Seismic Isolation Of Structures Research Articles

Seismic Analysis of Magnet Systems in Helical Fusion Reactors Designed With Topology Optimization

Superconducting magnets in fusion reactors are subjected to a huge electromagnetic force of >100 MN/m. The magnets have to be sustained with a strong-body structure to avoid high stress and deformation. The total weight of the magnet system in the fusion reactor is estimated to be more than 20,000 tons. We applied topology optimization technique to the magnet support structure to reduce the weight of fusion reactors. Compared with the conventional design, we achieved a weight reduction of >25%. Static and seismic analyses were carried out to validate the soundness of the topology-optimized design. Consequently, the stress against the electromagnetic force in the structure was within the permissible range. It was discovered that using seismic isolation structure can adequately prevent the damage to the magnet system even when directly subjected to a massive earthquake.

Integration Method for Response History Analysis of Single-Degree-of-Freedom Systems with Negative Stiffness

The present article deals with the mathematical investigation of a negative-stiffness ideal system that can be used in seismic isolation of civil engineering structures. Negative-stiffness systems can be used in the seismic isolation of structures, because in the case of a strong earthquake, they do not easily allow vibrations to develop. These negative-stiffness systems can be significantly more efficient than the usual seismic isolation systems, as they drastically reduce the vibrational amplitudes of structures, as well as eliminate the inertial seismic structure loadings. The mathematical investigation of a negative-stiffness ideal system provides documented answers about the effect of negative-stiffness systems in the seismic behavior of structures. First, the differential equation of motion of a single-degree-of-freedom oscillator (SDoF) is formulated, without classical damping, but with negative stiffness. Furthermore, the mathematical solution of the equation of motion is given, where it is proven that this solution does not describe a structure vibration. Furthermore, the seismic structure motion follows an exponential increase when the seismic ground excitation is purely sinusoidal. Finally, to calculate the real response of the negative-stiffness system, a suitable modification of the Newmark iterative numerical method is proposed.

Seismic Response and Economic Study of New Light Steel-Wood-Plastic Structure in Rural Yunnan, China

A new type of light steel-wood-plastic residential structure in rural has popular in recent years in rural Yunnan, China. The application of light steel, wood, and new plastic materials in practical engineering is gradually increasing due to its advantages of green ecology and waste utilization, and its response characteristics under earthquakes have attracted great attention. In this paper, seismic-resistant models, seismic-isolated models, and seismic-damped models for multistorey light steel-wood-plastic structures were established using the SAP2000 finite element software based on different seismic response methods. The seismic-isolated model is divided into five schemes, namely, LRB400, LRB500, LRB600, high damped, and friction pendulum-isolated bearings, and the seismic-damped model is divided into three schemes, namely, ordinary bracing, soft-steel bracing, and BRB bracing at the same locations around the 2nd floor of the building. Nonlinear time analysis was carried out for the nine schemes, comparing the period, structural interstorey displacement, base shear, top displacement, top acceleration, and economy of the structure under the action of an 8-degree earthquake. Results show that the period of the seismic-isolated system increased by approximately 130% compared to the seismic-resistant system, and the period of the damped system decreased slightly compared to the seismic system, the interstorey displacement, base shear, and top acceleration of both the seismic-isolated system and the damped system were smaller than those of the seismic-resistant system, and the seismic-isolated system decreased by approximately 40% compared to the damped system, and the seismic-isolated system was more effective than the damped system. From the comparison of postearthquake damage cost and full-cycle cost, the economic performance of the seismic-isolated structure is better than that of the damped and seismic-resistant structures. The conclusions of this paper can provide a scientific reference for promoting the use of new light steel-wood-plastic residential buildings.

