Isolation System Research Articles

Shake table testing of a seismic isolation system for lightweight structures

AbstractThe implementation of seismic isolation in lightweight structures, such as houses, is limited, except for Japan, where nearly 5000 houses are seismically isolated with highly engineered systems. The use of such systems in countries of growing economies is prohibitive due to their cost, difficulties in locally fabricating components, and incompatibility with local construction practices. Previous studies on low‐cost isolation systems showed that isolation devices with rolling rather than sliding elements are more suitable for lightweight structures. A low‐cost isolation system based on a deformable rolling bearing developed at the University at Buffalo has simple components that can be easily manufactured, has a large displacement capacity, and features a fail‐safe mechanism. The bearing is composed of one flat and one concave concrete plate and a rubber rolling ball. This paper presents the results of shake table testing of half‐length scale versions of prototype houses and small bridges equipped with this deformable rolling isolation system in three‐directional seismic excitation. The results showed that deformable rolling bearings provide significant seismic protection of lightweight structures against strong ground motions, which in the testing reached a maximum peak ground velocity of 1.2 m/s in the test scale and a peak ground acceleration of 4 g in the horizontal direction and up to 1 g in the vertical direction. The isolation system was particularly effective in the horizontal direction, whereas it did not provide any vertical isolation. The tests included cases of extreme response, which included vertical impact within the bearing's components and uplift of the isolated structure.

Operation status monitoring for 500 kV DC circuit breaker with internal failures and relative backup fault isolation schemes

As the primary protection and control device in direct current (DC) power systems, DC circuit breakers (DCBs) have complex structures and numerous components, making it prone to diversified internal failures. This paper explores an operation status monitoring method for DCBs, and relative backup fault isolation schemes and system recovery schemes are proposed to handle cases of DCBs with different internal failures. Contributions of this paper are: (1) An operation status monitoring method is proposed to reflect the failure degrees of DCB, categorizing the statuses of DCB into status-1 (normal), status-2 (minor failure) and status-3 (major failure). (2) According to the failure degrees of DCB, relative backup fault isolation and system recovery schemes are proposed to ensure the fault isolation scope is as small as possible and the system could recovery as fast as possible. Simulations are conducted in PSCAD/EMTDC for validation.

Investigating the Performance of Data-Driven Ensemble Machine Learning Models in Preliminary Designing Multi-Stage Friction Pendulum Bearings

Over the last few decades, the field of base isolation systems has demonstrated enormous advancements through the innovation of novel systems, and there has been an enhancement in the performance of structures equipped with isolation under conditions of moderate and severe seismic activity. One of the most important systems is the multi-stage friction pendulum, which offers a spectrum of effective pendulums across different regimes, thereby achieving enhanced capability for energy dissipation. The difficulty in designing these bearings at the preliminary stage comes from the fairly long process of trials and errors in selecting the properties of each sliding surface so that the required effective period, effective damping, and displacement capacities are achieved. This study investigates the performance of various data-driven ensemble machine learning models in directly designing multi-stage friction pendulum bearings. Within the context of the analysis, the most recent generation of friction pendulum that has been introduced to the literature, the quintuple friction pendulum, is used as the investigation employs a case to assess the dependability of the design strategy and the efficacy of a multi-output machine learning techniques. In general, the findings of this study have shown that machine learning models provide an accurate way to directly design quintuple friction pendulum isolators and attain the necessary properties of the isolators. The practicality of this research lies in highlighting how machine learning can be applied to considerably expedite the design and optimization of multi-stage friction pendulum bearings and in defining the most suitable machine learning technique to adopt in such tasks.

Application of one-dimensional periodic layers with elastomeric seismic isolators for three-dimensional isolation

Three-dimensional (3D) seismic isolation is an appealing idea to protect structures and their components from earthquake-induced horizontal and vertical ground motions. Past attempts to develop 3D isolation systems were ineffective due to their complexity and reliability issues. One-dimensional periodic material-based isolation systems (1D-PIS) have been extensively researched for applications as raft foundations due to their simple and construction-friendly unit cell designs. These systems aim to attenuate seismic excitations in both horizontal and vertical directions. However, the effectiveness of 1D-PIS in mitigating 3D excitations may be limited due to the potential mismatch between the frequency content of horizontal and vertical vibrations. The present study proposes to combine a conventional horizontal isolation system with a 1D-PIS in the vertical direction to achieve a simple, passive, and efficient three-dimensional isolation system for structures and components. The 1D-PIS is strengthened by incorporating steel shims within the rubber layers and implementing steel casings at its periphery, enabling its utilization as an isolated system. Small-scale experimental and numerical investigations were conducted on strengthened 1D-PIS to study its isolation characteristics in the vertical directions. The study reveals that infinite boundary conditions required for the efficacy of 1D-PIS were achieved through lateral restraint provided by steel shims and steel casings. Notably, the individual isolation characteristics of the conventional and the 1D-PIS are not compromised in the combined isolation system. Nonlinear time history analysis on a prototype combined isolation system confirms its effectiveness in attenuating the seismic response under simultaneous horizontal and vertical ground motions.

