Seismic Isolation, Energy Dissipation and Active Vibration Control of Structures

Conventional seismic isolation reduces acceleration and structural damage. However, there is a trade-off between displacement and acceleration. Thus, seismically isolated layer may pound against moat walls when a large earthquake occurs. To address the above problem, we developed a displacement control system (DCS) in previous study. DCS is a seismically isolation system with quasi-zero stiffness (QZS) and rotational inertia. A QZS device is used to improve the control performance of seismically isolation system. However, if the dominant frequency of the input wave varies from low to high, a seismically isolation system with a QZS device causes nonlinear resonance and drastically degrades in control performance. Rotational inertia, however, elongates the natural period and prevents the nonlinear resonance caused by QZS. This study evaluated the steady-state response of our DCS subjected to harmonic excitation through analysis and shaking table tests. The response of DCS to seismic excitation was also investigated through shaking table tests. Comparing the analytical solutions and the test results showed that the analytical solutions agree well with the test results in terms of the frequency-amplitude relationship. The test results of seismic wave excitation indicate that our DCS suppresses the maximum response displacement within the seismic gap.

Seismic events like the Fukushima 2011 and the recent disaster caused by the Maras doublet on 6 February 2023 highlighted the weaknesses of conventional construction methods and seismic protection systems under extreme conditions. Despite the existence of advanced safety measures and regulations, there is still a need for research and development of robust and innovative methods to enhance resilience against both natural hazards and human factors during construction and operation, while also satisfying the sustainability and efficiency requirements. Metamaterials and metastructures, which are nowadays carefully designed by engineers to exhibit specific properties to control wave propagation, have emerged as a promising area of research for seismic protection. Among various examples, metafoundations (MFs) based on locally resonant metamaterials have shown great potential as a simple and effective solution while also being beneficial for standardizing the design of critical infrastructure, industrial and nuclear power plants, and their components. The purpose of this study is to present the advantages and limitations of MFs and provide knowledge for future developments. Compared to traditional approaches, MFs offer multidirectional and adaptable seismic protection owing to their modular construction. Firstly, the study discusses the parameters that affect the performance of MFs and their correlation with each other, highlighting the design flexibility of MFs. Specifically, the adaptability of MFs was explored concerning reducing risk and allowing a single superstructure design to be used in different locations with varying demands and requirements, enabling the design standardization for the superstructure. The standardization aims to use the same -optimized, simplified and precisely studied- design of the superstructure to be constructed many times, which in return, reduces construction times, minimizes human error or influence during the construction stage, and enhances efficiency and sustainability. Additionally, special attention was paid to a novel mechanism of inerters to improve the performance and/or reduce the dimension of MFs. Finally, it was shown that the MFs with multiple layers can be more robust against the mistuning of resonators.

To ensure best seismic protection of structures for various seismic conditions, base isolators need to perform according to specific seismic requirements. These base isolators are commonly designed mainly for the MCE level. By doing so their efficiencies are poor with regards to soft breakaway at DBE, which means that due to static friction significant acceleration may be transferred to the superstructure already before the first isolator displacements occur. These systems are even locked-up. This shortcoming can only be improved if the friction within the devices is not constant at different yield levels. This approach allows generating the same structural isolation system for the MCE as conventional devices but significantly improves structural performance for breakaway and for low to medium seismicity. The isolation performance of a new adaptive curved surface slider is explained in terms of absolute structural acceleration and device´s displacements, computed as function of the ground shaking level and compared to the conventional devices. Additionally a reference of Zubiran Hospital in Mexico will be presented.

Elastoplastic dampers (EPD) have found a wide application all over the world as standalone seismic restraints or elements of structural seismic isolation systems. This paper proposes a series of methodologies for determining the key parameters of the elastoplastic dampers, which involve the actuation force, force diagram, and the number of operating cycles. These methods build on the laws governing the variation of resistance forces in an EPD, the former being intricately dependent on plastic elements’ previous exposure to stress, as well as on the properties of steels they are made of. The paper further discusses the rigid-plastic and elastoplastic analyses, the pseudorigidity method algorithm, and the macromodel method, presenting analytical dependencies for simplest damper designs, as well as analytical and semi-analytical dependencies for the general-independent force curves of rectilinear element with rectangular cross-section, quarter-circle element, hardened elastoplastic material, and samples with circular cross-section. Examples are provided of the application of the proposed techniques, as well of experimental studies into the mechanical properties of elastoplastic elements. The proposed methods allow for a more comprehensive approach to calculating the design of the elastoplastic dampers for use in seismic protection systems.

The purpose of this study was to investigate the combined use of two different types of isolators and their benefits when used together in buildings. A building model was constructed incorporating both Lead Rubber Bearing (LRB) and Elastic Slider Bearing (ESB) isolator types within the scope of the study. To generate earthquake acceleration records for structural analysis, specific soil parameters were selected from a defined region. The earthquake acceleration records were then fitted to the horizontal elastic design spectrum using Mathworks Matlab software. Finally, analyses were performed using the CSI ETABS structural analysis program. Given the absence of a re-centering feature in the elastic slider bearing, it is anticipated that its use alongside a lead rubber isolator would provide more favourable results. The analysis results indicated that the use of these isolator types together gave positive results, particularly in scenarios where the structures were subject to high axial loads and a longer construction period was desired.

The response of bae-isolated structures is affected by the variability of dynamic properties of isolation bearings due to environmental effects, such as the temperature and ageing, and/or behavioral effects. For elastomeric bearings made by High Damping Rubber (HDR), the main behavioral effects are the strain amplitude and the strain rate dependence of the shear response and the load history dependence. They can be all included in advanced numerical models, alternatively current seismic codes allow to adopt less accurate models in combination with property modification factors (also called λ-factors) defined for both behavioral and environmental effects.These factors should be experimentally assessed during the qualification process of bearings but, in some cases such as in the European context, the product standard on anti-seismic devices (EN 15129) allows the manufacturers to deduce these variabilities from tests performed on material specimens. In this paper a statistical analysis is carried out on a large set of material tests carried out according to EN 15129 on low and high damping rubber compounds provided from different suppliers. Based on the results, new λ-factors for stiffness and damping are proposed and compared with those deduced from the “λ-factors” suggested in the informative annexes of EN 15129 and EC8-part 2. In the last part of the paper some preliminary considerations are made on the influence of such variability on the vulnerability assessment of base-isolation structures.

There are various designs of seismic isolation of buildings and structures, in the foundations of which spherical surfaces with rolling balls, rubber-metal layered seismic isolators, as well as complex metal spring seismic isolators are used. The goal was to create such a seismic isolation foundation, which would simultaneously combine all the advantages of the above seismic isolators. There are various designs of seismic isolation of buildings and structures, in the foundations of which spherical surfaces with rolling balls, rubber-metal layered seismic isolators, as well as complex metal spring seismic isolators are used. The goal was to create such a seismic isolation foundation, which would simultaneously combine all the advantages of the above seismic isolators. A new seismic isolation foundation of the building has been developed, which includes the upper and lower supporting parts, in which cylinder sleeves with inclined bottoms are formed, an intermediate element in the form of a ball and an elastic insert. The elastic insert is located on the bottoms of the upper and lower cylinder sleeves, and on the surface of the bottom of the sleeve and each insert, a steel Belleville spring 5 mm thick is located and fastened to them. In each cup, the elastic liner forms a complex non-linear surface around the intermediate element, which in the section forms ascending halves of a sinusoid, which is a companion of the cycloid built in a circle with a diameter equal to half the diameter of the intermediate element. In this case, there is a gap of 10 mm between the end surfaces of the walls of sleeves.

