Use Of Seismic Isolation Research Articles

Concept of combined strain-stress state control of long span structures

Purpose: Argumentation of necessity of special protective system design to protect structures in seismic zones and remote areas from specific loads. Such protective system combines seismic isolation and internal force control systems.Research findings: Restrictions of long-span structures construction are reviewed. Such restrictions are caused by building conditions embodied in National Building Codes and Standards. Combined and separate use of seismic isolation and internal force control systems is a critical specific load protection. Present inventions and experience in the field of seismic isolation and internal force control systems are reviewed.Value: The article determines problems of protective system design based on the control for combined strain-stress state.

Seismic Performance Evaluation of Multi-Storey Residential Building with Friction Pendulum Bearings: Indonesia case study

The methodology for seismic performance evaluation of a residential building in Indonesia with the use of seismic isolation is considered. An 8-storey reinforced concrete frame residential building with shear wall structural system was selected as a case study. Nonlinear methods of seismic response analysis were used to calculate the response of the structure: nonlinear static (Pushover) and Nonlinear-Time History Analysis, NLTHA. The analysis is performed in STERA 3D freeware. The nonlinear time history analysis was performed for seven pairs of horizontal components of earthquake ground motions, selected according to the parameters of possible earthquakes for the considered site (Bandung city). The selected earthquake records were modified using the spectral matching procedure for design spectrum. Friction-pendulum bearings developed by Nippon Steel Corporation of Japan were used as seismic isolation. The results of nonlinear time history analysis show that shallow earthquakes result in greater damage compared to megathrust earthquakes, with both scenarios providing a life safety (LS) performance level. The use of seismic isolation can reduce seismic loads, as evidenced by the reduction in top-level accelerations and shear forces at the base.

عملکرد سازه ی مجهز به جداساز لرزه یی طبقه و آلیاژهای حافظه دار شکلی با پایه ی آهنی

در سال‌های اخیر، در ساختمان‌های خاص به طراحی جداسازهای لرزه‌یی در طبقات بالاتر از پایه که جداساز طبقه نامیده می‌شود، بسیار توجه شده است. با وجود این، جداسازهای لرزه‌یی با محدودیت‌هایی، از قبیل: ناپایداری در تغییرشکل‌های بزرگ، جابه‌جایی پسماند و غیره پس از زلزله‌های شدید هستند. استفاده از آلیاژهای حافظه‌دار شکلی با توجه به خواص منحصر به فردی که دارند، به عنوان راه حلی مناسب برای غلبه بر این نواقص درنظر گرفته شده‌اند. هدف از پژوهش حاضر، بررسی اثر ترکیب آلیاژهای حافظه‌دار شکلی و جداسازها در سازه و تأثیر آن‌ها در کاهش پاسخ لرزه‌یی سازه بوده است. به همین منظور، سازه‌ی چندطبقه‌ی فولادی همراه با ترکیب جداساز لرزه‌یی طبقه و آلیاژهای حافظه‌دار شکلی با پایه‌ی آهنی و با استفاده از نرم‌افزار O‌p‌e‌n‌S‌e‌e‌s مدل‌سازی و ارزیابی شده است. نتایج به‌دست آمده نشان داده است که استفاده از آلیاژهای مذکور در جداسازهای لرزه‌یی طبقه باعث کاهش جابه‌جایی در تراز جداساز می‌شود و می‌توان آن را به‌عنوان سامانه‌یی مطلوب در مهار سازه‌ها در نظر گرفت.

Advantages of seismic isolation of Building and structures

The article discusses the benefits of using seismic isolation for buildings and structures. The results of many studies of major world earthquakes are presented. The use of seismic isolation reduces the effects of earthquakes and increases the safety margin and safety of buildings and structures.

Reduction of seismic loads for transport construction facilities using dry friction elements

In the city of Almaty, a seismically insulated building using dry friction elements was built at a special training ground. An engineering-seismometric service station is installed on the building. The dynamics of the building under the influence of accelerograms of real earthquakes in the city of Almaty is being studied. Accelerograms of the Baysorun earthquake recorded on solid soils and the Zhalanash-Tyup earthquake recorded on clay soils are used. Spectral coefficients are obtained for various values of the dry friction coefficient. It is shown that on solid soils the use of seismic isolation with dry friction elements based on fluoroplastic gaskets reduces seismic loads by half. On clay soils, the use of such a system of seismic isolation seems inappropriate. The results of the work can be used for seismic isolation of transport infrastructure facilities.

