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A passive double triangular damping (DTD) device with equivalent negative stiffness is proposed in this study. The DTD device consists of transmission systems and triangular damping systems. A mechanical model was developed to describe the force–displacement relationship of a triangular damping system, while the feasibility of both the system and model was evaluated using experimental tests. The theoretical analysis demonstrated that DTD was a form of damping with equivalent negative stiffness, and the equivalent expressions were generated. Finally, the prospect of application in the DTD-controlled isolation system was explored using numerical simulation. The results revealed that DTD was more effective than a lead–rubber bearing in reducing isolator displacement and rooftop acceleration when subjected to ground motions. [ABSTRACT FROM AUTHOR]

Indonesia is a country that has a fairly high seismicity intensity. Therefore, Indonesia needs seismic protection. One of the earthquake protections is to use an isolator system. One type of isolator system that is widely available is LCRB (Lead Core Rubber Bearing). The long-term use of lead-lead in isolator cores can cause soil pollution, and the price of lead material is very expensive. Most rubber layers are obtained from the isolator's country of origin so researchers developed the use of local rubber originating from Indonesia. In this study, innovating isolator bearings using Indonesian local rubber with a core system on isolators that are filled using environmentally friendly materials and do not pollute the soil such as sand, resin, rubber, and HDPE named SCLRB (Sand Core Local Rubber Bearing), ECLRB (Epoxy Core Local Rubber Bearing), RCLRB (Rubber Core Local Rubber Bearing), and PCLRB (HDPE Core Local Rubber Bearing), The method carried out for the evaluation of core bearing performance using environmentally friendly materials is to use finite element simulation ABAQUS is used to evaluate bearing performance as well as mechanical behavior. The results of the simulation of elements to mechanical behavior found that the efficiency of the base isolator using local rubber and various core fillers is environmentally friendly, which provides considerable damping and stiffness improvements and effectively limits lateral displacement. The results of the element simulation analysis showed that the innovation of environmentally friendly materials sand, epoxy, rubber, and HDPE for isolator cores can replace lead in isolator cores that can pollute the soil. [ABSTRACT FROM AUTHOR]

Earthquakes are disasters that cause vibrations and can cause damage to infrastructures. Thus, there is an urgent need to provide safe buildings against severe earthquakes to avoid any structural failures. One of the most effective systems for buildings against earthquakes is the seismic isolation system. The study aims to analyze and evaluate the efficient configuration of the isolation system to the structural responses of the buildings against earthquakes. The method used was to introduce the isolation system between story levels by placing them on the floors. The most efficient results in terms of structural responses were when the isolations were placed at the 1st and 5th stories, e.g., building periods, inter-story displacements, story shear, and internal forces. Placement of isolations with better response was obtained for isolations located at two stories than only a story. This implied that it served more effectively and better in minimizing structural damage. The isolations were ineffective when they were located on the 7th story, the results indicated that the inter-story displacement and story shear were insignificantly affected. From the analytical results due to the earthquake load, it was also found that the isolations on the 1st and 5th stories experienced the most significant responses, whereas the placement on the 7th story had an insignificant impact in minimizing structural damage due to earthquake load. [ABSTRACT FROM AUTHOR]

This study introduces the first application of nonlinear signal‐based control (NSBC) to shake table experiments with sliding masses. NSBC utilising a nonlinear signal was specifically developed for nonlinear system control. In shake table experiments with a steel structure, it realised a seismic acceleration record on the table with near 100% accuracy even when the structure displayed nonlinear characteristics due to yielding of its components. Regarding the severity, sliding is stronger than yielding because of the rapid shifts of stick and slip states. Sliding is utilised for structural damage mitigation in seismic isolation systems, which are prominent devices in earthquake engineering. However, when sliding occurs on a shake table, it significantly jeopardises the table control. Thus, this study investigates the performance of NSBC to shake table experiments involving the phenomenon. First, this study examines the effectiveness of NSBC via numerical simulations on a shake table with a sliding interface, demonstrated by the Karnopp model, with a friction coefficient of 0.2. Subsequently, a linear model is designed based on the stability analysis of NSBC to assess stability margins obtained from different models. Experiments are performed by placing masses weighing approximately twice the table weight on sliding interfaces with friction coefficients of 0.2–0.4. In these experiments, NSBC with a reasonable linear model design realised expected acceleration records with sufficiently high accuracies, whereas inversion‐based control failed. This study verifies the effectiveness of NSBC for shake table experiments with sliding masses. [ABSTRACT FROM AUTHOR]