Active micro-vibration isolation system for adaptive vibration suppression tests using piezoelectric stack actuator

An active micro-vibration isolation system for adaptive vibration suppression using piezoelectric stack actuators is presented, along with the discrete time modelling method, real-time adaptive controller design, and hardware implementation. The system comprises piezoelectric stack actuators, capacitive displacement sensors, power amplifiers, signal conditioners, and a real-time computer. A discrete asymmetric Bouc-Wen model is developed to characterize the nonlinear behavior of the piezoelectric stack actuators. System identification is conducted using an improved particle swarm optimization method, specifically the Hybrid PSO-Jaya algorithm, which sequentially integrates the PSO algorithm with the Jaya algorithm. Additionally, an improved adaptive filtering algorithm employing affine projection, referred to as the FXAPA algorithm, is introduced to facilitate real-time control. The efficacy of the proposed active micro-vibration isolation technology is validated through micro-vibration suppression tests.

SH‐waves in a complex fluid composite structure with spring membrane imperfect interfaces

AbstractComplex fluids are of nobleness due to their unique mechanical responses to applied stress, which are different from simple fluids. Therefore, the current study encapsulated the behavior of SH‐wave in a complex fluid layer overlying a fiber‐reinforced half‐space with six different cases considered at the common interface. These cases involve various interface conditions, including perfect bonding, a spring layer, an infinitely thin membrane layer, loose bonding, a combined spring‐membrane layer, and a membrane layer with loose bonding. Precisely, the effect of loose bonding, membrane strength, and spring stiffness at the common interface on the propagation of SH (Shear Horizontal) wave is studied in detail. The problem is mathematically formulated for all the aforementioned six models followed by their solution with the aid of appropriate boundary conditions. Numerical computations are performed with a view to study the effect of stiffness of spring and membrane, as well as loose bonding at the common interface of the media. It is demonstrated that membrane strength impedes wave propagation, while increased spring stiffness supports it. Notably, the combined spring‐membrane interface has a more pronounced effect than a spring layer alone. The findings of this study may be utilized in the development of membrane technology, including the study of fluid membranes and it has significant importance in seismic engineering and vibration isolation systems.

Ultra-low frequency active vibration isolation system with quasi-zero stiffness characteristic using self-tuning filter-based feedforward control

Ultra-low frequency active vibration isolation system with quasi-zero stiffness characteristic using self-tuning filter-based feedforward control

Theoretical characteristics of a three-point Roberts linkage.

The Roberts linkage is recognized for enabling long-period pendulum motion in a compact format. Utilizing this characteristic, we are developing a three-point Roberts linkage for vibration isolation systems, with an eye toward its potential contribution to the development of next-generation interferometric gravitational wave antennas. In this article, we derived the equations to determine the essential parameters when using this linkage as a vibration isolation system, namely, the equivalent pendulum length and the relationship between translational motion of the center of mass and rigid body rotation, from size parameters. In addition, we analyzed the behavior in response to various errors.

Design and shock isolation performances of two-layered ring-spring meta-isolation systems

Two-layered ring-spring-resonator (RSR) based meta-isolation system (RSR-M) has been developed to improve shock isolation effect. In the numerical calculations, shock acceleration ratio (SAR), shock displacement ratio (SDR) and relative displacement ratio (RDR) were introduced to evaluate the shock isolation performances of the conventional isolation system (CON) and the RSR-M, considering the effects of the excitation amplitude, the weight of the middle mass block and the stiffness of the lower isolators. The results demonstrate that the SAR of the RSR-M is always smaller than that of the CON, and the SDR of the RSR-M is first larger than that of CON in the shock amplification region and then smaller in the isolation region. The weight of middle mass blocks has little influence on the isolation performance of the RSR-M because of the softening behavior of the isolators. Finally, shock isolation experiments were also carried out to measure the damping ratios of the selected wire rope isolators and further analyze the isolation performance of the RSR-Ms. In general, meta-isolation system provides a new reference and idea for the design of the isolation system of engineering structures in some sense.