Swelling clay soils are often located in seismic hazardous areas. It increases the risk of emergency moistening of a clay base. Using pile foundations for structures in the case of clay soils swelling causes the affect of negative friction forces. It contributes to the uneven vertical thrust of piles. For seismic isolation of pile structures, it’s necessary to develop protective measures requiring additional costs. Innovative designs of driven and filling piles were developed for swelling clay soils provided with elastic screens. In the case of using driven piles, tubular elements were used, made from a pack of the same type of old metal cord tires, in the internal holes of which special cutouts were made equal to the cross-sectional parameters of the driven pile. In the case of using filling reinforced concrete piles, the holes were first made corresponding to the outer diameter of old tires. On the inside, between the edges of old tires and the side surface of the filling pile shaft, there’s a polymer film preventing liquid concrete penetration into the cavities of recycled tires. The screens absorb the pressure and deformation of swelling clay soils, and also serve as seismic isolation during strong earthquakes. The proposed designs of piles for swelling clay soils are considered relatively cost-effective ones, as they are prepared on the basis of waste.

The importance of improving the surveillance and maintenance of road infrastructures has become an issue in most countries in the world. Actually, most bridges were built several years ago, when traffic loads were different from the current ones and seismic actions were often neglected. Today, one of the main goals is the identification of suitable seismic retrofit interventions for existing bridges. A scaled span of a real viaduct was tested on a shake table in order to study the efficiency of different isolation systems, composed of HDRBs and SDs or CSSs, in comparison with the original rubber support systems. Different sensors were used to measure accelerations and displacements of the structure under increasing seismic input and to point out the different experimental behavior of the seismically isolated configurations. HDRBs + SDs allowed to obtain significant reduction in accelerations and no residual displacements, while the performances of CSSs were improved by means of lubrication.

Limited by the capability of testing machine, the experimental results of large tonnage friction pendulum bearing under ultimate states are insufficient, such as performances under twice of the design compressive stress or under high-speed shearing rate, etc. Therefore, to ensure adequate safety margin, the limited design axial force is always low. And the high-speed shearing performances of the friction pendulum bearing rely on theoretical analysis only due to lack of actual test results as evidence. In order to demonstrate the ultimate state performances of the large tonnage friction pendulum bearing, a 40 MN design capacity’s friction pendulum bearing was performed on the 100 MN compression-shearing testing machine at Guangzhou University, which is the maximum testing machine in China. The compression performances are tested under 40 MN (design force) and 80 MN (double design force) as vertical force. The compression curves are regular and no any cracks or damages observed after testing. The horizontal performances are tested at 150 mm/s, 500 mm/s and 1000 mm/s as shearing speed, all the hysteresis curves were full and no any damages observed. These test results under ultimate states provide sufficient confidence for the engineering application.

“E-Isolation” has developed and adopted a new system that can directly measure the reaction force of the devices, excluding of the friction force generated in the bearing under the moving platen and the inertial force due to the weight of the moving platen. In this paper, three tests were conducted to verify the accuracy of the measurement system in “E-Isolation”: (1) a verification test of the horizontal stiffness of the reaction beam supported by laminated rubber bearings, (2) a static test that horizontal load of 1000 kN was applied to the reaction beam and the moving platen, and (3) a performance test using a natural rubber bearing with a diameter of ∅1200. Test (1) showed that the horizontal stiffness of the reaction beam system can be accurately evaluated based on structural performances of the supporting bearings, and that the maximum horizontal load acting on the reaction beam support is extremely small. From the results of (2) and (3), the system demonstrated a possibility to directly measure the reaction force of the specimen without effects of friction and inertial forces. In addition, it has been confirmed that the reaction measurement links and the rotation constrain links bear the horizontal loads in the ratio of 3:1, as assumed in design at the horizontal load.

The full-scale dynamic seismic isolation testing facility (E-Isolation) newly constructed in March 2023 at Hyogo prefecture, Japan. This testing facility employs a system that is possible to conduct experiments on full-scale specimens that subject them to large deformations dynamically. In this paper, the analysis is based on natural rubber bearings with a wide range of comparative studies ranging from 300 mm to 1200 mm rubber diameter. In conducting the experiments, the reduced-scale specimens with 300 mm diameter and the full-scale specimens with 650 mm diameter are tested using a two-stage loading apparatus, and the full-scale specimens with 800 mm and 1200 mm diameter are subjected to horizontal loading experiments in E-Isolation. It was found that natural rubber bearings show highly linear structural behavior including extremely small amplitude region of less than 10% shear strain and dependence of compressive stress, deformation amplitude and frequency on horizontal stiffness in reduced-scale to full-scale specimens.

Rolling isolation systems using elastomeric spheres may provide significant advantages over traditional methods (i.e., rubber bearings or frictional pendulum systems) in terms of cost-efficiency. The concept involves placing elastomeric spheres between the foundation and the superstructure. The spheres can roll and rotate in response to seismic activity, either on a concave surface or a flat one with additional restitutive elements. Energy dissipation is provided through the rolling resistance, which is due to the continuous deformation of the elastomeric material. This paper analyzes the system behavior regarding its force-displacement relationship and the deformation of the sphere material through finite element modeling and experimental tests. The results show that the creep of the ball due to the weight of the structure negatively affects the system behavior because the sphere becomes oblong. Finite element models show that it is the material closer to the inner part of the ball that mostly contributes to the final oblong shape, while the material closer to the surface contributes to energy dissipation. This shows that the oblong shape can be reduced by placing an inner steel core in the sphere (since the inner part of the ball is no longer deformed) without compromising the energy dissipation. Recent experimental tests on grout-filled tennis balls validated this behavior. Overall, the rolling isolation system using elastomeric spheres with an inner steel core could represent a robust and reliable alternative to protect structures.

In seismically isolated buildings, expansion joints are installed in floors and ceilings to absorb the relative displacement between surround grounds and the seismic isolated buildings, ensuring safety and functional maintenance after earthquakes. In this study, collision experiments were conducted to determine the magnitude of the horizontal impact force generated by the collision of the main panel to a sloping section on the exterior structures. As the test results, it was clarified that the horizontal impact force was affected by the angle of the sloping section, the collision velocity, and the total mass of the main panel. The horizontal impact force increases in proportion to the collision velocity and the effective mass of the main panel, respectively. However, the effective mass on the horizontal impact force was dominated by the forward side of the main panel, influenced by the position of the additional weight. Also when the angle of the sloping section was reduced from the 45° to 30°, the horizontal impact force was roughly halved. On the other hand, when the angle was increased from 45° to 60°, the horizontal impact force was roughly doubled. Generally, 45° is used for the angle of the sloping section, however architects prefer a larger angle because it allows the expansion joint to be more compact. Based on the test results, it is recommended that employing a smaller angle for the sloping section is preferable from the point of protecting the exterior structure. For structural engineers, an evaluating method of the horizontal impact force for designing the exterior structure has been proposed.

Based on existing specifications, the mechanical parameters of rubber bearings are primarily derived from the third hysteresis curve of its compression-shear test. However, when subjected to near-fault velocity pulse ground motion, the isolated structure will experience a greater concentration of energy input over a shorter period of ground motion, whereas the rubber bearing of the isolation layer typically only experiences one or two cycles of large horizontal deformation, which may lead to a significant departure from the desired outcomes when applying the mechanical parameters obtained from the third circle for the building’s seismic responses. In this paper, high-speed compression-shear apparatus is used to conduct a series of compression-shear tests at varying frequencies (0.20 Hz, 0.25 Hz, 0.30 Hz), and shear strains (50%, 100%, 250%) on rubber bearings. The mechanical properties corresponding to the first and third hysteresis curves of the laminated natural rubber bearings (LNR700) and lead rubber bearings (LRB700) are extracted and compared. In the third circle, an increase in the amplitude of shear strain results in a corresponding increase in the rates of change of the characteristic strength, horizontal equivalent stiffness, and equivalent damping ratio of the isolation rubber bearing. Under 250% shear strain, the characteristic strength, horizontal equivalent stiffness, equivalent damping ratio of LRB700 decrease by 34%, 15%, and 33%, respectively, compared to the first circle, while the horizontal post-yield stiffness of LRB700 and the horizontal equivalent stiffness of LNR700 remain essentially unchanged. Therefore, in the design of building isolation, the risk of increasing seismic response of the superstructure due to the increase of bearing characteristic strength and horizontal equivalent stiffness caused by instantaneous pulse ground motion must be taken into account.

