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This study illustrates the development of a modeling strategy for simulating the seismic response of structures mounted on elastomeric bearings with a low shape factor (LSF). These bearings can be employed to achieve a three-dimensional seismic isolation of structures, due to their low vertical and horizontal stiffness. The first part of this work investigates the mechanical behaviour of LSF bearings by means of three-dimensional Finite Element (FE) analysis in Abaqus. The FE results provide a numerical evaluation of the horizontal, vertical, and rotational stiffness of the bearings. These are used in the second part of the study to develop in SAP2000 a simplified model of a structure with LSF bearings tested experimentally on the shaking table at University of Naples Federico II. The study results show that the developed model can be effectively used to simulate the response of the isolated structure under different earthquake inputs.

We report the experimental demonstration of a Mach-Zehnder-Fabry-Perot hybrid fiber interferometer. Preliminary characterization shows low background and good stability with an all-passive isolation system.

There is a need to reduce the seismic demand on buildings so that they can perform better during future earthquakes. This need can be fulfilled using the concept of base isolation. In this paper, a G+7 story framed structure has been analyzed to study the effect of base isolation on the seismic performance of structures. The most common type of isolation system, i.e., laminated lead rubber bearing (LLRB) has been designed, and response of the base isolated building has been compared with conventionally designed earthquake-resistant building. The computer program SAP 2000 has been used for modeling and analysis. Reinforcement requirements for both the buildings have been compared, and it has been found that base isolated building requires about 30% less steel than a conventionally designed building for the same level of seismic protection. To compare the nonlinear response of the conventionally designed building and base isolated building, nonlinear static pushover analysis was performed.

The goal of this paper is to find out the optimal parameters of cab’s isolation system to improve the ride comfort of the vibratory roller. A half-vehicle ride dynamic model of a single drum vibratory roller is established under various operating conditions. The design parameters of cab’s isolation system are optimized by the root mean square (rms) values of acceleration responses of the vertical driver’s seat (aws) and cab’s pitch angle angle (awcphi) according to the ISO 2631:1997(E) standard. A genetic algorithm (GA) and a multi-objective optimization algorithm are used for searching for the optimal design parameters of cab’s isolation systems. The study results indicate that the aws and awcphi values with GA optimal parameters reduce by 31.88% and 31.27%, respectively in comparison with the original parameters of cab’s isolation systems when the vehicle moves on the ISO class D road surface at the vehicle speed v = 5 km/h, which shows that the performance of the optimal parameters of cab’s isolation system is better than that of cab’s original isolation system in improving the ride comfort of a single drum vibratory roller at all operating conditions.

Background: The current SARS-CoV-2 pandemic has provoked the collapse of some health systems due to insufficient intensive care unit capacity. The use of continuous positive airway pressure (CPAP) and high-flow nasal oxygen (HFNO) therapies has been limited in consideration of the risk of occupational infection in health-care professionals. Aims: In preclinical experimental simulations, evaluate occupational and environmental safety of the newly developed isolation system for aerosol-transmitted infections (ISATI). Method: Simulations were conducted to test ISATI's capability to isolate aerosolized molecular (caffeine), and biological (SARS-CoV-2 synthetic RNA) markers. Caffeine deposition was analyzed on nitrocellulose sensor discs by proton nuclear magnetic resonance spectroscopy. Synthetic SARS-CoV-2 detection was performed by reverse transcription-polymerase chain reaction. Results: ISATI demonstrated efficacy in isolating molecular and biological markers within the enclosed environment in simulated conditions of CPAP, HFNO and mechanical ventilation therapy. Neither the molecular marker nor substantial amounts of synthetic SARS-CoV-2 RNA were detected in the surrounding environment, outside ISATI, indicating appropriate occupational safety for health-care professionals. Conclusion: Aerosolized markers were successfully contained within ISATI in all experimental simulations, offering occupational and environmental protection against the dissemination of aerosolized microparticles under CPAP or HFNO therapy conditions, which are indicated for patients with acute respiratory infections.

