Base Isolation Technique Research Articles

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.

Development of novel low-cost isolator UMELI (unbonded mesh elastomeric layered isolator): experimental investigations

Seismic isolation is a highly efficacious method for reducing the seismic load on structures. This technique is widely adopted to safeguard structures from earthquakes. Despite the promising results demonstrated by numerous isolation techniques, their implementation remains a significant challenge, particularly in developing countries, due to the high costs associated with manufacturing. Therefore, a novel and affordable base isolation technique has been proposed, namely unbonded mesh elastomeric layered isolator (UMELI). UMELI consists of steel mesh sandwiched between the unbonded layers of elastomers, resulting in an affordable isolator to be used for lightweight, low-rise structures. One of the crucial characteristics of this novel isolator is that it does not require a specialised manufacturing process unlike other elastomeric isolators. In the present study, experimental investigations are conducted to evaluate the dynamic characteristics such as dynamic vertical stiffness, equivalent lateral stiffness, and equivalent viscous damping ratio of UMELI. Its characteristics were studied for different layered isolators and are compared with the unreinforced elastomeric isolator. The investigations have demonstrated the effectiveness of the UMELI by increasing its vertical stiffness and reducing lateral stiffness, thereby enhancing the isolation period with the addition of a steel mesh layer.

Earthquake Resisting Building by using Base Isolation

Abstract: Natural disasters have been always been a part of human life since the beginning of time, causing destruction to our lives and properties. Earthquake plays a major role in wreaking this havoc upon us. Various challenges have occurred to withstand structures on earth due to sudden moment of ground it also results in collapse of structure, due to inappropriate design consideration of structure without any seismic resistance. Various techniques to make the building earthquake resistant as well as various shapes and materials are being considered to achieve required strength to resist seismic forces. Various techniques like shear walls, bearings and base isolation are used to withstand the structure against seismic forces. In this project we have used base isolation technique, it is also known as seismic base isolation or base isolation system is a prominent technique to protect the structure against earthquake.

The Role of a Simple Inerter in Seismic Base Isolation

The present study investigates the role of a simple inerter in supplemental devices for possible implementation in the mature seismic base isolation technique. Firstly, the response of the base-isolated structure with an optimally tuned mass damper inerter (TMDI) is investigated to see the tuning effects. The time required to tune the TMDI was found to be significantly longer than the duration of a strong-motion earthquake. There was still a reduction in the response of the isolated structure, which is primarily due to the added damping and stiffness (ADAS) of TMDI and not because of the tuning effects. Hence, it is proposed that the corresponding ADAS of the TMDI be directly added to the isolation device. Secondly, the response of the base-isolated structures to the fluid inerter damper (FID) is studied. It was observed that the inerter of the FID does not influence the displacement variance of an isolated structure under broadband earthquake excitation. It implies that the response of the isolated structure to FID is primarily controlled by its counterpart fluid damper (FD). The performance of optimal TMDI, ADAS, FID, and FD to mitigate the seismic response of the flexible multi-story base-isolated structure under real earthquake excitations is also investigated. In terms of suppressing the displacement and acceleration responses of the isolated structure, it has been found that TMDI and ADAS perform similarly. Comparing the response of the isolated structure with FID and FD demonstrated that the inerter in the FID has detrimental effects on the isolated structures, in which the top floor’s acceleration and base shear are substantially increased.

A 3-DOF system for preliminary assessments of the interaction between base isolation (BI) technique and soil structure interaction (SSI) effects for low-rise buildings

Base isolation technique is based on two mechanisms: period elongation and damping increase that may considerably improve the structural performance under earthquakes. However, the effectiveness of BI may be significantly reduced by the deformability of the foundation soil and thus by soil structure interaction (SSI) effects. In this regard, considering the role of the mutual interaction between BI and SSI becomes fundamental to realistically design structural systems. In literature, the assessment of the mutual role of BI and SSI is conducted with advanced numerical simulations that require realistic definitions of the non-linear properties of the structures, the isolation system and of the soil layers. However, these methods are extremely time-consuming and more expeditious methodologies are necessary. In this paper a 3-DOF system is proposed to perform preliminary assessments for design purposes. Parametric case studies have been proposed to demonstrate the potentiality of the proposed method to represent the cases where the beneficial effects of BI are reduced and eventually when BI technique becomes detrimental.