The pile-top seismic isolation method simplifies the foundation structure under the seismic isolation layer by installing the isolators directly on the top of the piles and contributes to cost reduction. However, the rotation deformation constraint effect of the pile-top method is smaller than that of the conventional seismically isolation applications with a relatively stiff foundation layer. As a result, the seismic isolation devices also rotate and deform as the pile-top rotates. In this study, cyclic bi-axial loading tests on special elastic sliding bearings with rotational deformation capacity were carried out, which can be implemented in the pile-top seismic isolation method. The tests were carried out to confirm the basic performance and dependence on the rotational deformation angle of the devices. According to the tests, it was shown that the friction coefficient was not affected up to the rotational deformation angle of 1/100 radians of the elastic sliding bearings. In addition, during long-period and long-duration ground motions, the response deformation may become excessive due to the change in the performance of the elastic sliding bearing. In order to confirm the performance of this elastic sliding bearing under long-period and long-duration ground motions, additional cyclic bi-axial loading tests and thermal-mechanical coupled analysis were conducted. It was observed that the friction coefficient decreases with the rising temperature of the sliding plate, and the performance of the device under long-period and long-duration ground motion was confirmed.

The theoretical behavior and modeling of seismic isolation devices are based on the evaluation of experimental tests results. Base isolation devices’ manufacturers can estimate the behavior and performance of their products depending on these evaluations. Experimental tests may be either small-scale material or model tests, or full-scale dynamic prototype tests. This report focuses on the evaluation of more than 25000 test data from full-scale dynamic prototype and small-scale quasi-static material tests. The test data is obtained from the database of TIS Technologic Isolation Systems (TIS). The data includes the results of dynamic tests performed on more than 300 double surface friction pendulum prototypes (curved surface sliders), and small-scale quasi-static material tests applied on TIS’ special sliding material. The behavior of friction pendulum devices mainly depends on the frictional characteristics of sliding surfaces. Hence, it is essential to categorize and quantify the factors that affect their friction behavior. The test data evaluated and presented in this report considers a vertical load in the range 100–60000 kN, environmental temperatures ranging between 6 and 34 ℃, sliding velocities in the range 0.1–1500 mm/sec, displacements up to ± 1000 mm, and oscillation periods between 2.55–5.92 s for a large variety of double surface friction pendulum devices. This database is being assessed to evaluate the impact of different parameters on the performance of friction pendulum type base isolation devices in a more sophisticated manner.

Artistic assets are highly vulnerable to natural hazards. Past earthquakes have caused worldwide enormous losses due to either extensive damage or collapse of artefacts. Thus, there is an urgent need to protect efficiently artistic assets in earthquake prone regions. Seismic base isolation is a mature technique that can provide a viable solution for such assets. However, the performance of existing seismic isolation devices, e.g. pendulum devices, is not sufficiently investigated, both experimentally and numerically. Statues, busts, pedestals and museum displays are typically lightweight elements, thus the relatively low weight can affect the friction response of pendulum devices. The present paper illustrates the outcomes of a comprehensive experimental test programme aimed to investigate the seismic response of museum contents and develop risk mitigation strategies to improve their seismic resilience. Several layouts and different earthquake scenarios were considered for the shake-table tests carried out at CEA laboratory, Saclay, France on free-standing full scale pedestals and busts. The outcomes of the experimental tests discussed hereafter demonstrate the efficiency of pendulum devices and highlight the presence of amplification in the response of multiple block assemblages comprising pedestal and busts, for relatively low-values of accelerations. Additional studies should be carried out to investigate whether the modes of vibration of the unanchored multiple blocks on base isolation systems are beneficial for the global response of the art objects, including pedestals and busts/statues.

This study illustrates the comparison between the experimental testing of a two-storey braced-frame structure semically protected by means of and isolation system and the simulation of such tests. More in detail, the steel structure rests on a reinforced concrete slab isolated from the foundations through a hybrid system consisting of 28 High-damping Rubber Bearings (HDRBs) and 36 low-friction sliders (LFSs). During the building design the removable push-and-release device, the reaction wall, and the pushing point were also designed to minimize the cost of the tests and to allow repeated testing throughout the service life of the building. The global dynamic response was tested up to displacement amplitudes similar to those induced by extreme seismic events. In particular, maximum horizontal displacements of 285 mm and 227 mm in the quasi-static and dynamic tests are reached respectively. Conseqeuntly, the test can be de-facto considered as an in-situ verification of the seismic behaviour of the isolation system. However, in the case case of elastomeric bearings this testing procedure is not properly equivalent to an earthquake excitation, mainly due to the different deformation velocities and the not negligible viscous effects of HDRBs. Therefore, this work aims at understanding and evaluating the observed experimental behaviour by assessing and calibrating a model able to simulate all the the viscous effects and the energy dissipated by the sliders. This way, the viscous displacement accumulated during the loading phase, causing the system to oscillate around a non zero displacement during the release phase, can be simulated.

The February 6, 2023 Magnitude 7.8–7.5 earthquake in Turkey has shown and confirm an efficiency of seismic isolation for protection of buildings and structures against seismic motion. However, there is no enough information regarding behavior of the seismic isolated structures and hospitals subjected to the peak ground acceleration over 0.5 g. At the same time recent investigations during Tohoku Earthquake 2011 and at the world’s biggest E-Defence 1500 tons shaking table in Japan have demonstrated inconsistent results for conventional isolation systems with an essential seismic amplification in the vertical direction and limited overall efficiency. This contribution presents results of analysis, natural scale testing and application cases of the passive Base Control System (BCS) consists of the spatial (3D) coil spring isolators and separately located 3D viscodampers. According to the performed investigations the BCS is able to provide an optimal stiffness, frequencies and damping close to the optimal values for the current site seismic data and structure’s features in the range of 0.5–2.0 Hz in the horizontal direction and 1.5–3.0 Hz in the vertical direction with system’s damping over 20%. The efficiency of the BCS system were confirmed by natural scale testing at the unique 3 000 metric tons test rig. A comparative analytical study has confirmed an advantage of the BCS system against other isolation systems providing isolation efficiency in all directions of structures’ seismic response.

This paper reviews the 40-year history of seismically isolated buildings in Japan and discusses the challenges in the development and dissemination of the technology. Although seismic isolation has shown excellent performance in past earthquakes, there are still many problems, such as damage to expansion joints and other nonstructural components. In addition, although there are many examples of high-rise seismically isolated buildings in Japan, there are few examples worldwide. Because seismic isolation requires high-level knowledge and technology in design, construction, and maintenance, the development of technical guidelines is essential for its widespread use. Finally, international standards (ISO 23618) for seismic isolation design are introduced.

The response of an isolation system made of HDRBs and SDs under low energy earthquakes, classified on the basis of the energy at the basement, is analyzed. The study pointed out that for very low values of the energy, measured by means of the Arias intensity, the isolation system was not put in action, and the superstucture behaved like a fixed base one. The behaviour has been correlated to the ratio between the inertial force resultant and the maximum friction forces of the slider devices. For higher values of the energy, instead, the isolation system was activated and a value of the Arias intensity was individualized, which separates the two behaviours. The variability of the first resonance frequencies with the input energy has been particularly analyzed, as well as the structural response in terms of maximum accelerations, maximum displacements and relative horizontal displacements in the building.