Many utility companies are converting overhead (OH) main line feeder sections to underground (UG) to improve reliability, system resiliency, or other local customer demands. A Hybrid distribution feeder is one with a mixture of OH and UG main line sections. Conventional protection philosophies for hybrid feeders normally result in lower overall feeder reliability. This paper will examine an example feeder to demonstrate the impact of protection and isolation system improvements on predicted reliability for Hybrid distribution feeders.

To enhance the normal service adaptability and seismic resistance performance of isolation continuous bridges, a superelastic-sliding lead rubber bearing (SSLRB) isolation system was devel...

This paper presents a vibration isolation system based on elastomeric mounts acting together with an electromagnetic actuator that can provide a force that, depending on the operating conditions, can amplify or attenuate the overall restoring force. Therefore, the device would have the advantage of behaving like a normal passive isolation system but, if necessary, its reaction can be controlled. To evaluate its effectiveness an isolator prototype was realized; it is constituted by three coils, two of which are placed on the ground while the last one is fixed on isolated structure. The tests were performed considering a unidirectional motion. In the paper, the experimental setup is described and the test results are presented and commented

The negative stiffness offered by bi-stable mechanisms can improve the dynamic performance of a structure. In this work the effects of adding negative stiffness and shape memory alloy (SMA) damping in base-isolated structures are explored through the study of the stationary response for different values of negative stiffness and SMA hysteretic damping ratio. The frequency response curves of the isolated structure, with and without the negative stiffness contribution, are numerically obtained for different levels of excitation amplitude in order to evaluate the acceleration and displacement transmissibility curves. The benefits of negative stiffness, damping amplification and reduced transmissibility of accelerations and displacements, as well as the existence of dynamic instabilities, are illustrated.

This paper presents the isolation performance of a three-dimensional base isolated Sodium-cooled Fast Reactor building. The three-dimensional isolation system consists of rubber bearing with the horizontal oil damper for the horizontal isolation system and disc spring units with vertical oil dampers for the vertical one, where the vertical one is set under the horizontal one to be arranged in series. These elements excepting the horizontal oil damper have been developed for the three-dimensional isolation system through the static or the dynamic loading tests using a full scale or a half scale model. Regarding the horizontal oil damper which is necessary for the three-dimensional isolation system as well as the horizontal isolation system, the details would be described in Part 6. The authors also have been tackled to create the analytical modeling for each element such as the disc spring units, vertical oil damper and rubber bearing. The previous studies from part 1 to part 4 clarified that the newly analytical model, each of which is defined by the differential equations, could accurately express relationships between the force and displacement of each element. To demonstrate the reduction effect (performance) of the seismic responses for the three-dimensional isolation system, the seismic response analyses using newly analytical modeling were performed for the Sodium-cooled Fast Reactor building that is modeled into the multi-degree-of-freedom-system. The isolation performance of the three-dimensional isolation system is verified through the floor response spectra evaluated at the position where the primary components are placed, in comparison with those by the conventional 2D horizontally isolation system using the rubber bearing without the vertical elements.

The design of seismically isolated structures has been required not only for damping devices with large damping capacities but also for those with high allowable velocities. This is because the seismic response assessment has been conducted using various ground motions, with high acceleration levels, to increase the structural integrity of buildings and components. However, the research focused on increasing the allowable velocity remains to be largely limited because the research involves a testing machine problem as well as a technical problem to increase the allowable velocity. To solve these problems, the authors have developed a new oil damper for seismic isolation buildings with an allowable velocity that is two times higher than commercially available oil dampers, which is the largest damping capacity class in Japan, using the test machine with one of the largest dynamic loading performance in the world. This paper demonstrates the availability of the proposed oil damper through the following items: The first is to clarify the damping force characteristics on the basis of the test results up to the maximum input velocity of 2.7 m/s. The second is to present the analytical model for the oil damper to apply to the seismic response analysis including the method to identify its variables. The third is to demonstrate the isolation performance through the seismic response analysis using the analytical model identified the variables obtained from the test results. These results imply that the proposed oil damper will be able to contribute to expanding the feasible design range for the isolation technology as well as increasing the seismic safety margin of the components for SFR.