Full Road Transport Sector Transition Towards 100% Autonomous Renewable Energy Supply in Isolated Systems: Tenerife Island Test Case

Full Road Transport Sector Transition Towards 100% Autonomous Renewable Energy Supply in Isolated Systems: Tenerife Island Test Case

Seismic isolation strategy via controlled soft first story with innovative multi-stage yielding damper: Experimental and numerical insights

While the presence of a soft story within a building is typically discouraged in structural engineering due to potential vulnerabilities, this research proposes a strategy that incorporates seismic isolation concepts by integrating a soft first story within the structural framework. This approach challenges traditional reluctance by demonstrating the potential benefits of such a configuration. The primary objectives are twofold: firstly, to diminish seismic responses and enhance structural resilience when subjected to earthquake forces, and secondly, to reduce construction costs as compared to conventional passive control methods. The seismic responses assessed and compared in this study encompass story displacements, story drifts, floor accelerations and base shear of the structure. Furthermore, an investigation is conducted into a replaceable or repairable shear fuse that serves as a controller in the Controlled Soft First Story (CSFS) strategy, namely, an innovative Multi-stage Steel Yielding Damper (MSYD). Notably, the numerical analysis of the introduced damper has been carried out, followed by rigorous validation testing under experimental conditions. This study elucidates the implementation of this strategy within the structural framework. The overarching principle behind employing the CSFS results in outcomes akin to those achieved with base isolation techniques. However, it distinguishes itself by significantly mitigating the construction costs around 70% associated with this system when juxtaposed with traditional base isolation systems.

Experimental study on seismically isolated systems using a novel roller-type bearing with energy dissipation capacity

The roller-type isolation bearing is highly effective in limiting the transmission of lateral seismic forces to the superstructure. This paper introduces a novel roller-type bearing with energy dissipation capacity (RB-EDC), which includes flat bearing seats, rollers, limit plates with energy dissipation capability, and limit rings. The RB-EDC is characterized by its excellent energy dissipation capacity, simple manufacturing process, low cost, vertical tensile bearing capacity and stable performance in extremely cold regions due to its specific configuration and materials. The design procedure for the RB-EDC is detailed herein. Subsequently, pseudo-dynamic comparison tests were conducted on both a seismic isolation system specimen and a RC column specimen under frequent and rare earthquake conditions to validate the damping performance of the RB-EDC. The seismic isolation system consists of the RB-EDC and an RC column identical to the RC column specimen. The results indicate that, compared to the RC column specimen, the column in the seismic isolation system specimen significantly reduces crack distribution ranges, rebar strain, concrete strain, and displacement at the column top under seismic actions. The RB-EDC exhibits significant energy dissipation capacity even during frequent earthquakes, demonstrating effective damping performance. However, the residual displacement of the RB-EDC increases with seismic intensity, which may impact the damping performance of the bearing in future potential earthquakes, indicating the need for further redesign to incorporate self-centering capacity.

Research on a Bridge Hybrid Isolation Control System Based on PID Active Control and Genetic Algorithm Optimization

A bridge hybrid isolation system, integrating both active and passive control strategies, is proposed and investigated to enhance seismic performance. The system is modeled as a two-layer structure, with the upper layer subjected to active control via a Proportional–Integral–Derivative (PID) controller, and the lower layer employing a conventional passive base isolation system. The displacement response of the superstructure is minimized by the control forces generated by the PID controller, which also accounts for the reaction forces transmitted to the lower isolation layer. To optimize the controller’s performance, a genetic algorithm is implemented for real-time tuning of the PID parameters. Numerical simulations, conducted using the Newmark method, are employed to assess the influence of active control on the lower isolation system. The results reveal that, while active control increases the peak displacement of the superstructure to some extent, it significantly prolongs the structural period, thus enhancing the system’s overall seismic resilience and stability.

Assessing the Partial Hessian Approximation in QM/MM-Based Vibrational Analysis.