The machine learning-based hybrid seismic analysis developed recently by the authors is validated in this paper using the full-scale experimental data of a shake-table test program performed at the Hyogo Engineering Research Center (E-Defense) of Miki, Japan. The experimental datasets contain the time history responses of two base-isolated buildings, each with the lead rubber bearings (LRB) and the triple pendulum bearings (TPB). First, the machine learning models (MLMs) based on the recurrent neural network (RNN) are designed to predict the complex load-deformation relationship of seismic isolators at the isolation layer. The experimental data are used to train and test the surrogate MLMs. Then, the developed MLMs are incorporated into the time integration method to perform the hybrid seismic analyses of base-isolated buildings subjected to the earthquake ground motions. The hysteresis curves of the isolation layer and the roof displacement time-histories are calculated and compared with the experimental records. The hybrid seismic analysis could capture the experimental responses. The proposed hybrid seismic analysis that takes advantage of both analytical methods and machine learning-based methods was found to be capable of obtaining with good accuracy responses of seismically isolated buildings.

Eleven provinces along the East Anatolian fault line have been severly affected from the Pazarcık M7.7 and Elbistan M7.6 earthquakes which occured in Kahramanmaraş, Türkiye on February 6, 2023. Many buildings in these provinces were totally collapsed. However, it is observed that several buildings located in the vicinity of the collapsed buildings which received adequate engineering services either sustained controlled damage or did not receive any damage at all in accordance with their design target. It is clearly observed that bearing soil conditions have a significant effect on the level of damage to buildings during these earthquakes. Most of the buildings that were destroyed or severely damaged during these earthquakes were built on very weak soil such as alluvium. However, it is another fact that the centers of the cities were located on soft soil near rivers or plains having agricultural value. In this case, it is clear that the first attempt to be made is to reconstruct the cities where they used to be. It is also of great importance that the city center of Antakya, which is known to have an important value in terms of the Middle East history and the history of religions is included in the UNESCO World Heritage List. Hence, the city has to be reconstructed in the place where it is used to be. Considering the importance of the methods to be developed using high technology to increase the earthquake performance for the construction of the city center, a pilot study is conducted by choosing an existing zone with 9 apartment blocks at the city center. For this purpose, a block in Antakya General Şükrü Kanatlı Quarter with 9 buildings consisting of 5 and 8 floors is chosen as the pilot project region. A method has been developed to reconstruct these 9 structures in the region with seismic isolation. The foundation, insulator and plinth floors of the pilot region are designed as a single monolithic base and separate residential blocks placed on it. Basement floor consists of parking lots and shops. This study offers an economical solution that is safe against earthquakes, solves the parking problem of the blocks, and enables using infrastructure services of the central region of the city by preserving the current location and silhouette of the region, seismically protected with advanced technology.

When subjected to earthquakes some elements or structures behave like rocking rigid bodies. Art objects, computer servers and electrical equipment are frequently included in this category. This study is motivated by the need to protect these non-structural elements from earthquakes and base isolation technology was proven to be a viable option for this purpose.The dynamic model of a rocking rigid block placed on a base isolation device is summarized here. Then, a rotation-based procedure to design this type of protection system for rigid rocking bodies is proposed, and the main steps are illustrated. The procedure is aimed at designing base isolation devices for rocking bodies, in order to activate a specified maximum rotation during the code-level earthquake event.The presented rotation-based procedure is particularly suitable for large structure / objects, as long as small oscillations are acceptable. Indeed, as the block size increases, the capacity of the system also increases. The main advantage of this procedure is that the maximum displacement of the isolator can be reduced compared to the case where rotations are not allowed, hence rocking motion is not initiated. Despite this advantage, the design procedure allows the rigid body to rock and, thus, to impact the base.

In the aftermath of the earthquake in Turkiye, it was visible that seismically isolated buildings behaved excellently, just as expected. Japan’s extensive use of seismic isolation began after the Kobe earthquake, when the few seismic isolated buildings went through the devastating earthquake with no damage.Romania’s last big earthquake was many years ago, and people tend to forget about the great disaster that was produced in 1977. However, the engineering community is taking steps towards the improvement of our built environment. Although until recently, seismic isolation was only used for retrofitting works on public buildings, private residential buildings started being built with the base isolation.The construction method is not new, and design companies started adopting it because its advantages are obvious, so owners started not choosing only the traditional way because of economic reasons but also adopting new technology to protect the functionality of the building after a strong seismic event. Romania is one of the most seismic-prone countries in Europe, after all.In this paper, several recently constructed buildings are presented. These buildings are all private and equipped with seismic isolation interfaces allowing the owners to adopt bold shapes of the structure.

In October 2022, “ISO 23618:2022 Bases for design of structures - General principles for seismically isolated structures” was published. A Technical Report based on ISO 23618:2022 is prepared to demonstrate how to use the ISO standard. In this paper, a seismically isolated building design example using response history analysis method based on Japanese code is summarized.In Japan, the same design earthquake ground motions and the same procedure of response history analysis method are applied to all structure types such as aseismic, seismically isolated or energy dissipation structure. There are four types of ground motions to be considered in the response history analysis. The maximum response values from the above ground motions are used to design. The design shall be conducted on both Level 1 (damage limit) and Level 2 (safety limit) earthquakes. To check the vertical response of isolators, vertical motions pairing with the horizontal one are usually used. Both the equivalent linearization method and the response history analysis method may be used for a seismically isolated building. However, 80% of the projects adopted the response history analysis method for the performance-based design or economic reasons.For the building model, a multiple-degree-of-freedom lumped mass model or/and a 3D frame model may be used. 70% projects were reported to adopt the lumped mass model due to the physical understanding of the response. Members of the super-structure are assumed as non-linear. Isolators and dampers are modelled appropriately based on test results. A seven-story RC education building will be used to demonstrate the design process in detail.

Normal isolator movement requires a wide isolation groove between adjacent base-isolated high-rise buildings, which is wasteful in terms of urban space. To solve this problem in China, large podiums are used in base-isolated multi-tower high-rise buildings. However, implementing the design procedure involves numerous difficulties. The podium needs to resist compression and shear forces due to significant differences in the dynamic characteristics of different towers. Other challenges include detailing the layout of the isolation system, selecting isolators to meet performance targets, analyzing the floor stress, and analyzing the temperature. The innovative base-isolation design procedures of multi-tower high-rise buildings with large podiums in highly seismic zones are validated. An ongoing project in Yunnan province, China, is taken as a case study, and the patented, high-performance rubber bearings for reducing the seismic response is used in this project, its effectiveness is verified through a series of experiments. This paper has guiding significance for similar engineering projects.

The paper is focused on the recent trend of using fluid viscous dampers in seismic isolation system of hospitals or other strategic buildings. The effectiveness of high energy dissipation capacity of the seismic isolation system in reducing its displacement is well known. However, a high hysteretic/bilinear energy dissipation can increase the higher-mode response, and consequently is not optimal in strategic buildings. Conversely, energy dissipation provided by viscous dampers guarantees the best response both in the first modes and in higher modes. Furthermore, energy dissipation dependent on velocity guarantees the activation of the seismic isolation system at any level of earthquake. Some hospitals case studies are described, with fluid viscous dampers combined either with pendulum isolators or with elastomeric isolators. Some full scale test results on devices used in said hospitals are reported as well.