Sustainable development not only deals with the protection of environment but also with the development that can be sustained for generations. Large part of the world is subjected to earthquake forces, which demands that structural engineers have to design the buildings so that it can withstand the consequence of these earthquakes. In order to mitigate this problem, seismic base isolation technique is used in recent years. In seismic base isolation, laminated rubber bearing (LRB) is the most extensively used technology, because of its fruitfulness and reliability. The principal purpose of seismic isolation is to lessen the seismic demand on structure. Isolation works on the principle of increasing structural time period. Hence decreasing the vulnerability of earthquake demand on the structure. In urban environment, for the purpose to provide parking facility at the ground storey of building, the concept soft storey has taken its place. However, the buildings with soft storey are most vulnerable to earthquake. In Bhuj earthquake (2001), most of the buildings damaged were of soft storey type. This investigation is to find out the efficacy of laminated rubber bearing isolation system in managing the reciprocating action of the soft storey frame model for the installation of isolation system at the top and at the bottom of soft storey column when subjected to El Centro, 1940 ground motion by using state-space method and a comparison is made between structures with and without infill wall. The response behavior in terms of absolute acceleration, inter storey drift, and storey shear have been investigated, for example, building models. With the use of isolation system, storey shear for all storey level is reduced. When LRB is placed at bottom of soft storey column base shear is reduced by 31.91% and absolute top floor acceleration is reduced by 42.23% that of soft storey building with fixed base.

© 2020 Elsevier Ltd A large number of studies and applications have been carried out on horizontal seismic isolation systems, and their effectiveness has been indicated. For long-span spatial structures, vertical seismic load plays an important role. However, vertical seismic isolation technology has not been extensively investigated. In this paper, a hybrid bearing with three-directional seismic isolation effects is proposed, in which the triple friction pendulum component and the viscous damping component are combined in series. Compared with other seismic isolation systems, the advantages of this hybrid seismic isolation system are that it can not only greatly lengthen the structural periods but also dissipate the seismic energy in all three directions. A hybrid numerical modeling method for this hybrid seismic isolation bearing is also developed. The seismic performance of a welded large-scale single-layer lattice dome with this hybrid seismic isolation system subjected to near-field ground motions is analyzed. The results show that the important dynamic demands in the dome are significantly suppressed compared with the base-fixed dome. The seismic isolation effects are evaluated in all three directions, and the effectiveness of the hybrid isolation system is verified. Finally, a comparative study is performed, and the mechanical parameters of this hybrid bearing are discussed. It is found that the damping energy dissipation in the seismic isolation bearings is not the most important factor in reducing structural dynamic demands. The proposed seismic isolation system and its numerical modeling method provide an attractive and effective alternative for the design of long-span spatial structures with hybrid seismic isolation systems.

COVID-19 has now become a global epidemic, prevailing over 213 countries of the world including Pakistan. To date, there have been more than 12000 cases and above 220 deaths reported in Pakistan. The outbreak is caused by a β-coronavirus called SARS-CoV-2, similar in characteristics to the SARS and MERS-CoV. It shows symptoms like pneumonia and may lead to death. Despite lockdown and possible isolation system, it is spreading rapidly. Lack of precautionary measures, specific vaccine and delayed diagnosis may be the major reasons for its spread. Several researches on COVID-19 have described its various features to extend its knowledge in order to help the scientific world in preparation of vaccine. Current review aimed to cover all essential data such as clinical characteristics, pathology, detailed morphology and structure, antigenicity of COVID-19 virus, role of structural proteins in anti-viral drug development and possible treatments being used. This manuscript would be helpful to select the best possible treatment depending on the availability and condition of the patient. Moreover, further research is needed for assistance in designing a virus-specific drug or vaccine.