A passive double triangular damping (DTD) device with equivalent negative stiffness is proposed in this study. The DTD device consists of transmission systems and triangular damping systems. A mechanical model was developed to describe the force–displacement relationship of a triangular damping system, while the feasibility of both the system and model was evaluated using experimental tests. The theoretical analysis demonstrated that DTD was a form of damping with equivalent negative stiffness, and the equivalent expressions were generated. Finally, the prospect of application in the DTD-controlled isolation system was explored using numerical simulation. The results revealed that DTD was more effective than a lead–rubber bearing in reducing isolator displacement and rooftop acceleration when subjected to ground motions.

In order to improve the damping capacity of building isolation system, this paper studies the damping isolation control system of the building structure based on negative stiffness. In this paper, the dynamic equation of the damping isolation control system is derived and its parameters are optimized by H2 norm theory and Monte Carlo pattern search method. Taking the 5-story building structure as an example, this paper analyzes and evaluates the damping performance of the damping isolation control system of the building structure under the actual earthquake. The results show that negative stiffness can improve the damping capacity of traditional isolation system. Additionally, the negative stiffness ratio under the condition of stability, the smaller the negative stiffness ratio, the stronger the vibration reduction ability of the negative stiffness. The damping isolation control system of building structure based on negative stiffness shows good damping effect under the actual earthquake. [ABSTRACT FROM AUTHOR]

Friction pendulum bearings (FPBs) have emerged as critical structural isolation devices in the field of earthquake engineering. Extensive research and development efforts have led to the exploration and refinement of these bearings, resulting in the creation of various models with unique structural configurations and superior mechanical properties. This paper offers an in-depth review of the friction materials employed in FPBs, alongside an analysis of the mechanical performance and advancements in research regarding single-pendulum, double-pendulum, multiple-pendulum, and other types of friction bearings. Characterized by their low sensitivity and high stability, these bearings are adept at resisting seismic forces, thus providing dependable isolation protection for structures. This review also includes a succinct examination of the seismic performance and engineering applications of these isolation structures. With robust self-centering capabilities, excellent isolation, and energy dissipation mechanisms, FPBs are capable of quickly resuming normal operations post-seismic events. This reduces structural damage and maintenance expenses, significantly improving the seismic resilience of structures. Moreover, the paper outlines the current challenges in the research and development of FPBs and suggests future research directions, including optimizing friction materials, enhancing the design and performance of isolation structures, and improving the seismic performance and engineering application efficiency of FPBs. By identifying underexplored areas and synthesizing findings differently, this review provides a comprehensive and novel perspective that advances the field of earthquake engineering. [ABSTRACT FROM AUTHOR]

Predicting maximum displacement is an important task in designing any isolation system, including isolation systems using single friction pendulum (SFP) bearings. Many design codes allow an equivalent linear force (ELF) procedure to be used to predict this engineering demand, providing that the system satisfies some specific conditions. An ELF procedure is much simpler than a dynamic time-history analysis procedure because it does not require time-history inputs. However, this procedure is still time-consuming because it requires an iteration process. This study aimed to develop simple equations to directly calculate the maximum displacement without iterating. The database for developing these equations was obtained by performing the ELF procedure in a current standard on a wide range of isolation systems subjected to a wide range of ground-shaking strengths. As a result, a simple equation that can directly predict the maximum displacement of any isolation system using SFP bearings was proposed. The inputs to the equation include friction coefficient and concave radius of the bearings in the system and the 1-s spectral acceleration of the site. The proposed equation confidently predicts the maximum displacement calculated by the ELF procedure with an average displacement ratio, which is the ratio between the predicted and computed values, of 1.015. The minimum and maximum ratios in the investigated database were 0.975 and 1.092, respectively. [ABSTRACT FROM AUTHOR]