An overview of the most used seismic isolation systems implemented in the Republic of Kazakhstan is offered. These are kinematic foundations, special elements with dry friction, newly developed systems based on planar robots, a system based on a ringless frame on kinematic foundations, classical pendulum systems based on dry friction elements, as well as promising systems using rubber-metal supports and supports made of rubber blocks. In the city of Almaty with the use of such foundations, over 40 houses with a height of 2–16 floors (brick, large-panel, frame-brick) were built. The system based on a frame on kinematic foundations with magnetic dampers was implemented during the construction of 3-storey cottages in the suburbs of Shymkent. As an active seismic isolation system, the use of a platform robot is proposed. This combination is very promising, as it allows you to perform detuning from the frequency characteristics of the seismic impact. As a scientific facility in Almaty, there is a seismic isolation polygon consisting of three nine-storey large-panel buildings differing in the design of the foundations. A building with a conventional ribbon foundation, a building with a seismic-isolating kinematic foundation and a building with fluoroplastic gaskets were built. All buildings are equipped with sensors, which in real time allow you to get information about the reaction during earthquakes of varying intensity. Currently, it is planned to build buildings of schools and hospitals in the city of Almaty only with the use of seismic isolation systems.

Building collapses due to recent severe earthquakes have activated searching for effective seismic protection systems. A comparative study of the most popular systems has been performed using numerical model of the well-known test building experimentally investigated at the world’s biggest E-Defense shaking table in Japan. In the presented study the calculation models for the following seismic isolation systems were prepared: a) a model for rigid supported building; b) a model with triple pendulum bearings (TPB); c) a model with rubber bearings (RB) combined with viscous dampers (VD); d) a model with the Base Control System (BCS) consisting of coil springs and viscous dampers; e) a model with kinematic supports (KS) often used in Russia. The models a) and b) were validated using test results. Models were prepared considering most of the nonlinear effects in the isolation devices. The calculation results show good effectiveness of TPB, RB and BSC systems in reduction of seismic horizontal accelerations. At the same time, the addition of seismic ground motion in vertical direction significantly increases the building horizontal acceleration response in case of TPB and RB systems, i.e. the strong 3D interaction between horizontal and vertical motion was presented. For these systems amplification of high frequency vertical motion was also observed. In the case of BCS, the calculated 3D interaction was much less compared to other systems and there was no vertical response amplification. KS failed under the test conditions which required using of additional motion restriction devices in the KS design. Conclusions: simple realistic models for different isolation systems have been proposed. TPB, RB-VD have good performance, BCS has been selected as the most preferable system.

In this report, we experimentally examine the stopper design and structural response estimation that were established for a free-standing structure to suppress its residual sliding displacement without impairing the high performance of seismic damage mitigation. For this examination, we conducted a series of shake table experiments on a free-standing single-storey structure based on the graphite-lubricated sliding interface whose friction coefficient is about 0.2, as well as a conventional structure fixed to the ground. The conventional structure suffered severe structural damage due to the yielding of its structural components when excited by excitations with intensities of Lv 2, corresponding to a major earthquake in Japan, and its 1.4-fold. Contrarily, the free-standing structure did not suffer such damage under the same excitations, because of the base isolation effect of sliding. However, it had large residual sliding displacement (over 100 mm) after each excitation. Under the same excitations, the free-standing structure with cushion stoppers, which was made by following the stopper design, effectively restrained the residual sliding displacement around 10 mm, without losing the high preformation of seismic damage mitigation. In these experiments, the shear coefficients provided by the structural response estimation were sufficiently close to the actual values of the superstructures in the free-standing structures. This study clarified the effectiveness of the stopper design and structural response estimation in reducing the residual sliding displacement and maintaining the high performance of structural damage mitigation.

Fragility functions provide important tools to the designer for reliable dynamic performance assessment of structures, considering the effects of uncertainty in the earthquake excitations. Given the catastrophic impact of the recent earthquakes on society, it is of prime importance to maintain operational condition in hospitals during earthquakes, for effective disaster management. Therefore, the present study demonstrates the advantages of base isolation of lifeline structures, such as hospitals, in ensuring continued functionality of the structure during and after earthquakes. An existing irregular-shaped hospital building in Avezzano (L’Aquila, Italy) is considered for evaluation of its seismic performance. The efficacy of three different base isolation systems (BISs), namely, high damping rubber bearings (HDRBs), lead rubber bearings (LRBs), and friction pendulum systems (FPSs), are investigated in the vibration control of the considered hospital building, when subjected to site-specific bidirectional earthquake excitations. Nonlinear dynamic analyses are conducted on the 3-dimensional model of the base-isolated hospital buildings to evaluate its seismic response. Further, fragility curves of the various uncontrolled and base-isolated structures are developed based on the limit state of maximum acceleration response corresponding to (a) tolerance level of the building occupants and (b) slight damage of the nonstructural equipment. Results show that the performance of the HDRB-isolated structure is supreme, followed by the LRB-isolated structures, and subsequently the FPS-isolated structures, under the given scenario. Nevertheless, all the BISs could effectively reduce the structural responses of the irregular-shaped hospital building under the bidirectional earthquake excitations.

It has become a consensus in most countries that higher seismic fortification goals should be applied for school buildings than that for residential buildings and typical apartments. Newly issued Chinese seismic regulations and specifications require that in the same seismic areas, the goal for school buildings is “normal use after moderate earthquakes”. To realize the goal for school buildings, both of two design schemes: moment-resisting frame using a performance-based seismic design method and isolated structure, can be adopted in theory. However, it is unknown about the efficiency and economy of the two methods in practice. This paper designed school buildings using performance-based seismic design method and vibration isolation design method. The response spectrum approach and nonlinear time history analysis using ETABS software were conducted. The seismic performance and construction cost were analyzed. The results show that both of the two design methods are effective ways to realize the high design goal. The seismic isolation technology is more effective and economical in high seismic hazard zones for school buildings. The isolation interface extends natural periods of the isolated structure, and reduces both the static and dynamic responses of the superstructure. Additionally, the excavation of the isolation interface can increase the whole construction cost slightly.

A seismically isolated building subject to tsunami loading was simulated using 3D flow model to evaluate the tsunami load. The building is reinforced concrete building whose size is 70 m in width, 35 m in depth and 20 m in height. A pit for isolation layer, whose height is 1.5 m, is modeled beneath the building. The gap between the building and surrounding retaining walls is 0.6 m. Analyses using a model without pit were also conducted to investigate the effect of the presence of isolation layer space. The tsunami flow was provided from the angle of 0, 45, 90 degrees to the face of the building. Inundation depth and Froude number of the flow at the front of the building is about 5 m and 1.2, respectively. Both a dynamic building model that simulates seismic isolation characteristics and a fixed-based building model were used. The results show the following: An isolation layer space provided tsunami load alleviation if the building does not displace to close the gap. When the gap was closed, water alternately escapes from the side gap, which may excite large vibrations in the orthogonal direction. For the seismically isolated building, the buoyancy force reached about half of the total weight of the building. In the case of the diagonal 45-degree input, the shock wave force at the tsunami arrival was not seen, which was observed in the results of X- and Y-directional inputs. The sustained wave force was proportional to the width of building face to the tsunami flow.

This paper proposes a real-complex hybrid modal response spectrum method (RCHM-RSM) for the design of seismically base-isolated structures. In contrast to the complex modal response spectrum method (CM-RSM), the proposed method not only improves the accuracy of the structural response but also avoids complex calculations. It has been observed that the use of conventional methods to construct damping matrices of base-isolated structures may cause a significant reduction in calculation accuracy. Thus, a new approach is proposed for determining damping matrices of base-isolated structures by assembling the damping matrices for substructures. In addition, an iterative analytical procedure is introduced that integrates equivalent linearization with real and complex mode theories. A benchmark base-isolated structure is presented as a numerical example to evaluate the efficacy of the proposed method. The numerical results of the novel method were compared to those obtained from the CM-RSM, forced decoupling response spectrum method (FD-RSM), and nonlinear time history analysis (NTHA). The research results show that the use of the proposed RCHM-RSM can effectively improve the analysis accuracy of the base-isolated structure, which possesses the advantage of high performance, high efficiency, flexible and ease of use. The results also show that the currently used damping models of base-isolated structures may overestimate the damping effect of the structure and thus underestimate the structural response.