BackgroundSARS-CoV-2 has high transmissibility through respiratory droplets and aerosol, making COVID-19 a worldwide pandemic. In its severe form, patients progress to respiratory failure. Non-invasive mechanical ventilation restrictions and early orotracheal intubation have collapsed health systems due to insufficient intensive care unit beds and mechanical ventilators. COVID-19 dedicated healthcare professionals have high infection rates. This publication describes experimental testing of the Protection and Isolation System for Patients with COVID-19 (PISP/COVID-19).MethodPISP/COVID-19 is a disposable transparent polyethylene plastic that covers the patient’s entire hospital bed, with its internal air aspirated by the hospital’s vacuum system attached to a microparticle filter. Experiments validated PISP/COVID-19’s ability to block aerosolized microparticles dissemination. Caffeine was used as a molecular marker, with leakage evaluation through sensors analysis using nuclear magnetic resonance spectroscopy. The biological marker was synthetic SARS-CoV-2 RNA, using Reverse Transcription Polymerase Chain Reaction (RT-PCR) as the detection method.ResultsPISP/COVID-19 was effective against molecular and biological markers environmental dispersion in simulations of non-invasive ventilation, high-flow nasal cannula oxygen and mechanical ventilation isolation. Caffeine was not detected in any of the sensors positioned at points outside the PISP/COVID-19. The ability of PISP/COVID-19 to retain virus particles and protect the surrounding environment was confirmed by detection and gradients quantification of synthetic SARS-CoV-2 RNA by RT-PCR.ConclusionPISP/COVID-19 was effective in the retention of the molecular and biological markers in all tested simulations. Considering the current pandemic, PISP/COVID-19 might increase the use of non-invasive ventilation, high-flow nasal cannula oxygen and provide additional protection to healthcare professionals.

Vibration of the automotive engine has the characteristics of wide frequency band, multi-vibration sources and multi-main frequencies. Limited capability of passive mounting systems can be provided for engine vibration isolation. A MR semiactive mounting system for automotive engines is investigated in this paper. The dynamic model of the vertical vibration isolation system for the engine and an efficient damping control model of the MR mount are established. The frequency characteristics of the engine vibration are analyzed. The fuzzy control algorithm for the MR mounting system is designed, and the isolation performance of the MR mounting system is analyzed based on the developed experimental setup in Hefei University of Technology.

Aerial manipulators have many important application scenarios, such as inspection and maintenance, search and rescue, structure assembly, and logistics. One important challenge in aerial manipulation is related to the vibrations induced on the manipulator and its end-effector by the Unmanned Aerial Vehicle (UAV), which significantly affect the grasping and manipulation precision/performance. In this paper, vibration analysis of a heavy payload octocopter has been carried out using Experimental Modal Analysis (EMA). A simplified Mass-Spring-Damper (MSD) dynamic model of the system has then been proposed, whose dynamic parameters have been identified by analyzing selected experimental modes of vibration. The identified model will be useful for the design of the manipulator and related vibrations isolation system.

Irregularity in plan can significantly increase the vulnerability of structures exposed to strong earthquakes. Application of base isolation systems is one of the possible solutions to avoid the negative effects from irregularity of structures in plan. In order to investigate the advantages of the application of these systems, a detailed evaluation of the behaviour of four five story reinforced concrete frame structures was performed. All structures are rectangular in plan and are analysed as fixed base and base isolated. The fixed base models differ between them according to the degree of irregularity. Because base isolated models have a significantly lower eccentricity between the centre of stiffness and the centre of masses, these models are regular in plan. Total obtained displacements in base isolated models are higher, but main part of them are concentrated at the level of the isolation system which results with lower interstorey drifts and small floor rotations.

The structural isolation is usually considered as the most effective technology to resist earthquake action. At first, motion equation of isolated structural system is derived. Then, in the section of basic characteristics of isolated structural system, response analysis and characteristics of isolated structural system are introduced. In the section of commonly used isolation devices for building structures, rubber isolation system, sliding isolation system and hybrid isolation system are introduced systematically.