An expeditious framework for assessing the seismic resilience (SR) of structural configurations

The assessment of the Seismic Resilience (SR) has become a fundamental issue in Structural Engineering to ensure rapid and efficient recovery to earthquake scenarios. Even if there are methodologies that assess SR, most of them are significantly time-consuming. In this paper, a framework for simplified assessments of SR is proposed based on the existing literature. The probability-based method of fragility curves is applied to estimate the losses and a novel definition of the recovery model is herein proposed. A case study is discussed to apply the proposed framework to two configurations: a fixed-base and a base-isolated structural system. The state-of-the-art platform Opensees has been applied to calculate the non-linear performance of the structures. The longitudinal drift ratio was chosen as the representative parameter to develop fragility curves and thus to quantify SR. The response of the 200 analyses (100 for each system) shows the benefit of applying base isolation technique in terms of SR, used as a comprehensive parameter to compare the two solutions. The proposed approach may be helpful for many stakeholders and decision makers for pre- and post-earthquake assessments.

Enhancing the Seismic Response of Residential RC Buildings with an Innovative Base Isolation Technique

The prediction of the magnitude and impact of forthcoming earthquakes remains an elusive challenge in the field of science. Consequently, extensive research efforts have been directed toward the development of earthquake-resistant design strategies aimed at mitigating building vibrations. This study focuses on the efficacy of fluid viscous dampers (FVDs) in augmenting the seismic response of a low-rise residential reinforced-concrete building, which is base-isolated, using high–damping rubber bearings (HDRBs). The structural analysis employs a non-linear approach, employing ETABS v16 software for building modeling and conducting non-linear dynamic analysis using artificial accelerograms specific to Algeria. Three distinct connection configurations to the building’s base are investigated: (1) a fixed-base structure; (2) a structure isolated by HDRBs; and (3) a structure isolated utilizing a novel parallel arrangement of HDRBs in conjunction with FVDs. Comparative evaluation of these configurations reveals noteworthy findings; the results demonstrate that the base isolation system, comprising HDRBs and FVDs, significantly diminishes the base shear force by over 80% and reduces acceleration by 54% while concurrently increasing displacement by 47%. These findings underscore the effectiveness of incorporating FVDs in conjunction with HDRBs as a means to enhance the seismic response of reinforced concrete buildings. This study showcases the potential of such structural analyses to contribute to the development of earthquake-resistant design approaches, providing valuable insights for architects and engineers involved in constructing resilient buildings in seismically active regions.

A Review on the Modelling Techniques of Liquid Storage Tanks Considering Fluid–Structure–Soil Interaction Effects with a Focus on the Mitigation of Seismic Effects through Base Isolation Techniques

Globally, tanks play a major part in the provision of access to clean drinking water to the human population. Beyond aiding in the supply of fresh water, tanks are also essential for ensuring good sanitary conditions for people and for livestock. Many countries have realized that a robust water supply and a robust sanitation infrastructure are necessary for sustainable growth. Therefore, there is large demand for the construction of storage tanks. Further, liquid storage tanks are crucial structures which must continue to be operational even after a catastrophic natural event, such as an earthquake, to support rehabilitation efforts. From an engineering point of view, the various forces acting on the tanks and the behaviour of the tanks under various loads are important issues which need to be addressed for a safe design. Analyses of the tanks are challenging due to the interaction between the fluid and tank wall. Thus, researchers have conducted several investigations to understand the performance of storage tanks subjected to earthquakes by considering this interaction. This paper discusses the historical development of various modelling techniques of storage tanks. The interaction with the soil also influences the behaviour of the tanks, and hence, in this paper, various modelling approaches for soil structure interaction are also reviewed. Further, a brief history of various systems of base isolation and modelling approaches of base-isolated structures are also discussed in this article.

Serviceability performance of buildings founded on rubber–soil mixtures for geotechnical seismic isolation

ABSTRACT Base isolation is a low-damage seismic design strategy that can be used for constructing resilient structures. Geotechnical seismic isolation (GSI) is a new category of emerging base isolation techniques that has attracted global interest in the past decade. Research on GSI based on rubber-soil mixtures (RSM) has focused on structural performance under earthquake actions, whilst there are concerns over the serviceability limit states (SLS) requirements in relation to (i) human comfort under strong winds and (ii) ground settlement under gravity, which may induce cracking and durability issues in structures. This article presents the first study on the serviceability performance of buildings constructed with the GSI-RSM system. The finite element model of a coupled soil-foundation-structure system has been validated by data recorded from geotechnical centrifuge testing. The numerical estimates of ground settlement have also been compared with analytical predictions. It is concluded that the GSI-RSM system can satisfactorily fulfill the SLS requirements.