Seismic Performance and Optimization of a Novel Partial Seismic Isolation System for Frame Structures

To improve the safety performance of important rooms, such as operating rooms and disaster command centers, during an earthquake, a novel partial seismic isolation system suitable for new and existing frame structures is proposed, and the seismic and optimization analysis is carried out. Using the finite element numerical simulation method, the models of the ordinary frame structure and the partial isolated system structures were established. Considering the seismic response of the isolation room, the design safety of the partial isolation room, and the seismic impact on the overall structure, this study analyzed the damping effect of the partial isolation system. We changed the type of isolation bearing, the location of the isolation room, and the load to further optimize the calculation of the seismic isolation structure. The results show that the new partial isolation system could significantly reduce the seismic response of the isolated room under the action of a magnitude-8 rare earthquake. The damping rate of the relative acceleration and relative displacement between the top and bottom of the columns of the isolated room could reach 90%. It was found that the partial seismic isolation system proposed in this paper was applicable to reinforced concrete frame structures and could significantly reduce the seismic response of the isolated rooms without affecting the seismic performance of the main building. This partial seismic isolation system is easy to construct, applicable to both existing and new structures, and provides a new and effective seismic mitigation measure to improve the seismic performance of locally important rooms in the structure.

Finite-Element Analysis of Vertical Displacement of Laminated Rubber Bearing under Earthquake Action for Disaster Resilience of the Smart City

With the construction and development of smart cities, higher requirements have been put forward for the prediction and control of major natural disasters. For the prevention of earthquake disasters in super high-rise buildings, the rubber bearings of high-rise seismic isolation structures may have the risk of tensile damage in high-intensity areas, which has always been an urgent problem to be solved. In this paper, a unidirectional horizontal compression-shear experiment with 400% large deformation was conducted on the laminated rubber bearing (LNR500), and the relationship curve of vertical displacement with horizontal displacement of the bearing was obtained. According to the experimental data, an ideal elastic-plastic principal structure model was selected for the steel and a Yeoh principal structure model was selected for the rubber material, and the finite element analysis was carried out for the bearing. The time course curves of displacement, velocity and acceleration of the vertical and horizontal deformation of the laminated rubber bearing under the earthquake were obtained.

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

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

State-of-Art-Review: Latest Advancements in Seismic Isolation of Structures

Seismic isolation is effected by providing an interface between the foundations of the building and superstructure which may consist of stories above the ground level by inserting devices. Those are meant to reduce the effect of ground motions generated by an earthquake or/ and wind load. In this process, the period of the whole structure including base isolators is elongated so that ground waves containing large energy contents in the horizontal components of the earthquake may be deflected conveniently. An updated state-of-art review of isolation techniques and the design of isolated buildings is presented in this paper. The research findings in the comprehensive form are extracted out of the large volume of research papers published during the last five decades, where only some limited quality papers are selected for the preparation of this manuscript. The review generally covered papers on the analysis and design of structures with base isolation. Review is not confined to buildings with friction pendulum isolators only, but also includes the study of structural response to some other types of base isolators and dampers to seismic attacks.

Study on Seismic Isolation of Long Span Double Deck Steel Truss Continuous Girder Bridge

In order to improve the seismic performance of long-span double deck steel truss continuous girder bridge, taking Dao Qing Chau Bridge in Fuzhou as an engineering background, the isolation scheme of friction pendulum bearing (FPB) and friction pendulum bearing combined with viscous dampers is applied to study seismic performance. A three-dimensional dynamic model of the bridge is established using SAP2000. Taking three artificial seismic waves as seismic excitation, the seismic response of the seismic structure is calculated by nonlinear time history integration, and is then compared with the seismic response of the seismic reduction and isolation structure. The results show that the friction pendulum bearing (FPB) scheme and combined seismic dissipation and isolation (CSDI) scheme show a good seismic dissipation and isolation effect and ensure the safety of the bridge structure. However, for whole-bridge isolation, friction pendulum bearing (FPB) will produce certain residual deformations and additional stress of the bearing under the conditions of temperature and external load. For the purpose of protecting the bearing, it is recommended to use the combined seismic dissipation and isolation (CSDI) scheme.