Buildings and structure protection against the dangerous effects of earthquakes is one of the priorities set by the government of Russian Federation to engineering community. Seismic isolation systems are actively introduced into the practice of earthquake-proof construction in Russia. This is evidenced by many unique objects using seismic isolation systems. Their design and construction is conducted in the Russian Federation with the participation of specialists from the Research Center of Earthquake Engineering, which is the part of the Research Institute of Building Construction and Russian Association of Earthquake Engineering. After the publication of a new edition of the Russian codes, seismic protection systems have found application in medical, educational, and residential buildings. Standard solutions were developed for seismic protection of structures whose own seismic resistance is lower than the seismicity of the site.

From the past to the present, various solutions have been produced against the earthquake force, which significantly affects the structures. One of these solutions is the use of seismic isolation system. One of the purposes of using seismic isolators is to minimise the acceleration caused by the earthquake force that will affect the structure and the damage that will occur. Seismic isolators work in both vertical and horizontal directions while performing their functions in accordance with this purpose. The vertical load capacity of isolators varies depending on the type of isolator and the diameter of the isolator. One of the criteria used in the selection of isolators in the design of base isolation structures is the axial load value to which the isolator system will be subjected. Particularly in the base isolation solutions of thin and long structures, some isolators may be subjected to tensile forces due to the tip-ping movement that the structure is likely to experience during an earthquake. In this case, although increasing the diameter of the isolator is a solution, this solution is not preferred because it increases the overall cost, negatively affects the architecture of the structure and increases the difficulty of the test phase for this situation. The aim of this study is to mention how the anti-tension device, which can be used as another solution to the extra tensile force, can bring a solution to this situation and to provide information on its application by revealing the advantages of this material. To this end, the ETABS programme has realised a design in the form of an excessive tensile force in isolators and has demonstrated the benefits of using this material.

Using seismic isolation, which has become an important branch of earthquake engineering today, superstructure responses can be reduced significantly. The period of the superstructure is extended and the damping is increased by introducing seismic isolators between the superstructure and the base. Lead Rubber Bearings (LRBs), which are widely preferred in base-isolated structure design, should be selected by taking the characteristics of the superstructure into account. Furthermore, the parameters of the isolation system should be determined to provide the best seismic performance. Within the scope of this study, the influence of the shear strain limit values on the design of seismically isolated buildings, which is one of the main design parameters for LRB type isolators, is investigated. Comparisons are made for 200% limit as defined in the Turkish Building Earthquake Code (TBDY-2018) and 250% limit as defined in other international regulations or applied in design practice worldwide. Cost analysis of LRB units is carried out for the aforementioned shear strain limit values with an approximately same seismic performance target defined as the shear force transferred to the superstructure. In order to make a comparison, a benchmark seismically isolated building is used.

Sustainability is a concept created by the environmental scientists in the 1980s and has a significant impact on building design. At first glance, sustainability can be understood as the uninterrupted continuation of the benefits as they were designed throughout the life of the buildings. In addition, it can be considered as the ability of the building to continue its function without disrupting the design purpose in the event of facing natural disasters such as earthquakes. The importance of the concept of sustainability is more remarkable especially in geographies where the seismicity is high. By making use of seismic isolation as an earthquake-resistant design method, post-earthquake sustainability can be easily realized as it allows to practically achieve the uninterrupted performance level after a major earthquake. Aside from earthquake resilience, a sustainable building design should also consider other aspects such as effective energy use, effective water management, and effective heating and cooling and aim to reduce the burden of these systems in terms of costs by using natural resources in the most efficient way. Green roof systems are among the main elements of sustainable building design, which absorbs rainwater, creates a habitat, provides insulation, and decreases the stress of the people around the roof by providing a landscape, and helps to lower urban air temperatures. Within the scope of this study, as a sustainable building example that takes both earthquake and environmental issues into account, a benchmark base-isolated building with a green roof system is described and its seismic performance under a historical near-fault earthquake record is compared to its fixed-base counterpart. Nonlinear time history analyses are carried out to obtain main structural response parameters including inter-story drifts, floor accelerations, and story shears which directly relates to sustainability. Comparisons are carried out in terms of the aforementioned structural response parameters.

In this paper, the addition of extra floors to existing buildings is suggested as a strategy able to increase the usable surface area offered in historic city centres with almost no land consumption, and, contemporarily, to improve the seismic response of the building structures. Starting from the definition of IIS spectrum for exploring the design effectiveness of this solution in the elastic case, a design framework and a five-step chart-based design procedure are suggested for utilizing IIS design spectra also in the case of existing buildings with inelastic behaviour. The procedure is validated by contrasting the outcome of the application to a case study to the numerical results obtained from NTHA of thirty-five 2DOF models, representing thirty-five design solutions for the isolated vertical extension of the case study. Extension and generalization of the procedure are also briefly discussed, considering different shapes of code design spectra.

Numerous strong earthquakes have highlighted the global vulnerability of key structures, such as seismically isolated buildings, tall skyscrapers, major pipelines, tunnels, large storage tanks, and long-span bridges, to near-fault and long-period ground motions. Consequently, evaluating the impact of long-period seismic excitations on these critical structures has become increasingly important. This paper introduces a new generation Structural Seismic Isolation Method (SSIM) and System (SSIS), designed to protect Highly Reliable Structures (HRS) against intense earthquakes, including those with near-fault and long-period ground motions. This innovative method aims to address the limitations and vulnerabilities of the Conventional Application Method of Seismic Base Isolation Devices (CAMSBID).The SSIM approach utilizes existing conventional elastomeric isolators with periods of up to 4 s, transforming the structure into an SSIS. This results in the structure exhibiting an inverse pendulum behavior, thereby extending the natural period of the structure beyond the predominant period of most earthquakes, including near-fault pulses. This paper details the characteristics, evaluation, efficiency, and application results of the SSIM method and SSIS system on high-rise buildings, nuclear containment structures, and tower structures. The findings demonstrate that SSIS structures experience significantly lower response levels compared to those using the CAMSBID method, and they do not resonate during seismic events.

In this paper, closed-form expressions are derived for tracing some displacement spectra to be used for the preliminary design of Intermediate Isolation System (IIS), with specific reference to the case of IIS obtained through isolated vertical extension of existing buildings. The so-called Intermediate Isolation System (IIS) design spectrum provides the drift in the lower structure varying the isolation period, thus allowing for identifying the design solution that maximizes the mass damping effect on the lower structure. The IIS design spectrum is derived by means the pole allocation method applied to two-degree-of-freedom model. Indeed, using the pole allocation method, it is possible to obtain the value of the modal damping ratios in closed form for non-classically damped systems, such as IIS. Known such modal damping ratios, it is possible to apply the CQC modal superposition method in response spectrum analysis, thus obtaining the IIS design spectrum. Similarly, it is possible to obtain the isolators displacement spectrum, to determine the design displacement of the isolation devices, which implicitly considers both the mass damping effect and the flexibility of the lower structure. Finally, the lower structure and isolator responses derived from these design spectra for IIS are compared with the ones obtained from linear time history analyses.

