this retraction. [1] A Hassan and S Pal, 2017, Performance Analysis of Base Isolation and Fixed Base Buildings, International Conferences on Emerging Technology in Structural Engineering (ETSE-2017) [2] Business Bliss Consultants FZE. (November 2018). Base Isolation Devices for Seismic Isolation. Retrieved from https://ukdiss.com/examples/base-isolation-devices-for-seismic-isolation.php?vref=1 [3] Ta-Chieh Wu, 2001, Design of Base Isolation System for Buildings, thesis, Massachuetts Institute of Technology [4] Y Mehani, A Benyoucef and B Chikh, 2015, Seismic Assessment demand of Isolated buildings, 7th International Conference on Seismology and Earthquake Engineering Retraction published: 21 November 2022

Multibody Modeling Method for UHV Porcelain Arresters Equipped with Lead Alloy Isolation Device

This paper presents a multibody modeling method for seismic analysis of UHV porcelain surge arresters equipped with a kind of seismic isolation device. An UHV arrester is modeled as a planar multibody system whose number of DOF is equal to the number of the arrester units. Joint coordinate method is adopted to construct the governing equations of motion. The seismic isolation device utilizing a number of lead alloy dampers as its core energy dissipation components is also investigated. An analytical model of this device is given by modeling each lead alloy damper as a hysteretic spring and reducing the entire device to a planar system consisting of a range of hysteretic springs. Its mechanical characteristic is derived theoretically, and the obtained moment-angle relationship is expressed as a system of differential algebraic equations. The initial rotational stiffness of the device is formulated in terms of the structural and mechanical parameters of the device. This analytic expression is used in estimating the fundamental frequency of the isolated equipment. By this modeling method, it is easy to construct the governing equations of motion for the isolated system. An UHV arrester specimen is analyzed by this proposed method. The effectiveness of the isolation device in terms of reducing the internal base moment is significant and the influence of system parameters on the effectiveness is also discussed. The proposed method shows its potential usefulness in optimal design of the isolation device.

Seismic fragility analysis for tall pier bridges with rocking foundations

Costal bridge systems usually contain tall piers with heights over 40 m, due to the engineering site exposed to deep water circumstances. Note that the conventional seismic isolation devices (e.g., isolation bearings) are not that effective for tall piers, since their dynamic performance is significantly affected by the distributed mass and vibration modes of columns; therefore, base isolation design philosophy could be a promising alternative for mitigating seismic demands of this type of bridges. This paper mainly investigates the efficiency of rocking foundations in improving seismic performance of tall pier bridges, with the results presented in the format of fragility curves. Finite element model of the prototype tall pier bridge is developed, and the responses subjected to near-fault motions are obtained using nonlinear time history analysis. Probability seismic demand models and fragility curves are then developed accordingly, based on which the performance of tall pier bridges are assessed. The results show that employment of rocking foundations could significantly reduce the demands of tall piers and the probability of being damaged. Before the initiation of uplifting at pier base, the behavior of rocking piers resembles that of conventional ones with integrated foundation. While rocking initiates under strong excitations, the demands of rocking piers reduce drastically compared with integrated ones and tend to be similar under different motions, which benefits the post-earthquake performance assessment of these bridges.