Predicting maximum displacement is an important task in designing isolation systems. An effective procedure that is widely used for this task is equivalent linear force (ELF) procedure, which is allowed by many contemporary design codes. This procedure uses very basic parameters of the isolation system as well as earthquake condition of the site to analyze for the maximum displacement. However, ELF procedures are time-consuming because they require an iteration process. This study employed an ELF procedure to generate a large database and used it to develop explicit and simple equations that can directly calculate the maximum displacement of isolation systems using lead rubber bearings. The proposed equations can confidently predict the maximum displacement calculated by the ELF procedure. In addition, the investigation showed that the first to post-yield stiffness ratio of an isolation system, which is difficult to accurately determine, has neglected effect on the maximum displacement calculated by the ELF procedure. Based on this observation, a simple equation that uses only three input parameters to predict the maximum displacement was proposed. The input parameters to the simplified equation include normalized characteristic strength and post-yield period of the isolation system, and 1-s spectral acceleration of the site. These parameters are minimum to determine an isolation system and earthquake condition. The comparison between the maximum displacement predicted by the proposed equation and the maximum displacement calculated by the ELF procedure showed that the proposed equation generates slightly conservative results for common designs, therefore is suitable for practical application. [ABSTRACT FROM AUTHOR]

To enhance the seismic resilience of bridges equipped with nonseismic laminated rubber bearings, a novel seismic isolation system is proposed, leveraging hybrid bonded and unbonded laminated rubber bearings. An experimental program is conducted to investigate the seismic behavior of this innovative hybrid bearing system. Cyclic loadings are applied to bonded, unbonded, and hybrid bearings to assess their force-displacement hysteretic response, energy dissipation, and restoring performance. The experimental findings reveal that unbonded rubber bearings exhibit significant energy dissipation through sliding but show limitations in restorability. Conversely, bonded bearings demonstrate superior restoring capacity but offer limited energy dissipation. The proposed hybrid bearings, combining bonded and unbonded bearings, achieve a favorable equilibrium between energy dissipation and restoring performance. Compared to individual bonded and unbonded bearings, the hybrid bearings exhibit a remarkable increase in energy dissipation by 110 % and restoring performance by 185 %. Furthermore, a numerical simulation method is proposed to accurately capture the critical hysteretic behavior of the hybrid bearings. ● A novel bridge isolation system with hybrid bonded and unbonded laminated rubber bearings is introduced. ● The cyclic hysteretic behavior of hybrid bearing system is experimentally investigated. ● The energy dissipation and restoring performance of hybrid bearing system is evaluated. [ABSTRACT FROM AUTHOR]

Asymmetric damping forces induce the equilibrium position of the isolated body to shift downward. Inspired by this phenomenon, this paper proposes the novel concept of shifting an isolated body based on the vibration of nonlinear systems with asymmetric damping forces. To verify the feasibility of this concept, a piecewise smooth isolation system is established. The incremental harmonic balance method is used to analyze the nonlinear vibration system and to obtain a steady-state analytical solution. The accuracy of the solution is verified by the Runge–Kutta method. Based on the analytical solution, the influences of some key parameters on the system vibration response are analyzed, revealing that the shift in the isolated body height increases with increasing excitation amplitude and damping asymmetry ratio. Additionally, this shift first increases and then decreases with increasing excitation frequency, reaching a peak near the natural frequency of the intermediate body. Finally, considering the complex structure, high energy consumption, and slow response of active suspension actuators, the proposed concept is applied to the tilt control of a vehicle. The simulation results show that the proposed methodology based on this concept can tilt a vehicle body to a certain angle in the turning direction, enabling the use of a semi-active actuator for vehicle tilt control to realize the control effect achieved by an active actuator. [ABSTRACT FROM AUTHOR]

In this paper, a mechanical model of a transformer–bushing with an inerter isolation system (IIS) is established. An IIS is composed of an inerter element, a damping element, and a spring element connected in parallel between the same two terminals. Vibration control equations and frequency response functions are also established. The influence of parameters on IIS, including inerter–mass ratio, damping ratio, and frequency ratio, was studied. In the extremum condition that represents the most efficient parameter set of inerter–mass ratio and damping ratio for relative displacement response ratio, an optimal design method was developed by exploiting a performance demand. Finally, the seismic response of the transformer–bushing with IIS was carried out to verify the isolation performance of IIS. The research shows that the equivalent mass coefficient and damping coefficient of IIS can be amplified by an inerter element and the inerter–mass ratio and damping ratio are reduced simultaneously under the conditions of meeting the performance demand after parameter optimization. Meanwhile, the parameter optimization design method proved to be effective for meeting the target demand of the relative displacement response of the bushing and tank, while base shear force and isolation displacement were reduced simultaneously. Based on the results from a response history analysis under ground motion records, IISs can significantly suppress the resonance response of a structure and the continuous vibration response in the stable state. The peak displacement can be reduced by 50% compared with a traditional isolation system. [ABSTRACT FROM AUTHOR]