As technology of base isolation is getting more popular, it also widens the fields of its application. It is logical to apply base isolation for very important structures (hospitals, schools, theatres, etc.), but it also becomes as a good solution for safety of buildings, and also people and content inside the structures with different fields of use. In that sense, use of base isolation in research centres, laboratories and institutes becomes more common. In the north of Serbia, in Novi Sad, a state-of-the-art research building is being built for the BioSense Institute with financial support from the European Union. The part of the building with laboratories is provided with base isolation with integrated structure-borne noise insulation to protect and ensure smooth operation of the highly sensitive and capital-intensive technical installations. In addition, the decoupled laboratory module of the research building is provided with BIM-based building monitoring in order to be able to query and assess changes in the condition of the building at any time. This paper described the design and steps of installation of base isolators. Furthermore, results of on-site measurements (before, during and after construction) are presented. Sliding isolation pendulum (SIP) isolators incorporating polyurethane plate are presented as a one-package solution for both seismic and vibration isolation. Main characteristics of the system are presented. Its ease of installation and effectiveness of such a system presents big potential for the use in practice for different cases in practice (theatres, metro stations, hospitals etc.).

This paper studies the seismic performance and resilience of two different seismic designs of a 6-story steel building at a near-fault site in Los Angeles: (i) a fixed-base special moment frame (FB-SMF); and (ii) a base-isolation using triple friction pendulums and a SMF for the superstructure (BI-SMF). The fixed-base design is optimized to satisfy the minimum strength requirements of ASCE 7–16 (basis of the International Building Code, IBC-21), while the base isolated design exceeds the code minimum requirements to enhance seismic performance and reduce functional recovery time. The triple pendulum isolators are designed in accordance with the Seismic Isolator Standard for complying with ASCE 7–16 requirements for achieving target reliability of structural stability. The two buildings are analyzed using three-dimensional nonlinear response history analysis for eleven site-specific horizontal ground motion pairs developed for the design earthquake as well as risk-targeted maximum considered earthquake. The nonlinear behavior of the isolation devices as well as that of the SMF is explicitly modeled. The response is quantified in terms of story forces, drifts, and floor accelerations. A seismic loss and functional recovery time comparison of the designs is conducted using the SP3 platform. The study indicates the significant improvement of seismic performance and reduction of functional recovery time using base-isolation. The limitations of the code-minimum analysis procedure for the fixed-base SMF are revealed.

This paper is regarding the design of seismic isolation system with excellent seismic isolation performance by the arrangement that minimizes the difference between the center of mass and stiffness using NRB and LRB. The earthquake motions used in the seismic response analysis consider the soil property. As a result of performing the seismic response analysis using the RESP F3T program, the reduction of the response acceleration with excellent seismic isolation effect and the safety margin of the seismic isolator was confirmed. The quality reliability of the seismic isolator was guaranteed by obtaining a normal distribution for the production test results of the manufactured isolator.

The advantages of Seismic Isolation (SI) can be exploited in seismic retrofit of existing buildings. The strong reduction of acceleration offered by SI allows an impressive improvement of the performance of old buildings, designed without taking into account earthquake at all, or for a seismicity level much lower than the one required by present standards. An additional advantage of SI compared with conventional strenghtening techniques is that the retrofit works can be limited at one floor (usually the basement, plus the foundation), without any strenghtening intervention on the superstructure. Consequently, the building can be mantained in use during the retrofit works. In Italy, seismic retrofit of buildings with SI became relatively common after the 2009 L'Aquila earthquake, initially on buildings strongly damaged by the earthquake and declared uninhabitable. Recently, retrofit with SI is continuosly increasing, even in areas not recently affected by earthquakes. Now the Italian buildings retrofitted with SI are about 1/3 of the total number of seismically isolated buildings. Both private and public buildings are included. Most of said buildings are in reinforced concrete framed structure, but some old masonry monumental buildings have been seismically isolated as well. The paper describes the typical techniques used to insert the isolators in existing buildings, and a case study of a masonry building is shown in detail.

The Kaohsiung Buddhist Hall is a 2-story reinforced concrete building located in Kaohsiung City, Taiwan. The building is rectangular in plane with about 26.2 m in length, 17.8 m in width, and 11.12 m in height. The roof form of the hall is an arc arch, and a tower is at the front center of the building with a height of about 31.4 m. Because a new construction will be conducted on the site of the Kaohsiung Buddhist Hall, the relocated engineering of the Kaohsiung Buddhist Hall should be carried out, which could revitalize and promote urban development. Since the age of the building is more than 50 years, the aseismic capacity of this building could not meet the current aseismic code, and consequently, a retrofit design of the building structure should be required. The existing appearance of the Kaohsiung Buddhist Hall would be changed with excessive structure retrofitted. In order to decrease the amount of structure retrofit, a seismic isolation system under the foundation of the building, with friction pendulums, will be designed to reduce the seismic force to meet the requirements of the seismic design code. For meeting the latest regulations of the seismic design code, the efficacy of the seismic isolation system will be analyzed by response spectrum and time history dynamic analysis.

Seismic isolation is an earthquake protection system showing an increasing trend in the world, and over the past few decades, there has been a notable increase in the implementation of seismic isolation techniques in Turkey. Considering the seismicity of Turkey, seismic isolation provides many advantages to new-built and existing structures as a result of minimizing seismic action. Seismic isolation is predominantly employed in newly built structures such as hospitals, bridges, data centers etc. in Turkey, the first examples of these systems in existing structures are Marmara Başıbüyük Hospital and Moda Gurup Apartment as a residential building. Marmara Başıbüyük Hospital has been retrofitted with a conventional system in 2002 following the Düzce Earthquake, and the hospital hasn’t started operation since changing the seismic design code including the new chapters about the retrofit of the existing structure in 2007. After Düzce earthquake, the new retrofitting system with seismic isolation units has been required for all hospital with 150 beds and more by the Ministry of Health. The hybrid isolation system which has a combination of lead rubber bearing (LRB), pot bearing, and sliding-type elastomeric bearing has been used in the isolation system. In Moda Gurup Apartment Project, the seismic isolation system has been preferred by the tenants because of protecting the current constructional area avoids the smaller footprints and reduces the floor number according to the new construction plan. The hybrid system with LRB and elastomeric bearing (slider) is used at the foundation level. In both examples, the seismic acceleration and displacement limits for the global system are determined according to the superstructure performance under the design earthquakes. The system selection, design and installation details of these projects will be discussed in this paper.

Petrochemical plants located in seismic zone areas are at risk of experiencing damage to their equipment and in the most severe cases, potential harm to human lives. In some cases, after a strong earthquake, it might be required to initiate a temporary shutdown to plan the necessary repairs and replacements of damaged components to restore the standard safety level. The implementation of a base isolation system as a common passive control seismic protection technique can effectively mitigate the risk of damage to the structure by minimizing the ground-transferred energy induced by earthquakes to the superstructure. This paper focuses on conducting a seismic assessment of a typical steel petrochemical plant retrofitted with base isolation system. The study employs probabilistic approaches to estimate the probability of failure at different damage levels and also considers soil-structure interaction, to provide more realistic predictions of the seismic performance. Fragility curves are generated according to the response of the structure to earthquake strong motions. The results demonstrate that employing base isolation in existing petrochemical plants significantly reduces structural damage occurrence. This study is useful in designing and implementing protection and rehabilitation strategies to prevent and control further damage.

An increasing number of important structures, such as tall buildings, long-span bridges, large storage tanks, major pipelines, and tunnels, and most importantly, seismically isolated structures render the rational characterization of long-period ground motion for their reliable earthquake-resistant design. As such, the assessment of long-period ground motion has gained growing interest in the structural engineering discipline. The importance of the long-period component of earthquake ground motion has been recognized worldwide during numerous strong earthquakes. Two types of ground motions, with their own unique properties, are considered long‐period strong earthquake ground motion. One of them is the harmonic earthquake ground motion, which reflects the earthquake’s specific source and propagation characteristics on the surface waves and/or the soil amplification effects in deep sedimentary basins, the so-called basin response effects. The other one is the near-fault, pulse like earthquake ground motion, generated mainly by the rupture directivity effects. The philosophy of the direct displacement-based design, which has gained recognition as a more rational approach to designing earthquake-resistant structures, essentially relies on the displacement response spectra. Although there are several physical models and the associated numerical techniques to simulate ground motions, they do not give consistent results, and their indiscriminate use does not necessarily yield reliable estimates of ground motions for design. The application of methods for earthquake-resistant design based on displacement demand is thus affected by the inaccurate definition of spectral response in the long-period range. There is a strong need for the development of robust and reliable techniques for the assessment of long-period earthquake ground motions, especially for near-fault conditions. This paper will review and discuss the issues involved in the frequency and time domain characterization of strong ground motion in the long period ranges including displacement spectrum, peak ground displacement, basin response effects, and near-fault effects with relevant code stipulations regarding the design of the seismically isolated structures. Emphasis will be placed on the near-fault pulse-type long-period ground motions.