This chapter is dedicated to present some methods for vibration protection of statues and cultural heritage objects against earthquakes and ambient vibrations. The chapter opens with short explanation about the dynamic performance test that has been done on a full-scale copy of the famous statue of Michelangelo Buonarroti Pieta Rondanini and its isolation system. Based on the results of the tests, a multidegree-of-freedom model is developed. This updated model is used to verify the proposed vibration control strategies. To reduce the level of vibration transmitted to the statue, combination of inerter with TMD (TMDI) is proposed. Optimal parameters of the passive device are found by using numerical methods. Furthermore, a scaled isolation system is designed and manufactured according to the test results of the full-scale structure. To improve the performance of the isolator, a designed and manufactured ball-screw type inerter is introduced to the scaled structure. The effectiveness of the manufactured inerter on the dynamic behavior of the isolation system is demonstrated by using dynamic performance tests on a shaking table. The results provide some numerical and experimental results considering inerter-based methods in order to vibration protection of statues and cultural heritage.

This paper assesses the safety of a double conical rolling isolation system designed for protecting telecommunications equipment using a probabilistic approach. Due to the limited number of input accelerograms in the GR-63-CORE guideline for telecommunications equipment (only one), eight different filters are optimized to best capture the required response spectrum. The fitted filters are incorporated into an easy-to-implement framework, which is used to generate several suites of accelerograms for the probabilistic analyses. The results of these analyses are analyzed and discussed to reveal the shortcomings of the GR-63-CORE guideline, which in general are the limited number of accelerograms and ignoring the potentially important low frequency accelerations in the prescribed accelerogram. It is shown that the prescribed accelerogram may not be representative of excitations that are expected to be experienced by telecommunications equipment or the isolation systems protecting them, and is, hence, not conservative. Moreover, the results of the probabilistic analyses are presented in the form of fragility curves that can guide the design of rolling isolation systems.

Rolling isolation systems (RISs) have been used extensively to protect vibration-sensitive equipment, such as server cabinets, from earthquake-induced floor motions. These systems are commonly installed in multi-unit arrays to isolate multiple cabinets from harsh floor motions. The mathematical model presented in this paper is an extension of an experimentally-validated model for a single-unit RIS and is amenable to an arbitrary number of isolated cabinets. The proposed model is first compared to free response tests and is then validated with forced response tests using a synthetic waveform representative of earthquake-induced floor motions. An extensive numerical parameter study using the proposed model is carried out to assess the influence of the number of isolated cabinets, as well as mass eccentricity, on the seismic isolation performance of these systems. Through an incremental dynamic analysis it is shown that systems with more cabinets are less prone to impacts, indicating better performance. Rotations produced in the presence of mass eccentricity may induce premature impacts transverse to the loading direction diminishing these systems’ performance.

Interest in integral abutment bridges (IABs) from the industry has increased in recent years. IABs are robust bridges without joints and bearings and hence they are durable and virtually maintenance free; moreover, the resulting cost-saving associated with their construction is significant, a fact that makes IABs appealing to agencies, contractors and consultants. However, their use in long-span bridges is limited by the complex soil–structure interaction. Thermal movements, horizontal loads and dynamic actions are transferred directly to the backfill soil, leading to settlements, ratcheting effects, high earth pressures and deterioration of the backfill soil. The longer the integral bridge the greater the challenge, as movements are increased. This paper provides an extended review of the techniques used in the international literature and in practice to alleviate the interaction between a bridge abutment and the backfill. Subsequently, the performance of an innovative isolation system for IABs using recycled tyres as a compressible inclusion is studied using detailed numerical models of a representative three-span IAB. The proposed isolation scheme was found to be an effective and sustainable method to isolate the structure from the backfill soil, reducing the pressures experienced by the abutments and the residual vertical displacements of the backfill soil.