Story-added type apartments have recently been introduced as an option to resolve the housing supply shortage in areas that are undergoing rapid industrialization and urbanization. However, the infrastructure of old apartment buildings (>20 years old) makes it difficult to introduce convenient facilities and recent technologies such as those involving the Internet of Things and augmented realities. Applying housing technologies to existing older apartments can increase housing supply and potentially address the aforementioned issues. However, story-added building remodeling increases the weight of existing buildings, necessitating seismic reinforcement, which is the major obstacle when performing vertical building extensions. This study presents methods for lowering seismic loads associated with vertical augmentation of buildings while improving the seismic performance. A model of a vertically extended building with three additional stories constructed on top of an existing 15-story apartment building was used. The applied seismic isolation system decreased the maximum response acceleration on top of the remodeled building by approximately 70% and 65% in the X-direction and Y-direction, respectively, while decreasing the base shear plane by approximately 30% in both the X- and Y-directions in comparison with forces on a non-seismically isolated building. These results demonstrate that the use of a seismic isolation system can significantly reduce seismic loads. [ABSTRACT FROM AUTHOR]

This study evaluates the accuracy of an equivalent linear model in predicting peak nonlinear time-history displacement of seismic isolation systems with single friction pendulum bearings. To perform this evaluation, dynamic response of numerical models of 120 isolation systems subjected to 390 strong earthquake ground motions, including motions with pulse and motions without pulse, was analyzed and statistically processed. The results show that the equivalent linear model can partly predict the peak displacement of its counterpart nonlinear model. However, the equivalent model can also underestimate or overestimate the peak displacement. On average sense, the equivalent linear model underestimates small peak displacement and overestimates large peak displacement. It is also observed that the relationship between linear and nonlinear peak displacements depends on ground motion types. Based on the analysis data, equations representing relationship between linear and nonlinear peak displacements at different reliable levels for different ground motion types were proposed. These equations can be used in practice. [ABSTRACT FROM AUTHOR]

In order to improve the damping capacity of building isolation system, this paper studies the damping isolation control system of the building structure based on negative stiffness. In this paper, the dynamic equation of the damping isolation control system is derived and its parameters are optimized by H2 norm theory and Monte Carlo pattern search method. Taking the 5-story building structure as an example, this paper analyzes and evaluates the damping performance of the damping isolation control system of the building structure under the actual earthquake. The results show that negative stiffness can improve the damping capacity of traditional isolation system. Additionally, the negative stiffness ratio under the condition of stability, the smaller the negative stiffness ratio, the stronger the vibration reduction ability of the negative stiffness. The damping isolation control system of building structure based on negative stiffness shows good damping effect under the actual earthquake.

In this paper, a mechanical model of a transformer–bushing with an inerter isolation system (IIS) is established. An IIS is composed of an inerter element, a damping element, and a spring element connected in parallel between the same two terminals. Vibration control equations and frequency response functions are also established. The influence of parameters on IIS, including inerter–mass ratio, damping ratio, and frequency ratio, was studied. In the extremum condition that represents the most efficient parameter set of inerter–mass ratio and damping ratio for relative displacement response ratio, an optimal design method was developed by exploiting a performance demand. Finally, the seismic response of the transformer–bushing with IIS was carried out to verify the isolation performance of IIS. The research shows that the equivalent mass coefficient and damping coefficient of IIS can be amplified by an inerter element and the inerter–mass ratio and damping ratio are reduced simultaneously under the conditions of meeting the performance demand after parameter optimization. Meanwhile, the parameter optimization design method proved to be effective for meeting the target demand of the relative displacement response of the bushing and tank, while base shear force and isolation displacement were reduced simultaneously. Based on the results from a response history analysis under ground motion records, IISs can significantly suppress the resonance response of a structure and the continuous vibration response in the stable state. The peak displacement can be reduced by 50% compared with a traditional isolation system.