Seismic performance of advanced three-dimensional base-isolated nuclear structures in complex-layered sites

The application of three-dimensional (3D) base isolation for nuclear structures is advantageous. In this study, an advanced 3D base isolation technique was developed and the nonlinear seismic response of 3D base-isolated nuclear structures in complex layered sites was investigated using a global method. The study first designed a novel 3D isolation system, including horizontal and vertical isolation, based on the disc spring theory, which can flexibly adjust the structural stiffness and vertical bearing capacity. To verify the applicability of 3D base isolation, the dynamic behaviour of a 3D base-isolated nuclear island building in complex-layered sites subjected to beyond-design basis ground motion was investigated using a proposed high-precision simulation program of soil-structure interaction (SSI) based on the global method. The findings demonstrate that in complex-layered sites, the SSI increases the horizontal floor response spectra (FRS) but decreases the vertical FRS of 3D base-isolated nuclear power plants, and both the horizontal and vertical isolation rates remarkably decrease. The influence of the SSI becomes more evident as the intensity of the ground motion increases. The proposed 3D base isolation system exhibits excellent isolation effects. When the vertical stiffness is reduced, the vertical isolation effect becomes more significant. However, the adverse rocking motion of the island building should be effectively controlled. The research results support the practical application of 3D base isolation technology for nuclear structures located in complex-layered sites with high seismic intensities.

Development of low-cost base isolation technique using multi-criteria optimization and its application to masonry building

Seismic isolation devices made of rubber have been adopted globally to protect buildings and bridges from seismic events. Recent research has focused on many low-cost rubber-based isolation devices for seismic hazard mitigation. While some techniques have demonstrated promising results, their practical application to buildings in seismic-prone rural parts of developing countries remains challenging. The present study proposes a low-cost base isolation technique that is viable and feasible for masonry buildings. The primary objective of the present study is to investigate the use of unreinforced rubber as a seismic base isolator. Initially, the rubber samples with different hardness were procured and tested for Hyperelastic and viscoelastic coefficients. These properties were used to model the rubber isolator in ABAQUS. A parametric study was conducted, and optimized rubber properties were obtained using the weighted sum approach. The optimized rubber is numerically validated with the experiment. The rubber isolator was designed and then modeled to an experimentally validated one-story masonry building. The behavior of building with and without proposed isolators is evaluated by subjecting them to seven spectrum-matched ground motions. A significant reduction in seismic response in terms of roof acceleration is observed. This study indicates the scope for using unreinforced rubber as an isolator for masonry buildings.

Life-cycle seismic resilience assessment of isolated bridges equipped with different isolation systems

Damage to bridges during a seismic event can cause significant disruption to post-event activities. In addition to natural hazards, the deterioration of bridges over their lifespan also significantly impacts seismic performance. This study intends to evaluate the overall life-cycle resilience performance and post-seismic loss analysis of bridges equipped with two different isolation systems including lead rubber bearings and friction pendulum bearings. Two different bridge configurations and three different suites of earthquakes representing possible seismic hazards at the bridge site are considered. The comparative resilience assessment and cost analysis represent the base-isolation technique’s adequacy, effectiveness and cost-effectiveness. Statistical analysis is conducted to identify the parameters affecting the seismic resiliency, loss and cost analysis of base-isolated bridges. The results show that seismic resilience, loss and cost analysis are more sensitive to the type of ground motions, geometric shape of the bridge and type of isolation bearings, respectively.