The partial Hessian approximation is often used in vibrational analysis of quantum mechanics/molecular mechanics (QM/MM) systems because calculating the full Hessian matrix is computationally impractical. This approach aligns with the core concept of QM/MM, which focuses on the QM subsystem. Thus, using the partial Hessian approximation implies that the main interest is in the local vibrational modes of the QM subsystem. Here, we investigate the accuracy and applicability of the partial Hessian vibrational analysis (PHVA) approach as it is typically used within QM/MM, i.e., only the Hessian belonging to the QM subsystem is computed. We focus on solute-solvent systems with small, rigid solutes. To separate two of the major sources of errors, we perform two separate analyses. First, we study the effects of the partial Hessian approximation on local normal modes, harmonic frequencies, and harmonic IR and Raman intensities by comparing them to those obtained using full Hessians, where both partial and full Hessians are calculated at the QM level. Then, we quantify the errors introduced by QM/MM used with the PHVA by comparing normal modes, frequencies, and intensities obtained using partial Hessians calculated using a QM/MM-type embedding approach to those obtained using partial Hessians calculated at the QM level. Another aspect of the PHVA is the appearance of normal modes resembling the translation and rotation of the QM subsystem. These pseudotranslational and pseudorotational modes should be removed as they are collective vibrations of the atoms in the QM subsystem relative to a frozen MM subsystem and, thus, not well-described. We show that projecting out translation and rotation, usually done for systems in isolation, can adversely affect other normal modes. Instead, the pseudotranslational and pseudorotational modes can be identified and removed.

Study on Dynamic Characteristics of Resilient Mount Under Preload.

Resilient mounts are essential for anti-vibration and shock absorption applications, making accurate predictions of their static and dynamic behaviors critical for effective design and mechanical performance. This study investigates static and dynamic characteristics of resilient mounts to predict their effects. Tension, compression, and shear tests were performed under quasi-static loading conditions to obtain stress-strain cycle curves. This study includes a review of the Yeoh hyperelastic model, which consists of three parameters, and discusses the calibration of these parameters to describe the hyperelastic material behavior. The parameters were validated through numerical analysis by comparing them with experimental results from quasi-static tests on the resilient mount. The dynamic behavior was further analyzed using modal analysis and frequency response simulations under various preload conditions. Results show that increasing preload significantly shifts the transmissibility curves and resonance peaks to lower frequencies. This study offers valuable insights into static and dynamic characteristics of resilient mounts, contributing to the design and optimization of vibration isolation systems for naval applications.

Isolation Performance of the Quasi-Zero Stiffness Isolation System Enhanced by Mixed Tuned Inerter Damper

The low-frequency isolation performance of the transverse spring-rocker quasi-zero stiffness (QZS) isolation system has been demonstrated. However, the QZS isolation system could encounter a deterioration of the low-frequency isolation performance under strong external excitation, due to the hardening phenomenon of its amplitude-frequency response (AFR). To end this problem, a mixed tuned inerter damper (MTID) which combines the advantages of the tuned inerter damper (TID) and the tuned viscous mass damper (TVMD) is proposed in this research. The analytical solution of the AFR of the MTID-QZS isolation system under harmonic excitation is solved by the harmonic balance method (HBM) and verified by numerical method. Whereafter, the corresponding stability analysis of AFR is conducted, and the force transmissibility (FT) of the MTID-QZS is defined to qualify the isolation performance. The effects of the tuning frequency of MTID, the inertance-to-mass ratio, and damping ratios on AFR and FT are conducted, and optimized parameter combinations are suggested to obtain distinguished ultra-low-frequency isolation performance. The comparison among the MTID-QZS system, TID-QZS system, TVMD-QZS system, and QZS system shows that the MTID-QZS system has obvious advantages in suppressing the low-frequency and high-frequency vibration either under strong or weak external excitation.

A Study of Sliding Base Isolation System: A Review

Seismic isolation systems are crucial for protecting structures by minimizing the transmission of acceleration during seismic events, and among the various types, the resilient sliding system, which combines restoring springs and sliders, is highly effective in mitigating seismic impacts. This system controls structural responses by balancing stiffness and friction, ensuring safety while maintaining the functionality of buildings. However, optimizing the design of this system requires carefully selecting combinations of stiffness and the coefficient of friction to achieve low acceleration levels, while simultaneously managing the relative displacement within the isolation system to protect both the structure and its occupants. Excessive displacement may compromise the integrity of the isolation system or cause damage to the structure it is meant to protect. The challenge lies in finding the optimal friction and stiffness levels that provide sufficient energy dissipation and restore forces without allowing displacement to exceed acceptable thresholds. Studies show that restoring forces generated by springs help limit excessive displacements, while sliders dissipate seismic energy, and adjustments in these parameters must account for variations in ground motion intensity and frequency. Thus, a balance between flexibility and resistance is essential in sliding systems to ensure maximum structural safety and occupant protection during earthquakes. This paper reviews different sliding isolation systems which fulfils the requirements of controlling the earthquake and functioning accordingly. It include systems such as PF, FPS, VFPI , CFPI,VFPS,PFPE, VCFPS,VFFPI etc.