Different centers of mass (CMs) of a diesel engine were set to find their effects on the vertical vibration of an engine. To understand the effects and reduce vibration during sensing, we changed the location of the CM of the engine and performed a simulation to obtain data such as the vertical movements, velocity, torque, and acceleration of the vertical springs of isolators. The data showed that a 0.1 mm higher CM than the original CM of the engine reduced the amplitude of the vertical vibration by 4.35% and the velocity of the vertical vibration by 45.7% at a fixed rotation speed of the engine of 1000 revolutions per minute (rpm). Different CMs did not significantly affect the torque and acceleration. Instead, the phase of the vertical movements, the velocity, and the acceleration significantly changed with the CM in the simulation. The results imply that the CM needs to be considered in the design of the vibration isolation system of a diesel engine to increase the accuracy and lifetime of sensors used in vehicles under severe vibration conditions. [ABSTRACT FROM AUTHOR]

Story-added type apartments have recently been introduced as an option to resolve the housing supply shortage in areas that are undergoing rapid industrialization and urbanization. However, the infrastructure of old apartment buildings (>20 years old) makes it difficult to introduce convenient facilities and recent technologies such as those involving the Internet of Things and augmented realities. Applying housing technologies to existing older apartments can increase housing supply and potentially address the aforementioned issues. However, story-added building remodeling increases the weight of existing buildings, necessitating seismic reinforcement, which is the major obstacle when performing vertical building extensions. This study presents methods for lowering seismic loads associated with vertical augmentation of buildings while improving the seismic performance. A model of a vertically extended building with three additional stories constructed on top of an existing 15-story apartment building was used. The applied seismic isolation system decreased the maximum response acceleration on top of the remodeled building by approximately 70% and 65% in the X-direction and Y-direction, respectively, while decreasing the base shear plane by approximately 30% in both the X- and Y-directions in comparison with forces on a non-seismically isolated building. These results demonstrate that the use of a seismic isolation system can significantly reduce seismic loads.

The aim of this study is to propose an optimal design method for drum’s isolation systems of a double-drum vibrating roller so that the ride comfort can be improved. A half-vehicle ride dynamic model is established based on the drum-ground interactions. The weighted root mean square (rms) of acceleration responses of the vertical and pitch vibrations of the vehicle body (awb and awphi) according to the ISO 2631:1997(E) standard is chosen as objective functions. A genetic algorithm (GA) is applied for searching for the optimal design parameters of drum’s isolation systems based on the objective functions. The study results indicate that the awb and awphi values of GA optimal parameters reduce significantly in comparison with those of the original parameters of drum’s isolation systems, which means that the performance optimization of drum’s isolation systems is better than the original vehicle in improving the vehicle ride comfort. [ABSTRACT FROM AUTHOR]

In this study, we investigated the isolation effect of a curvature-consistent frictional pendulum bearing isolation system (CC-FPB-IS) on a long-span spatial structure. Considering a typical spherical reticulated shell in a long-span spatial structure as the research object, we conducted shaking table tests on a scaled reticulated shell structure equipped with fixed hinge bearings and CC-FPBs. In addition, a refined finite element simulation method was established to analyze to the seismic impact on an actual reticulated shell structure with isolation layers under different isolation conditions. The variations in the isolation effect on the dynamic responses under horizontal unidirectional, vertical, and three-dimensional ground motions were compared. The results indicated that the isolation layer comprising the CC-FPB can notably reduce the horizontal dynamic response of a reticulated shell structure under horizontal seismic action while retaining its elastic state during rare earthquakes. With increasing loading amplitude, the isolation rate of the long-span spatial structure increased and gradually reached the optimal value. However, the proposed CC-FPB-IS did not effectively reduce the dynamic response of the vertical component, and the isolation rate was relatively small. When subjected to a three-dimensional earthquake, the structure exhibited an isolation effect because of the coupling of earthquake components in different directions. Thus, the CC-FPB-IS has notable effects on the dynamic response of the overall structure. • A type of curvature-consistent frictional pendulum bearing isolation system (CC-FPB-IS) was proposed. • A series of shaking table tests were conducted on reticulated shell structure equipped with fixed hinge bearings and CC-FPBs. • The isolation effect of the CC-FPB-IS on the reticulated shell structure was obtained. • A refined finite element simulation method was established to analyse structures and isolation layers. • The CC-FPB-IS was applied to the actual long span spatial structure to analyse the influence law of isolation. [ABSTRACT FROM AUTHOR]