Seismic performance of indoor substation RC frames with combined base isolation techniques

In order to investigate the seismic performance of indoor RC substations with combined base isolation technique under far-field earthquakes and near-fault earthquakes, a 1/4 scaled three-story RC frame model was prepared for shaking table tests. Three different model configurations were considered, namely the non-isolated model (control model), the mono-isolated model (model with lead rubber bearings), and the combined isolated model (model with lead rubber bearings and viscous dampers). Scaled transformers and GISs were also installed on the model floors to consider the influence of the electrical equipment. Typical far field and near fault seismic waves, in this study the El Centro wave and the ChiChi wave, respectively, up to a PGA of 0.44 g were used as excitations. It was found that LRBs worked desirably for the RC model under the El Centro wave while less effective under the ChiChi wave. The acceleration responses (roof), the inter-story shear force (1F) and the inter-story drift (2F) were reduced by use of the LRBs at most by 21%, 51% and 26%, respectively, with respect to the non-isolated model under the El Centro wave. However, under the ChiChi wave irregular torsional behavior was observed and the isolation layer displacement reached 88% of the limit value. Combined use of LRBs and VDs effectively reduced the seismic responses of the RC model under the ChiChi wave. In particular, the isolation layer displacement was reduced by 15% and the torsional displacement ratio was reduced to less than 1.15, with respect to the model with LRBs only. Considerable equipment-structure interaction was found in the RC indoor substations and increased the acceleration and the displacement responses by up to 21% and 22%, respectively, given the position and mass of the equipment in this study. Besides, the LRBs and VDs were found to be effective to reduce the equipment-structure interaction.

Reliability analysis of structures with inerter-based isolation layer under stochastic seismic excitations

Reliability analyses on various control devices are of vital importance in examining and quantifying their practical feasibility and effectiveness. In specific, an emerging base isolation technique using a tuned inerter damper (TID) draws researchers’ attention given some of its unique merits, such as the compact damper size, lightweight, and the fact that it will not compromise structural stiffness when the system is static and thus prevents the long-term creeping issue. To justify its feasibility and robustness in face of random earthquake excitations, this paper presents both (1) a simulation-based stochastic dynamic response analysis, and (2) a reliability analysis of a benchmark reinforced concrete (RC) structure with a TID isolation layer. It is found that although seismic randomness shall substantially affect the structural dynamic responses, the introduction of a TID isolation layer to the structure will significantly alleviate this effect and subsequently enhances the overall system robustness, which can be parallelly identified from the notable different features between their corresponding probability density evolutions. In addition, the reliability of the RC structure is also drastically improved owing to the introduction of the TID isolation layer, which highlights its effectiveness and sheds light on its great potential in future industrial applications.

Comparative Study of the Non-Linear Dynamic Behaviour of Different Seismic Isolation Systems

To mitigate the effect of earthquake on the structure, the base isolation technique is the best alternative as a seismic protection system. In this research, a two-degree-of-freedom (2DOF) equivalent model is modelled based on a real eight-level reinforced concrete structure damaged by the Boumerdes earthquake in 2003 is presented. The basic isolation systems considered are four models namely: the first system is a high damping isolator (HDBR), the second system is the friction pendulum isolator (FPS). The third model of the base isolation system is a non-linear model with two horizontal and rotational stiffness springs (SHRS), and finally the last model presents a bilinear spring (SB). The isolators are designed according to the UBC-97 code. Earthquake recordings from Dar-El-Beida of the 2003 Boumerdes earthquake were used as seismic load. A dynamic analysis of the comparative temporal responses of the structure was performed by comparing its dynamic behaviour with that of the fixed base structure. The results obtained reveal a reduction in base shear, stage drift and stage acceleration and an increase in displacement and time period for the structure isolated at the base. The results are presented in tables and graphs.

Analytical Study of Base Isolation- A Review

Now a days the rate of happening of seismic events increasing and due to that so many structures got collapsed or damaged. In order to reduce the damage to structures during earthquakes, now a days the base isolation system is widely adopted and used over the world. This paper makes a wide review on the various base isolation techniques adopted and used. Different types of isolating bearings and materials used in it are reviewed. Here the review is done for the isolation system in normal R.C buildings (regular and irregular in plan) and also for bridges. The effect of base isolation system on some historic structures is also reviewed. The various advantages and disadvantages of different isolating bearings are reviewed. Here the effect of temperature on some isolating devices are also reviewed.