This study focuses on experimental investigation of a fail-safe, bi-linear, liquid spring magnetorheological damper system for a three-dimensional earthquake isolation system. The device combines the controllable magnetorheological damping, fail-safe viscous damping, and liquid spring features in a single unit serving as the vertical component of a building isolation system. The bi-linear liquid spring feature provides two different stiffnesses in compression and rebound modes. The higher stiffness in the rebound mode prevents a possible overturning of the structure during rocking mode. For practical application, the device is to be stacked together along with the traditional elastomeric bearings that are currently used to absorb the horizontal ground excitations. An experimental setup is designed to reflect the real-life loading conditions. The 1/4th-scale device is exposed to combined dynamic axial loading (reflecting vertical seismic excitation) and constant shear force that are up to 245 and 28 kN, respectively. The results demonstrate that the device performs successfully under the combined axial and shear loadings and compare well with the theoretical calculations.

This article presents an analytical study of the seismic collapse performance of seismically isolated buildings and comparable non-isolated buildings. The study is based on archetypical 6-story perimeter frame seismically isolated buildings designed with special concentrically braced frames (SCBF), ordinary concentrically braced frames (OCBF) and special moment resisting frames (SMF) for a location in California using the minimum criteria of ASCE/SEI 7-10 and ASCE/SEI 7-16 and also using a number of enhanced designs. The isolation system consists of triple Friction Pendulum (FP) isolators with stiffening behavior at large displacement. Additionally, double concave sliding isolators are considered and designed per minimum criteria of ASCE/SEI 7 and without a displacement restrainer, a practice permitted by the standards. Non-isolated structures, also with braced and moment frame configurations, are designed using the minimum criteria of ASCE/SEI 7 and studied. The study concludes that seismically isolated buildings designed by the minimum criteria of ASCE/SEI 7 of either 2010 or 2016 may have unacceptable probability of collapse in the Risk-Targeted Maximum Considered Earthquake (MCER). The probability of collapse in the MCER becomes acceptable when they are designed with enhanced criteria of RI=1.0 and with isolators having a displacement capacity at initiation of stiffening equal to 1.5 times the demand in the MCER. It is also observed that designs that meet the minimum criteria of ASCE/SEI 7 of either 2010 or 2016 and without any displacement restrainer have unacceptably high probabilities of collapse.

The wide application of the ball-screw inerter for vibration isolation has made it increasingly important to precisely determine the vibration transmissibility of the isolation system. In this reported work, the transmissibility of a vibration isolation system containing an inerter was predicted by using a complex mass M* in the calculations. The reported theoretical analysis showed that in the design of the type II inerter-spring-damper and inerter-rubber vibration isolation systems, the inertance-mass ratio must be less than twice the damping ratio to achieve improved vibration isolation performance when designing the system. To validate the findings, experimental tests were conducted on the type II inerter-spring-damper and inerter-rubber vibration isolation systems with ball-screw inerter. The experimental results showed that, based on M*, the transmissibility of these two systems was close to the experimental results, which illustrated the rationale for using M*. The results of this reported study will help facilitate the parameter design and performance analysis of a vibration isolation system with an inerter.

Seismic isolation can be an effective strategy to protect critical facilities including Nuclear Power Plants (NPPs) from the damaging effects of horizontal earthquake ground shaking. The increased flexibility at the base and resulting elongation of the natural vibration period of the structure leads to significant reductions in forces and acceleration transmitted to the structure above the isolation level at the expense of displacements concentrated in the isolation system. Displacement demands can be large at sites of moderate to high seismic hazard and can be accommodated by a horizontal clearance or moat at the isolation level, typically located in the basement of a structure. A surrounding moat wall can function as a stop to limit isolation system displacements and prevent bearing failure under beyond design basis shaking. However, impact of the isolated structure against the moat wall is of concern due to potential amplification in response of the superstructure. Design guidelines aim to prevent impact by specifying a required minimum clearance to stop (CS) with a low annual frequency of exceedance. A CS below the required value can be justified through analysis considering impact to the moat wall or stop. However, little guidance is available on how to model impact to the moat wall and resulting effects on the NPP superstructure. This study proposes a simplified model for impact simulation that captures the impact forces and the effects of impact on the response of seismically isolated NPPs. Variable clearance to the stop and a range of properties for the moat wall and isolation system are considered to identify parameters that influence the response. Results of these studies indicate that large NPP plants as considered here can have significant penetration into the moat wall, and thus not fully limit displacements in the isolation system, while having considerable increases in accelerations throughout the height of the NPP model.