Summary: This paper evaluates the ability of simplified superstructure models, including two shear frame models and a single‐story model, in predicting global responses of a full‐scale five‐story steel moment‐frame buildings isolated by triple friction pendulum bearings subjected to earthquake motions. The investigated responses include displacement of the isolation system, roof drift, story drift, and floor acceleration. Mechanical properties of the simplified superstructure models were derived from the modal information of a verified full 3‐D model. The comparison between the analytical responses and experimental responses shows that the simplified models can well predict the displacement of the isolation system. Furthermore, the shear‐frame models are adequate for predicting floor acceleration when the specimen is subjected to horizontal ground motions. However, when the specimen is subjected to 3‐D motions, the shear‐frame models un‐conservatively predict floor acceleration. The full 3‐D model improves the prediction of story drift compared with the simplified models for both horizontal and 3‐D motions. [ABSTRACT FROM AUTHOR]

The use of base isolation system is one of the developments in civil structural engineering in order to protect structures under major earthquake loads. The concept of the use of the base isolation system is to increase structure’s natural period and to provide additional damping to the structures reducing or avoiding the structural damage significantly under major seismic loadings because the input energy from the seismic will be dissipated through the FPS mechanisms. The study implemented two types of friction pendulum bearing system (FPS) namely the Single and Triple Pendulums. In this research, the behaviors of the single and triple friction pendulums implemented in the reinforced concrete high rise buildings will be compared and discussed. The design method of FPS is based on the combination of ultimate load and response spectra complying with the Indonesian Standard SNI 1726-2012 standard. Seven time histories were implemented for non-linear analysis to study the performance of the structures. Parameters used to evaluate the performance namely base shear, inter-story drift, roof acceleration, degree of damage and energy dissipation resulting from the responses of these two types of FPS’s both under design based and maximum credible earthquakes.

Many buildings in Japan currently have a base-isolation system with a low stiffness that is designed to shift the natural frequency of the building below the frequencies of the ground motion due to earthquakes. However, the ground motion observed during the 2011 Tohoku earthquake contained strong long-period waves that lasted for a record length of 3 min. To provide a novel and better solution against the long-period waves while maintaining the performance of the standard isolation range, the exploitation of the characteristics of nonlinear damping is proposed in this paper. This is motivated by previous studies of the authors, which have demonstrated that nonlinear damping can achieve desired performance over both low and high frequency regions and the optimal nonlinear damping force can be realized by closed loop controlled semi-active dampers. Simulation results have shown strong vibration isolation performance on a building model with identified parameters and have indicated that nonlinear damping can achieve low acceleration transmissibilities round the structural natural frequency as well as the higher ground motion frequencies that have been frequently observed during most earthquakes in Japan. In addition, physical building model based laboratory experiments are also conducted, The results demonstrate the advantages of the proposed nonlinear damping technologies over both traditional linear damping and more advanced Linear-Quadratic Gaussian (LQG) feedback control which have been used in practice to address building isolation system design and implementation problems. In comparison with the tuned-mass damper and other active control methods, the proposed solution offers a more pragmatic, low-cost, robust and effective alternative that can be readily installed into the base-isolation system of most buildings. [ABSTRACT FROM AUTHOR]

The slender electrical equipment in substations is fragile to damage during earthquakes owing to the seismically sensitive structure, low material strength, and coupling effects from interconnected equipment. To improve the seismic performance of the slender electrical equipment in the interconnected circuit system, the design and characterization of an assembled isolation system were recommended. The solution was based on a novelty combination application of bolt-on isolators and a support block by reducing the bending stiffness of slender equipment to achieve vibration isolation function. The isolation function test was performed on isolators from characteristics of stiffness variation and damping. Finally, the effectiveness of the proposed isolation system was proved in seismic performance improvement of interconnected slender electrical equipment using a comparison shaking table test, which was performed on a full-scale interconnected circuit, consisting of two ± 800 kV composite pillar insulators connected by a tubular busbar. Therefore, thus isolation system can provide effective seismic protection for interconnected slender equipment in proper design. • An isolation for improving seismic performance of electrical equipment is proposed. • The isolation mitigates acceleration, strain, and displacement response. • Performance of the isolation increases as the amplitude of earthquake. [ABSTRACT FROM AUTHOR]