Progressive Collapse of the Base-Isolated Frame Structures Supported by Stepped Foundation in Mountainous City

Base-isolated frames supported by stepped foundation in mountainous areas possess their own particularity, so its progressive collapse dynamic response performance and dynamic effect propagation path are very different from those of ordinary flat ground-isolated structural systems. In order to study the progressive collapse performance of the base-isolated frames supported by stepped foundation in mountainous areas under two-directional coupled dynamic excitation, a four-span three-story plane frame demolition column test was simulated to verify the reliability of the computing platform. The common ground motion and three types of long-period ground motions were selected, and the two-dimensional dynamic coupling of the ordinary flat ground isolation structure and the base-isolated frames supported by stepped foundation in mountainous areas was obtained based on the demolition method. First, the seismic isolation structure was subjected to the collapse dynamic response under the vertical unbalanced load, then the collapse dynamic response under the vertical unbalanced load and the horizontal seismic coupling excitation was made; the two were compared and analyzed. It can be used as a reference for the design of progressive collapse of the frame structure of the base-isolated frames supported by stepped foundation in mountainous areas.

Evaluation of equipment fragility curve in isolation building considering the vertical seismic ground motion

Seismic isolation structures have been introduced in a wide variety of fields as devices to enhance safety during earthquakes. In the nuclear field, although many studies have been conducted for introducing seismically isolated nuclear reactors, this has not been realized yet. To ensure higher reliability and safety of seismic isolation systems, probabilistic risk assessment, which consists of seismic hazard analysis, seismic fragility analysis, and system analysis, plays an important role. This paper aims to investigate the effect of the ultimate characteristics of isolation devices and vertical ground motion on the damage risk of isolators and equipment on the building. As a result, in the case of the isolation layer, it was confirmed that the horizontal response dominates the risk since the effect of vertical motion tends to be small. On the other hand, when the natural period of equipment is approaching either a horizontal or vertical period of the isolation system, the risk of equipment is tended to be underestimated. Thus, the consideration of the effects of vertical motion in addition to horizontal motion and the ultimate characteristics of isolators should be required for the risk assessment of seismic isolation systems.

Study on the Impact of Hydraulic Fracturing on Surrounding Ancillary Buildings considering SSI

Hydraulic fracturing is a key technology in the development of unconventional oil and gas reservoirs. With the continuous industrialization and large-scale development of shale gas production in China, the workload of hydraulic fracturing is also increasing rapidly, and the induced seismic events are also increasing gradually, resulting in different degrees of damage to the surrounding ancillary buildings. In order to study the impact of hydraulic fracturing on ancillary buildings, the finite element software ABAQUS was used to establish a three-dimensional model of middle and high-rise isolated structures to simulate the earthquake triggered by hydraulic fracturing. Then, considering the SSI (soil-structure interaction) effect of soil-based structure, the nonlinear dynamic response of the structure under the action of ground motion was analyzed. Through the adoption of different types of soil and the foundation depth, the influence of various parameters is discussed. The study found that in the case of not considering SSI, basal shear force, and displacement between floors of the seismic-isolation structure significantly greater than considering SSI, using hard soil layer, base shear displacement is greater than the soft soil layer and interlayer, shows that due to the effect of hydraulic fracturing, making fluid diffusion in soil, the seismic energy dissipation effect. It is also found that the period, base shear, peak displacement, and interlayer displacement of deep foundation pit are increased compared with shallow foundation pit considering SSI effect.

TREND OF SEISMIC RESPONSES OF EXISTING HIGH-RISE RC BUILDINGS

This report presents studies on the seismic response of high-rise RC buildings in Japan. Data concerning the seismic response of approximately 600 high-rise RC buildings constructed from 1972 to 2015 were collected. Seismic response characteristics were analyzed by focusing on differences in seismic resistant structures, seismic response control structures, and seismic isolation structures. The results indicated that the maximum story drift ratio response under the level 1 study seismic ground motion (R) and the level 2 study seismic ground motion (R) criteria is smaller for seismic isolation structures than that of the seismic resistant structure and seismic response control structures. In addition, focusing on the R-R relationship, the correlation is low in the seismic resistant and seismic response control structures, but is almost linear in the seismic isolation structure. This is because the seismic isolation structure is designed such that the superstructure does not become plastic even with level 2 seismic ground motion.