Experimental Study on Seismic Performance Evaluation of a Multi-Story Steel Building Model with Rolling-Type Seismic Base Isolation

Critical structures such as hospitals, high-precision manufacturing facilities, telecommunications centers, and fire stations, especially, need to maintain their functionality even during severe earthquakes. In this sense, seismic isolation technology serves as a vital design method for preserving their functionality. Seismic isolators, also known as earthquake isolation systems, are used to reduce the effects of earthquakes on buildings by isolating them from the ground they are located on. By ensuring that less acceleration and force demand is transmitted to the superstructure, both the building and the equipment and the devices in the building are prevented from being damaged by earthquakes. This experimental study aims to conduct vibration tests on a small-scale multi-story steel-building model equipped with a specially designed rolling-type seismic base isolation system. The relationship between the test model and the prototype was achieved by frequency simulation. The tests will be performed on a shake table under six different earthquake accelerations to examine the model’s dynamic behavior. The primary goal is to evaluate the isolation performance of the rolling-type seismic base isolator under seismic loads, with a focus on recording the vibrations at the top of the test building. It has been observed that the isolator placed at the base of the building significantly reduced the peak acceleration and displacement values of the floor motion. Under the most severe earthquake record applied to the shake table, the acceleration at the top of the building with the isolator was found to be reduced by approximately 50%, compared to the non-isolated case.

Chaotic band-gap modulation mechanism for nonlinear vibration isolation systems based on time-delay feedback control

Abstract Systems designed for nonlinear vibration isolation that incorporate chaotic states demonstrate superior capabilities in vibration attenuation, adeptly modulating the spectral constituents of vibrational noise. Yet, the challenge of eliciting low-amplitude chaotic dynamics and perpetuating these states across a diverse array of parameters remains formidable. This study proposes a pioneering strategy and technique for modulating the chaos band by incorporating a time-delayed feedback control mechanism within the framework of nonlinear vibration isolation systems.The investigation commences with an exhaustive analysis of the nonlinear dynamics, shedding light on the principles dictating the evolution of chaos. The study then advances to scrutinize the dynamics of systems with delays to elucidate the chaos-inducing processes engendered by feedback with temporal lags. Building upon the system’s responses, the chaotic performance and the effectiveness of the vibration isolation are crafted. Consequently, the time-delayed feedback control parameters are identified as pivotal design variables, which are then employed to dissect the control mechanisms influenced by the time-delayed feedback on the chaos band. Utilizing the delineated control mechanism, the nonlinear vibration isolation system is precipitously transitioned from a state of stable periodicity to one of chaos, fostering low-amplitude chaotic dynamics across an expansive parameter space, and in turn, resolving the previously stated challenge. Perhaps most significantly, the mechanism for attaining low-amplitude chaos introduced here paves the way for innovative methodologies in the active vibration isolation design of similar systems. Furthermore, it is anticipated to yield theoretical guidance for the manipulation of chaos bands and the formulation of active vibration isolation strategies within the domain of nonlinear vibration isolation systems.

Feasibility and design of nonlinear negative‐stiffness isolating approach for solid‐rocket‐motor‐type structures

AbstractSolid rocket motor (SRM)‐type structures are popular due to their reliability, considering that service safety during transportation can be improved by applying advanced vibration control technologies. In this study, a negative‐stiffness‐enhanced isolation system (NSeIS) with appropriately designed linear and nonlinear properties was developed to vertically isolate SRMs subjected to transportation‐ and deployment‐induced vibrations. The NSeIS design, based on the combination of a negative‐stiffness device and vertical isolator, involved a clear mechanical model, physical realization, and mechanical properties. Parametric analyses were performed on a typical SRM controlled with a linear and nonlinear NSeIS and a conventional isolation system. Subsequently, a feasible parameter domain and design recommendations were deduced. Finally, design cases for the SRM for time‐domain verification were considered. The results revealed that the NSeIS offers a flexible and enhanced isolating effect through the parallel arrangement of the negative‐stiffness device and conventional isolators. For the motor‐type structure, NSeIS ensures marked enhancements in performance and multiple levels of mitigation effects. Thus, compared with a conventional isolator with the same damping, NSeIS achieves a more substantial negative‐stiffness effect for a large displacement response range owing to its nonlinear property. NSeIS can isolate more vibration‐induced energy, thereby suppressing the interface Mises stress, which is essential for SRM‐type structures.