In this study, the seismic behavior of an existing steel cable-stayed bridge equipped with lead-rubber bearing subjected to moderate and strong earthquakes is investigated. The bridge is located at high seismic zone and experienced an earthquake in 1988 which caused the failure of one of its anchorage plate of the support. Herein, the bridge was modeled in three dimensions and the base isolators implemented at the abutments and deck-tower connection. The bridge seismic responses were evaluated through nonlinear dynamic time-history analysis. The comparative analysis confirmed that the base isolation system was an effective tool in reducing seismic force transmit from substructure to superstructure. Furthermore, the overall seismic performance of cable-stayed bridge significantly enhanced in longitudinal and transverse directions. However, it is observed that the axial force of the tower in substructure increased due to the isolation system induced torsional deformation to the superstructure under transverse seismic loads. [ABSTRACT FROM AUTHOR]

This paper presents the results of a theoretical study carried out to characterize the dynamic behavior of a seismic isolation system consisting of steel-rolling balls on rubber layers. This type of device reduces seismic hazard during earthquakes by decoupling the superstructure from the ground motion and by dissipating the energy in damping, thanks to the viscous-elastic properties of the rubber. The behavior of the rolling balls on rubber layers isolation system is described by achieving suitable expressions for the resultant normal and shear forces acting in the device. In particular, it is shown how the resultant shear force is highly affected by the correct definition of the slip and stick regions, which develop at the steel-rubber contact area. The analysis allows to identify the main parameters characterizing this type of device, furnishing a valid tool in order to correctly calculate some response quantities significantly influenced by the isolation system. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Multiple solutions are currently used, in constructions domain regarding the structure isolation against seismic actions, operating on different principles such as seismic energy dissipation or dynamic motions isolation. For these purposes, special mechanical devices are built, that embedded between the structural frames of a building manage to reach the stated purpose of improving the structure behavior during high magnitude seismic actions. In this paper an isolation system is described meant for the base isolation of structures based on the dry friction force principle. This is a composed device having from one to several spherical metallic friction surface plates that is mounted between the foundation and the superstructure of the building, ensuring freedom of movement for the foundation together with the ground when an earthquake occurs while the superstructure tends to remain in equilibrium position. [ABSTRACT FROM AUTHOR]

The achievement of new civil and industrial buildings or the rehabilitation of old ones involves using special systems designed to avoid the dynamic requests represented by shocks, vibrations or seismic actions. Such systems are already used worldwide in various modern building structures but also for bridges or viaducts. Whether it is about isolation or energy dissipative systems they provide a high degree of stability and safety in exploitation for the structures to which they are attached. Elastomeric bearings and dry friction based systems are already used for equipping bridges and viaducts structural types in order to avoid the sudden ground movements that can occur with the advent of an earthquake. This paper proposes an experimental model for a hybrid isolation system composed of elastomeric bearings and rolling pendulum system, disposed on the vertical direction in the same assembly. It is expected that from both systems a better isolation can be achieved against the effects of dynamic loads that affect the structures. Laboratory tests were carried out using a reduced scale experimental model of the hybrid isolation system and the results are shown in the following. [ABSTRACT FROM AUTHOR]

Abstract: Soil conditions have a great deal to do with damage to structures during earthquakes. This paper attempts to assess the influence of dynamic soil–structure interaction (SSI) on the behavior of seismically isolated cable-stayed bridge supported on a rigidly capped vertical pile groups, which pass through moderately deep, layered soil overlying rigid bedrock. In the present approach, piles closely grouped together beneath the towers are viewed as a single equivalent upright beam. The soil–pile interaction is idealized as a beam on nonlinear Winkler foundation using continuously distributed hysteretic springs and viscous dashpots placed in parallel. The hysteretic behavior of soil springs is idealized using Bouc–Wen model. The cable-stayed bridge is isolated by using high-damping rubber bearings and the effects of SSI are investigated by performing seismic analysis in time domain using direct integration method. The seismic response of the isolated cable-stayed bridge with SSI is obtained under bi-directional earthquake excitations (i.e. two horizontal components acting simultaneously) considering different soil flexibilities. The emphasis has been placed on assessing the significance of nonlinear behavior of soil that affects the response of the system and identify the circumstances under which it is necessary to include the SSI effects in the design of seismically isolated bridges. It is observed that the soil surrounding the piles has significant effects on the response of the isolated bridge and the bearing displacements may be underestimated if the SSI effects are ignored. Inclusion of SSI is found essential for effective design of seismically isolated cable-stayed bridge, specifically when the towers are very much rigid and the soil condition is soft to medium. Further, it is found that the linear soil model does not lead to accurate prediction of tower base shear response, and nonlinear soil modeling is essential to reflect dynamic behavior of the soil–pile system properly. [Copyright &y& Elsevier]