Influence on the seismic isolation performance of friction pendulum system when XY shear keys are sheared asynchronously

When the friction pendulum system and shear keys work together to resist the ground motion, which obliquely inputs (non 45°) to the bridge structure, the shear keys in XY direction will be sheared asynchronously, so that the friction pendulum system will have a violent changing direction curve movement on the sliding surface under the earthquake, and there is a strong plane friction coupling effect during this process. In view of this situation, this paper constructs a Spring-Viscous damping-Coulomb friction plane isolation system with XY shear keys, which realizes the detailed and accurate mechanical analysis under the plane friction coupling effect of friction pendulum system, and adopts self-programming to realize the calculation of the time history response. The results indicate that when XY shear keys are sheared asynchronously, on the one hand, it will change the motion state of system, caused the influence of the plane friction coupling, on the other hand, it will cause a sudden change of the structural acceleration at the moment of the shear key sheared. While the shearing force of XY shear keys is small, the plane friction coupling effect will play a leading role, which will reduce the maximum acceleration of the structure. Meanwhile, the plane friction coupling effect caused by XY sheared asynchronously will increase the maximum relative displacement of the structure, and this amplification effect needs to be more importantly considered in the design of structural seismic isolation when the PGA is small.

Exploration into the Anti-Seismic Technologies in the Museum

The overall seismic isolation structure is adopted for Yunnan Provincial Museum. The paper explores anti-seismic technologies for both museum buildings and collections, offers seismic protection analysis and design for precious museum collections by taking into account seismic waves, buildings, exhibition facilities and collections as a whole. Based on the demand for protecting museum collections from earthquakes, the paper discusses proper anti-seismic technologies for the museum structure, exhibition facilities, showcases and collections; it offers the dynamic time-history analysis of seismic isolation structure in rare earthquakes, and gives anti-seismic analysis and design for collections based on the acceleration response of the floor on different levels. Conclusions: The seismic protection for museum collections shall take into consideration seismic transmission from the venue and structure to exhibition facilities, showcases and collections. Under seismic actions, the acceleration response of the floor of exhibition halls on different levels of the museum varies greatly, the seismic response of showcases reinforced with anti-seismic measures decreases significantly, which ensures the safety of museum collections in earthquakes. The paper focuses on the anti-seismic technical route, technical measures, assessment results and implementation suggestions, offering reference for the construction of new museums and the seismic preventive conservation of collections.

Seismic running safety of trains and a new type of seismic-isolation railway structure

Abstract Until now, seismic-isolation structures have not yet been applied in the railway field. The reason is that though a seismic-isolation structure can reduce the inertial force to the structure, the energy absorption causes big response displacement on the structure, which adversely effects the running safety of the trains supported by the structure. In this paper, a methodology for seismic running safety assessment is introduced, and a new type of seismic-isolation foundation is proposed, which can convert the seismic response displacement in the lateral direction of track to the longitudinal direction that has a less adverse effect on the running safety of the train. The isolation foundation is composed of FPS (Friction Pendulum System) slider, concave plate and guide ditch. Moreover, through model experiments and 3D numerical simulation, it is verified that the proposed foundation can keep both the effects of the seismic isolation and the running safety of the train during an earthquake.

Economic performance analysis of seismic isolation, energy dissipation, and traditional seismic structures

The construction of a new countryside requires a compr hensive improvement in the building standards of villages and towns, and the seismic resistance of buildings in earthquake-prone areas has attracted much attention. Due to the backward economic development of villages and towns, the development of seismic isolation structure and energy dissipation structure is hindered. To build houses with better seismic performance, the economic efficiency of seismic isolation and energy dissipation structures has become a matter of close concern to the local people and the government. This article compares the economic differences between the original seismic structure, the base isolation structure, and the seismic damping structure from the costs incurred during the entire life cycle of the building, and provides economic reference for the new rural seismic isolation building.