Study of Dimension Variation Effect on a Batter Piled Wharf Structure with Seismic Isolation Systems

In a conventional wharf design, batter piles are incorporated in the design as a primary lateral resistance element, however in recent years it is mostly discouraged to use batter piles in the design of wharf structure, especially in higher seismic zone. The use of seismic isolation in the design of wharf structure has been introduced since 2005 in UFC 4-152-01 code as an alternative design for wharf structure, from several studies it is shown that the usage of seismic isolation systems in wharf design has offered many benefits either in new design or structure retrofitting design. The objective of this research is to study the application of seismic isolation system on wharf structure with batter piles, with study case of the wharf design on Kendari, Sulawesi Tenggara, Indonesia. This objective will be achieved by comparing the length per width (L/W) ratio of wharf structure model to evaluate base reaction, natural period and deflection of structure, from these results, a clearer understanding about the advantages of seismic isolation system in wharf structure, so it will be encouraging the application of seismic isolation systems.

Seismic Isolation: An Effective Technique for the Seismic Retrofitting of a Reinforced Concrete Building

Seismic isolation, usually applied for new structures, is used for the seismic upgrade of a five-storey reinforced concrete building. The building is a frame structure, representative of the residential buildings designed in the 1960s and 1970s in Greece and southern Europe, and thus following an older generation of codes. Response spectrum analysis, performed for the seismic assessment of the structure, using EC8 code provisions, showed poor structural performance and inadequate capacity of many structural members. A seismic upgrade of the structure is thus needed and the use of friction-pendulum system bearings, placed above the foundation level, is examined. A series of linear and non-linear analyses is performed and the results show a major improvement in the overall seismic performance of the building, while interventions are required only at the ground floor and foundation levels. The effectiveness and limitations in the applicability of this retrofitting procedure are discussed. It is concluded that the seismic retrofitting of existing buildings through the use of seismic isolation is an effective approach. It results in an enhanced performance level compared to conventional approaches; therefore, it should always be considered as an alternative to conventional retrofitting techniques.

Earthquake-Induced Pounding of Medium-to-High-Rise Base-Isolated Buildings

During earthquakes, out-of-phase vibrations in adjacent buildings with limited distance may cause pounding between them. In recent years, the use of seismic isolation has expanded considerably as an effective approach to reduce seismic damage. However, the isolated building experiences large displacements during earthquakes, and there is a possibility of collisions with adjacent structures. The research on earthquake-induced pounding of base-isolated buildings has been mainly focused on interactions between low structures. In this paper, the influence of structural pounding on the response of medium-to-high-rise base-isolated buildings is investigated under different ground motions. The analysis has been focused on collisions between two insufficiently separated five-story and eight-story base-isolated and fixed base buildings aligned in three different configurations. The results of the study indicate that structural pounding may significantly increase the response of medium-to-high-rise base-isolated buildings during earthquakes. Moreover, substantial dependence of the structural behavior on the gap size between structures has been observed. The general trend shows the reduction in the pounding-involved response with the increase in the gap size value. The results indicate that the increase in the response of the base-isolated building is larger when the height of the structure is bigger. They also show that larger amplifications of peak accelerations of the upper stories can be expected due to collisions. On the other hand, the amplifications of the story shears have not shown any specific trend for different stories of the analyzed base-isolated building.

Shaking table tests of bridge model with friction sliding bearings under bi-directional earthquake excitations

The widespread use of seismic isolation to protect structures from damage has already been proven as an effective and economical method. In order to investigate the seismic performance and isolation effect of isolated bridge with the traditional friction pendulum bearing (FPB) and the novel triple friction pendulum bearing (TFPB), the force–displacement hysteretic relationships of FPB and TFPB were validated by the displacement-controlled tests, and the shaking table tests were carried out on a 1/10 scaled simple-supported bridge model with FPBs and TFPBs under bi-directional earthquake excitations. The effects of the friction coefficients and the radius of the TFPB on the seismic responses were analysed using the extensive experimental results. The experimental data and the numerical results show that the TFPB can be reliably used for the passive device to control the seismic response of the bridge, which could satisfy the demand of performance-based seismic design philosophy in high seismicity regions. In addition, the results illustrate that the bi-directional interaction of the TFPB has effects on the dynamic responses of the bridge. If the bi-directional interaction is ignored, the deck displacements are underestimated, which can be crucial from the design point of view.