• Seismic performance of monopole transmission towers are evaluated. • Two benchmark concrete transmission towers are selected as case studies. • An isolation system is installed to improve the tower seismic performance. • Refined finite element models are built in OpenSees environment. • The overall responses of isolated towers are improved by the use of tendon elements. The seismic performance of monopole transmission towers under the near-fault earthquake excitations are evaluated in this paper and some innovative solutions are presented to enhance their seismic behaviour. To this purpose, two benchmark concrete transmission towers are selected as case studies. The towers differ in the used materials, which are high-performance and ultra-high-performance concretes. In order to improve the tower performance under seismic actions, an isolation system with and without tendon elements are installed. The tendon gross-sectional area, effective length, and post-tensioning force are considered as three important factors, which affect the behavior of the structure equipped with isolation system. The tower top acceleration and displacement responses are evaluated and used to identify the optimal ranges of the above-mentioned design parameters. Accordingly, detailed finite element models are built in OpenSees environment in order to conduct non-linear time-history analyses under some near-fault ground motions. The results of the analyses show that the application of the isolation system may improve the displacement response of the tower, but it may cause an increase of the acceleration responses due to the impact of the isolators with their external boundary. In contrast, the addition of the tendon elements with proper characteristics improves the overall responses of the isolated towers. [ABSTRACT FROM AUTHOR]

LNG storage tanks are specified to be designed to withstand the impact of large commercial aircraft, while the existing studies refer to the safety assessment of the base-isolated LNG storage tank are quite limited. At present firstly, the detailed finite element (FE) models of LNG storage tanks are established. Based on the scaled tests of RC slabs under the impact of deformable and non-deformable projectiles, the numerical algorithm, constitutive model and the corresponding parameters of concrete are validated, which can both reproduce the behaviors of bending and punching shear failure potential induced by the aircraft impact. Then, the energy dissipation capacities and relative constitutive model of isolation systems are evaluated and validated. The reliable FE models of base-isolated LNG storage tanks with three typical isolation systems are established Furthermore, by adopting the missile–target coupled method, the dynamic responses and damage failure of tanks under aircraft impact are assessed, it derives that, (i) the fuselage and engines impact regions of tank wall are locally perforated and penetrated, the connection between the inner steel wall and deck is torn, and the safety of tanks is hard to be guaranteed; (ii) the selection isolation systems have sufficient lateral stiffness to resist the excessive global deformation of the base-isolated LNG storage tanks under aircraft impact, different types of isolation systems and boundary conditions of tanks have slight influence on the local damage of tank wall. The present work could provide beneficial guidances for the design and safety assessment of the base-isolated large-scale LNG storage tanks under aircraft collisions. • Refined FE models of LNG storage tanks against aircraft collisions are established. • Numerical algorithm, constitutive model and parameters of concrete are validated. • Energy dissipation capacities and isolator are evaluated and validated. • Dynamic response and damage failure of tanks under A380 aircraft impact are assessed. [ABSTRACT FROM AUTHOR]

The Resilient-Friction Base Isolator (R-FBI) stochastic response under severe ground motion modelled as a stationary and non-stationary zero mean stochastic white noise processes is performed. The moment equation approach is applied and the non-normal response is obtained by means of a non-Gaussian closure technique, based on the Gram-Charlier asymptotic expansion of the response probability density function. Results are compared with the equivalent non linearization technique and with results obtained by means of Monte Carlo simulation. [ABSTRACT FROM AUTHOR]