Seismic Performance of Elastomeric and Sliding Friction Isolation System

The base isolation technique is widely used in the isolation of structures for providing efficient protection to structures concerning different loadings. This study aims to evaluate comparative performance and inelastic responses of the base-isolated structure for two types of isolation systems under the Far-field and Near-field earthquake. For this purpose, seismic response quantities like base shear, peak ?oor displacement, absolute acceleration, and isolator displacement for ten-story reinforced concrete building frame base isolated by lead rubber bearings (LRBs) are evaluated and compared with the seismic response of the same structure base isolated by Friction Pendulum Bearing Isolator. Nonlinear time history analysis is carried out to investigate the inelastic behavior of the base-isolated structure. The building frame was designed according to IS1893:2016 seismic code and IS 456:2000. To represent a wide range of assessments, a 10 storey building frame taking identical isolation parameters for elastomeric and sliding isolation system was analyzed in SAP 2000. It was observed that the responses of both the isolation system are nearly the same for all the three earthquakes.

A frequency-dependent variable damping control method for base-isolated structures under ground motions with different frequency characteristics

The base isolation technique is commonly adopted to protect important structures from earthquake damages. Typically, a high damping ratio for the base isolation layer is useful in reducing the structure's resonance effect under low-frequency (long-period) ground motions, and a low damping ratio is preferred in minimizing the acceleration response under high-frequency (short-period) ground motions while not causing significant displacement response. To realize optimal control for base-isolated structures under ground motions with different frequency characteristics, the semi-active control is adopted and a frequency-dependent variable damping (FVD) control method based on a transmissibility weighted fast Fourier transform (TWFFT) spectrum is newly proposed. The FVD control method considers the influences of different frequency components of ground motions on base-isolated structures by developing the TWFFT spectrum of the detected ground accelerations. A series of shaking table tests for a base-isolated steel frame structure with semi-active control were carried out to evaluate the effectiveness of the FVD control method. The test results demonstrated that the FVD control method could realize optimal control of the structure under various types of ground motions, and it was more effective than the ON-OFF control method which only considered the dominant frequency characteristics of the ground motions.

Sliding Isolation Systems: Historical Review, Modeling Techniques, and the Contemporary Trends

Base isolation techniques have emerged as the most effective seismic damage mitigation strategies. Several types of aseismic devices for base isolation have been invented, studied, and used. Out of several isolation systems, sliding isolation systems are popular due to their operational simplicity and ease of manufacturing. This article discusses the historical development of passive sliding isolation systems, such as pure friction systems, friction pendulum systems, and isolators with other sliding surface geometries. Moreover, multiple surface isolation systems and their behavior as well as the effectiveness of using complementary devices with standalone passive isolation devices are examined. Furthermore, the article explored the various modeling techniques adopted for base-isolated single and multi-degree freedom building structures. Special attention has been given to the techniques available for modeling the complex phenomena of sliding and non-sliding phases of sliding bearings. The discussion is further extended to the development in the contemporary areas of seismic isolation, such as active and hybrid isolation systems. Although a significant amount of research is carried out in the area of active and hybrid isolation systems, the passive sliding isolation system still has not lost its appeal due to its ease of adaptability to the structures.

Dynamic analysis of RCC framed structure considering effect of viscous dampers and base isolation

Due to the overall scarcity of space and the rising population, high-rise buildings have become more common. Although we have RCC structure solutions fortall structures, the deadweight of RCC structural components is larger owing to the massive dimension of the building's elements and the great densities of material. Engineers are using a superior structural technology called Steel-Concrete Composite Structure after detecting challenges and hurdles in the high-rise construction sector. Concrete, which is beneficial in carrying compressive loading, and steel, which has good tensile strength, are used to create structural components. The combo of such materials increases the ductility of the structure over RCC constructions. Damping is critical in seismic-resistant construction design. The damping measures lessen approaching oscillations on the superstructure itself, hence preventing destruction. Base isolation (BI) is a widely used approach for shielding structures from the disastrous impacts of earthquakes. The placement of an isolation device at the foundation of a structure greatly extends the natural time period of the structure, reducing the potential of resonance frequency and therefore improving the seismic response of buildings. This study analyzes a G + 10 Story building using composite columns, viscous dampers, and base isolation techniques. The focus of the paper is to check the efficacy of viscous dampers and base isolation techniques for controlling the response of the composite column structure. After doing the study, composite columns and viscous damper combination reduce the Story displacement and drift values but increase the base shear values. But this problem can be omitted by using base isolation in combination with these two. After the study, it’s had been found that a combination of composite columns, viscous dampers, and a base isolation mechanism is highly helpful in controlling the seismic response of the structure.