On the Efficiency of Use of Seismic Isolation in Antiseismic Construction

The main issues of evaluating the efficiency of use of the seismic isolation systems as a reliable means of seismic protection of buildings and structures in seismically hazardous regions have been analysed. Specific characteristics of the most common types of seismic isolation in case of seismic load considered. It is shown that these protection systems are now becoming more common, without their respective justification. In this regard, there is a need to develop special recommendations for the use of seismic insulation in the construction of buildings and structures for various purposes. At the same time, special attention is paid to the effective conFigureuration of seismic isolation and the role of damping in it. The possibility of application of the considered protection should include: an assessment of the seismological situation of the construction area, technical and economic analysis of the choice of the type of seismic insulators, a complex of computational, theoretical and experimental studies.

Applicability of Commercial Software for Bridge Design with Consideration of Seismic Loading Effects

The construction of bridges with use of seismic isolation is a less-used concept in Slovakia and the Czech Republic. The concept of seismic isolation of bridges is a way of protecting bridge construction without damaging the pillars and substructure unlike the currently used methodology of consideration and development of plastic joints. When using this concept correctly, it is possible to prevent serious damage of construction and greatly reduce economic losses. Creation of a FEM (Fine Element Method) model, that is capable of correct description of the bridge behavior during a seismic event is often problematic. In this paper, the features of designing and modeling of bridge constructions with use of seismic insulation based on elastomeric bearings are presented. Furthermore, the calculations of stiffness constants required for numerical modeling are presented as well. In this paper are described methods of modeling of seismic isolations in a commonly and commercially available FEM based software. The work also contains a comparison of possibilities as well as limits of these programs. We further present recommendations for correct modeling by use of nonlinear material properties or elastic bonds between elements.

Probabilistic performance‐based optimum design of seismic isolation for a California high‐speed rail prototype bridge

SummaryPrevious comparison studies on seismic isolation have demonstrated its beneficial and detrimental effects on the structural performance of high‐speed rail bridges during earthquakes. Striking a balance between these 2 competing effects requires proper tuning of the controlling design parameters in the design of the seismic isolation system. This results in a challenging problem for practical design in performance‐based engineering, particularly when the uncertainty in seismic loading needs to be explicitly accounted for. This problem can be tackled using a novel probabilistic performance‐based optimum seismic design (PPBOSD) framework, which has been previously proposed as an extension of the performance‐based earthquake engineering methodology. For this purpose, a parametric probabilistic demand hazard analysis is performed over a grid in the seismic isolator parameter space, using high‐throughput cloud‐computing resources, for a California high‐speed rail (CHSR) prototype bridge. The derived probabilistic structural demand hazard results conditional on a seismic hazard level and unconditional, i.e., accounting for all seismic hazard levels, are used to define 2 families of risk features, respectively. Various risk features are explored as functions of the key isolator parameters and are used to construct probabilistic objective and constraint functions in defining well‐posed optimization problems. These optimization problems are solved using a grid‐based, brute‐force approach as an application of the PPBOSD framework, seeking optimum seismic isolator parameters for the CHSR prototype bridge. This research shows the promising use of seismic isolation for CHSR bridges, as well as the potential of the versatile PPBOSD framework in solving probabilistic performance‐based real‐world design problems.