Friction Measurement Method of Seismic Isolation Structure with Sliding Bearrings

Friction Measurement Method of Seismic Isolation Structure with Sliding Bearrings

Proposed minimum restoring force requirements for seismic isolated structures

In this research study, a new set of restoring force equations are proposed for seismic isolated structures subjected to far fault ground motions (FFGM) and near fault ground motions (NFGM). For this purpose, 110 FFGM and 49 NFGM are selected. Then, nonlinear time history analyses (NLTHA) of SDOF seismic isolated structures are performed using the selected ground motions to obtain their residual and maximum displacements. The analyses are repeated for an extensive range of parameters including peak ground acceleration, Ap, characteristic strength, Qd and post elastic period, Td, of the isolation system. Next, the variations of the residual and maximum displacements are plotted as functions of the various combinations of the parameters considered in the analyses. Then, nonlinear regression analyses are performed to formulate the residual and maximum displacements as functions of the parameters considered in the analyses. The developed equations are then used to formulate the upper limits of Td (restoring force equations) to ensure reasonable levels of residual and maximum isolator displacements. The developed restoring force equations are then compared with those of AASHTO and Eurocode-8 (EC-8) using the pool of residual and maximum displacement data obtained from NLTHA. It is observed that using the restoring force equations of AASHTO and EC-8 to check the design of seismic-isolated structures may, in some cases, produce unreasonably large levels of residual and maximum displacements. However, when the restoring force requirements proposed in this research study are applied, the residual and maximum displacements are observed to be within reasonable ranges.

Analysis of Seismic Isolation Effects on a Reverted L-shaped Pier Bridge in High Seismic Intensity Region with Finite Element Simulation

The seismic response of urban special-shaped bridges is large, and the consequence of these bridges’ failure is very influential, therefore, the seismic response of this kind of bridges must carefully be calculated and seismic measures of isolation should be used for them. Simulation methods was studied for common used seismic isolation structures such as the rubber bearing, high damping rubber bearing, friction pendulum bearing and block. Four layouts of those seismic structures were set up for an actual reverted L-shaped pier bridge, which were correspondingly four simulation cases. The seismic responses of the bridge were analyzed and comparatively studied in all simulation cases, as a result, the seismic performance and seismic isolation effects of those structures were researched for the bridge, and the isolation design methods were gained. The results show that measures of isolation can reduce largely the seismic response of this kind of special-shaped bridge, high damping rubber bearings have remarkable effect and make the responses among piers more even, and setting reasonably blocks with clearance can make full use of the seismic performance of structures of the bridge.

Horizontal-Vertical-Rocking Coupled Response Analysis of Vertical Seismic Isolated Structure under Near-Fault Earthquakes

For vertical isolated structures with excessive vertical eccentricity for mass and vertical stiffness, horizontal-vertical-rocking response needs to be better understood for vertical isolated structures located in near-fault areas, where long-period velocity pulse can be produced. In this study, a seismic isolation system including quasizero stiffness (QZS) and vertical damper (VD) is used to control near-fault (NF) vertical earthquakes. The responses of horizontal-vertical-rocking coupling base-isolated structure including quasizero stiffness (QZS) and vertical damper (VD) subjected to NF horizontal and vertical ground motions are investigated. Nonlinear dynamic analyses are conducted to study the effects of essential parameters such as isolation system eccentricity, static equilibrium position, vertical isolation period, and vertical damping ratio on seismic responses of vertical isolated structure. It is found that increasing vertical period and damping ratio causes the vertical isolated structures to behave well in reducing rocking responses of structure. The effect of horizontal-vertical-rocking coupling on vertical seismic isolation efficiency is insignificant. The vertical seismic isolation remains effective as compared to the system supported on rubber bearings. The vertical damping can significantly control the vertical displacement and rocking moment.