Seismic isolation is one of the most effective protection techniques used against seismic events all over the world. It can be easily used in different types of structures, especially for new constructions. While the basic concepts are almost similar in all countries, some specific rules and standards are different in each country. In this paper, the design of a base isolated building according to the Italian code is presented for comparison with other codes. The building is a seven-storey reinforced concrete condominium. Two isolation systems, composed of high damping rubber bearings and sliding devices, were designed according to the Italian Technical Code. For the seismic input, the Italian site with the maximum horizontal acceleration was chosen, with soil type C. The results can be easily compared with those obtained using other technical codes.

Non-structural components such as mechanical and electrical equipment that are used in buildings have started to be used more extensively in proportion to the increasing need for comfort. Mechanical and electrical equipments with higher capacity is selected to meet energy demands such as heating-cooling, ventilation, and electrical power in larger projects serving a relatively dense population. These high-capacity non-structural components generate vibrations while operating, and the vibrations may cause discomfort in the nearby areas in terms of vibration and noise where the equipment is located.In this study, an electric generator was modeled on different floors of a 5 story school building that was modeled in the ETABS structural analysis software. The generator was installed on vibration-isolating supports which are steel-cabin spring mount. Artificial BCJ-L2 seismic ground motion was input into the building model. In addition, the horizontal seismic force acting on the generator was calculated by equivalent seismic load method and non-linear time history analysis methods according to the Turkish Building Seismic Code 2018 (TBSC-2018) and American Society of Civil Engineering Code 7–22 (ASCE 7–22). Results obtained from the codes are compared with the values obtained from the dynamic software analyses.It was observed that dynamic responses increase in the upper floors. A revision was proposed for TBSC-2018 to reflect more accurate results. When the design values obtained from the codes are compared to the dynamic analyses results ASCE results are generally on the conservative side, and results from TBSC should be increased by modifying the relevant coefficients.

Earthquakes occur frequently throughout the world, and the loss of life, damage to property, and loss of dwellings of people in earthquake-prone areas have been very serious, seriously compromising the safety of human life and property. The most effective measure to mitigate earthquake disasters is to carry out seismic strengthening and isolation and shock-absorbing design of engineering structures. Some regions of China and Türkiye are in more active seismic zones, the losses caused by previous major earthquakes are large, and the damage to buildings is severe. Therefore, the comparison of China’s seismic code, isolation code and Türkiye’s seismic code will play a better role in promoting the design of building seismic resistance and isolation. This paper analyses the seismic response spectrum and seismic action of the two codes and analyses the similarities and differences of the isolation design in China and Türkiye through actual cases.

Under the sponsorship of General Directorate of Highways of Turkey, a new specification is developed for the seismic isolation design of highway and railway bridges. This paper describes the distinct features of the newly developed seismic isolation bridge design specifications of Turkey in comparison to AASHTO Guide Specifications for Seismic Isolation Design of Bridges and EN15129: European Standard on Anti-Seismic Devices. The comparative study is performed for different sections of the design specifications including the parts related to; (i) the classification of bridges for analysis and design, (ii) seismicity and design response spectra, (iii) equivalent linear and time history analyses, (iv) types of seismic isolation and energy dissipation devices covered in design specifications, (v) design of seismic isolation and energy dissipation devices, and their minimum testing requirements and (vi) minimum requirements of seismic isolation and energy dissipation devices to ensure continued functionality and serviceability of the bridge. The comparative study revealed that the new Bridge Seismic Isolation Design Specifications of Turkey differs in many ways compared to AASHTO and EN15129 including the approaches related to the seismicity and design spectra with particular emphasis on near-field effects, minimum requirements for the serviceability of bridges, property modification factors used for seismic isolation and energy dissipation devices as well as testing procedures.

The Mw 7.7 Pazarcık and Mw 7.6 Elbistan earthquakes which occurred on February 6th, 2023, had devastating effects in 10 cities at Southwest Turkey. It is notable that several base isolated hospital buildings were constructed in the region during the past decade. These isolated hospital buildings are unique such that they experienced two very strong earthquakes in a very short time span. Therefore, it is of significant importance to investigate their seismic performance after the February 6th earthquakes. In this study, effects of the Kahramanmaraş earthquakes on the base isolated hospital buildings in the region are inspected. The isolator displacements of the hospital buildings are determined during a site visit to the earthquake region by the authors and compared with the analytical predictions obtained from nonlinear dynamic analyses. The findings are also evaluated in comparison with the isolator design displacement demands of each hospital project. The data obtained from the site visit also documents the inappropriate seismic gap and infill wall applications in the constructed projects and resulting nonstructural damages in the isolated superstructures.

During the devastating 2023 Turkey-Syria earthquake sequence, hospital functionality in the affected provinces was considerably reduced to approximately 30–70% capacity due to collapsed or heavily damaged healthcare facilities, as well as significant nonstructural damage to lightly or moderately damaged facilities. The Adana City Hospital, the world’s second largest seismically isolated medical facility and one of the largest trauma centers in the region, was located in one of 11 heavily-hit provinces. While older buildings, as well as other modern hospital facilities – including select seismically isolated hospitals – typically designed for collapse prevention or life safety performance goals, lost functionality or operated at reduced capacity, the large, 1,550-bed Adana hospital successfully withstood the disaster with no structural or nonstructural damage and retained 100% functionality. The present paper presents the main design criteria and stringent seismic response limits used for the design of the structure and isolation system, which consisted of 1,512 Triple Pendulum™ isolators engineered by Earthquake Protection Systems, Inc., to deliver continued post-earthquake functionality of the facility, in accordance with the Seismic Isolator Standard (SIS). The early activation of the Triple Pendulum™ isolation system and special design features effectively enabled an estimated 75% reduction in seismic base shear demands on the supported structure and successfully protected its structural and architectural components, medical equipment, and MEP installations. Potential design and construction issues in other seismically isolated hospitals that did not exhibit the target performance of the facility or the isolation system they were designed for is also briefly mentioned.

February 6, 2023, earthquakes are one of the most destructive cascading earthquakes of the last century. Following the February 6, 2023, earthquakes, the official death toll exceeded 60000 in Türkiye and Syria, and hundreds of thousands of injuries were reported from healthcare facilities in the earthquake-affected region in Türkiye. Since hospital buildings are critical facilities, their seismic performance is expected to outperform the seismic performance of residential buildings during major earthquakes. Moreover, base-isolated facilities should meet the continued functionality as declared by the circular of the Ministry of Health enforced in 2013 and 2018 for hospital buildings with a bed capacity of over 100 in high-seismicity regions. In the earthquake-affected region, eleven seismically isolated hospital buildings and hundreds of conventionally constructed healthcare facilities were subjected to two main shocks and aftershock sequences during the February 6, 2023, earthquakes. In this study, the seismic performance of fixed-based and seismically isolated hospital buildings was examined under varying levels of earthquake ground motions during the February 6, 2023, earthquake sequence based on the preliminary findings of field trip observation.