Design response spectra-compliant real and synthetic GMS for seismic analysis of seismically isolated nuclear reactor containment building

Due to the severe impacts of recent earthquakes, the use of seismic isolation is paramount for the safety of nuclear structures. The diversity observed in seismic events demands ongoing research to analyze the devastating attributes involved, and hence to enhance the sustainability of base-isolated nuclear power plants. This study reports the seismic performance of a seismically-isolated nuclear reactor containment building (NRCB) under strong short-period ground motions (SPGMs) and long-period ground motions (LPGMs). The United States Nuclear Regulatory Commission-based design response spectrum for the seismic design of nuclear power plants is stipulated as the reference spectrum for ground motion selection. Within the period range(s) of interest, the spectral matching of selected records with the target spectrum is ensured using the spectral-compatibility approach. NRC-compliant SPGMs and LPGMs from the mega-thrust Tohoku earthquake are used to obtain the structural response of the base-isolated NRCB. To account for the lack of earthquakes in low-to-moderate seismicity zones and the gap in the artificial synthesis of long-period records, wavelet-decomposition based autoregressive moving average modeling for artificial generation of real ground motions is performed. Based on analysis results from real and simulated SPGMs versus LPGMs, the performance of NRCBs is discussed with suggestions for future research and seismic provisions.

Transport Interchanges Design Features in Seismically Dangerous and Densely Built-Up Areas

The article describes design peculiar properties of multi-level transport interchange in Karasunsky administrative district of the city of Krasnodar city with a roundabout location at the intersection at a higher level and organization of tram rail traffic in ramp. The interchange is designed with maximum convenience for drivers and passengers of all modes of transport. The project combines modern technological solutions, which is allowed to realize project in a seismically dangerous area in conditions of dense building. The use of seismic isolation and strengthening of the structure with proper design ensures the reliability of structures and the absence of necessary rehabilitation works after an earthquake.

An alternative approach for the seismic rehabilitation of existing RC buildings using seismic isolation

SummaryUsually, buildings with seismic isolation are designed to comply with an operational building performance level after strong earthquakes. This approach, however, may limit the use of seismic isolation for the seismic rehabilitation of existing buildings with low lateral strength or substandard details, because it often requires invasive strengthening measures in the superstructure or the use of expensive custom‐made devices. In this paper, an alternative approach for the seismic rehabilitation of existing buildings with seismic isolation, based on the acceptance of limited plastic deformations in the superstructure under strong earthquakes, is proposed and then applied to a real case study, represented by a four‐storey RC frame building. Nonlinear response‐time histories analyses of an accurate model of the case‐study building are carried out to evaluate the seismic performances of the structure, comparing different rehabilitation strategies with and without seismic isolation. Initial costs of the intervention and possible (future) repair costs are then estimated. Based on the results of this study, values of the behavior factor (i.e. response modification factor) higher than those adopted in the current codes for base‐isolated buildings are tentatively proposed. Copyright © 2015 John Wiley & Sons, Ltd.

Seismic Rehabilitation of Existing Reinforced Concrete Buildings with Seismic Isolation: A Case Study

The use of seismic isolation for the seismic rehabilitation of existing buildings is very attractive but often very tricky due to several aspects related to its implementation. In this paper, a case study of seismic rehabilitation of a high-rise residential building with seismic isolation is presented. The building under consideration is located in southern Italy and it is placed next to another building from which it is separated by a gap of 400 mm. In the paper, all the steps of the seismic rehabilitation process are described. First, the target objective of the seismic rehabilitation and the choice of isolation system type and location are discussed. The design of the isolation system, carried out following a direct displacement-based approach, is then examined. Finally, the main phases followed in the installation of the isolation system are described. Some comments on costs and time needed to complete the intervention are also reported.

Performance evaluation of natural rubber seismic isolators as a retrofit measure for typical multi-span concrete bridges in eastern Canada

More than 46% of the 2672 multiple-span bridges in the Province of Quebec (Canada) are concrete girder bridges. Due to the advanced age and the lack of seismic detailing, these bridges may be vulnerable to earthquake events. In an effort to prevent an interruption of the transportation network, which could be catastrophic for Quebec, a comprehensive research program was conducted whose aims were to assess the seismic vulnerability of typical bridge classes retrofitted with natural rubber seismic isolator devices through the development of fragility curves. The understanding of the impact of various modeling parameters on structural-component responses is the first step in a forward-vulnerability assessment of bridges in Quebec. This paper presents part of a comparative study using detailed three-dimensional nonlinear models that was conducted to assess the longitudinal and transverse responses of multi-span continuous (MSC) and multi-span simply supported (MSSS) concrete bridges in their as-built and retrofitted configurations using different synthetic ground motions (SGM) for the eastern part of Canada. Deterministic responses in terms of column curvature demand, abutment footing deformations, and abutment wall deformations are provided for the longitudinal and transverse directions of bridge models. The influences of various modeling parameters were assessed using analysis of variance (ANOVA) and design-of-experiments (DOE) principles to perform screening of 12 structural parameters. This study revealed that the most important modeling parameters that affect critical components responses of MSC and MSSS bridges are the isolator effective stiffness, the abutment stiffness, and the gap between abutment and deck, in addition to the variation in gross bridge geometry and ground-motion contents. This screening study also gives an indication that the variation in other modeling parameters such as structural damping and skew angle affect the seismic response of MSC and MSSS bridges and should be considered carefully in a seismic-vulnerability assessment for these portfolios of concrete bridges. In addition, it was found that the use of seismic isolation devices effectively reduces the curvature demand placed on columns but has a negative impact on the deformation demand placed on abutment walls.

Seismic Isolation for Advanced Fast Reactors

We present the results of a survey of the state of seismic isolation technology. The emphasis of the review is placed in the United States. The purpose of this survey was to provide an engineering basis for the use of seismic isolation in the design of nuclear power plants. In particular, the survey is focused on providing a basis for the design of advanced fast reactor (AFR) nuclear power plants. These AFR plants typically have components and piping that are thin walled as opposed to the thick-walled components and piping in light water reactor (LWR) plants. As a result the AFR plants do not have the adequate inherent strength to resist seismic loads that exists in the LWR plants. It is far more desirable, therefore, to reduce the seismic demand on the AFR plants than to require costly measures to strengthen the structures and components. It is believed that the use of seismic isolation is a viable and effective way to provide this reduction in seismic demand. Various types of seismic isolation systems and devices are reviewed along with their strengths and weaknesses. Descriptions of several U.S. seismically isolated buildings are presented. The results of actual performance of seismically isolated buildings are also presented, including representative measurements of accelerations in the structures when subjected to actual seismic events. It is concluded that the seismic isolation technology is well established and that the path forward leading to the use of this technology for AFR nuclear power plants is clear and achievable.

Seismic performance of isolated curved steel viaducts under level II earthquakes

This paper investigates the effectiveness of the use of seismic isolation devices on the overall 3D seismic response of curved highway viaducts with an emphasis on expansion joints. Furthermore, an evaluation of the effectiveness of the use of cable restrainers is presented. For this purpose, the bridge seismic performance has been evaluated on four different radii of curvature, considering two cases: restrained and unrestrained curved viaducts. Depending on the radius of curvature, three-dimensional non-linear dynamic analysis shows the vulnerability of curved viaducts to pounding and deck unseating damage. In this study, the efficiency of using LRB supports combined with cable restrainers on curved viaducts is demonstrated, not only by reducing in all cases the possible damage, but also by providing a similar behavior in the viaducts despite of curvature radius.

Experimental Response of Buildings Designed with Metallic Structural Fuses. II

In a companion paper, an alternative design approach was proposed to concentrate damage on disposable and easy to repair elements i.e., structural fuses, while the main structure is designed to remain elastic or with minor inelastic deformations. To verify and validate the developed design procedure, an experimental project was conducted on the shaking table at the University at Buffalo, which consists of a three-story frame designed with buckling-restrained braces BRBs working as metallic fuses. This experimental project also assesses the replaceability of BRBs designed as sacrificeable and easy-to-repair members. These BRBs are connected to the frame by removable and eccentric gusset plate, especially designed to prevent performance problems observed in other experimental research. Design and behavior of this type of connection is also investigated here. Another objective of this test is to examine the use of seismic isolation devices to protect nonstructural components from severe floor vibrations in buildings designed per the fuse concept. The seismic isolation device consists of a bearing with a spherical ball rolling in conical steel plates, also called a ball-in-cone system. This type of seismic isolator was installed on the top floor of the frame model, and its response in terms of acceleration and displacement is investigated as part of this investigation.