In order to improve the vibratory roller ride comfort, a multi-objective optimization method based on the improved genetic algorithm NSGA-II is proposed to optimize the design parameters of cab’s isolation system when vehicle operates under the different conditions. To achieve this goal, 3D nonlinear dynamic model of a single drum vibratory roller was developed based on the analysis of the interaction between vibratory roller and soil. The weighted r.m.s acceleration responses of the vertical driver’s seat, pitch and roll angle of the cab are chosen as the objective functions. The optimal design parameters of cab’s isolation system are indentified based on a combination of the vehicle nonlinear dynamic model of Matlab/Simulink and the NSGA - II genetic algorithm method. The results indicate that three objective function values are reduced significantly to improve vehicle ride comfort.

Urban densification represents one of the biggest universal challenges of contemporary cities: the increase of urban population requires new spaces to accommodate the growing demand for housing, working and tertiary activities. However, the land available for new constructions in highly urbanized areas is very limited. In this framework, the vertical extension of existing buildings is the most sustainable strategy and fascinating. Masonry structures , constituting a major part of the built stock in the historical city centres of several European countries, are particularly suitable for vertical addition of extra-floors, since they generally exhibit an adequate overstrength for bearing an increase of gravity loads, although seismic retrofit interventions are usually required. In this paper, starting from the case study of the historical town of Pozzuoli, in South Italy, an “antifragile” approach, based on the intermediate isolation system, is suggested to rise the height of the masonry building , while reducing the global seismic demand. For this aim, in this paper are analysed the architectural-functional and structural design issues related to a vast-scale application of vertical additions isolated on the top of existing structures. Further, the feasibility and effectiveness of the strategy are discussed, and benefits in terms of seismic performance are evaluated.

In the last 30 years, there has been a great development of seismic isolation systems. The most used are elastomeric type devices and frictional pendulum bearings. Although different, both types generate horizontal seismic isolation, but not vertical. This study presents a nonlinear three-dimensional seismic isolation system called vertical rocking isolation (VRI) system, based on devices called ISO3D. Unlike conventional seismic isolators, the ISO3D device is vertically flexible and laterally stiff. Although the proposed system can be applied to any type of structure, it is particularly attractive as a seismic protection system of special structures, such as fluid storage tanks supported on legs, power transformers and sensitive equipment with vertical acceleration. In this research an application to legged wine storage tanks is presented. Two models were studied: a 3 m 3 tank with 4 legs, and a 30 m 3 tank with 6 legs. The fluid-structure interaction was considered using a quasi-static approach, where the fluid behaves as a mass attached to the tank walls. Time-history analyses results show average reductions of axial loads and shear loads on the legs of 57% and 61%, respectively. Finally, a fragility analysis indicates that the PGA required to reach 50% of probability of failure increases by an average of 153% by using the VRI system.

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.

We hereby report on the incorporation of negative stiffness oscillators realized through Euler buckled beams within vibrating multilayered sandwich structures. Such devices have been extensively investigated as single degree of freedom isolation mechanisms when mechanical grounding is available. It is worth exploring the influences of implementing such mechanisms within continuous multilayered vibrating structures given their interesting nonlinear vibration isolation characteristics. A numerical investigation is presented in this work with the computed performance being compared against the one of linear oscillators of equal mass and damping properties. Despite the fact that the negative stiffness nonlinear (NSN) oscillators were not properly optimized for the specific application due to the implied computational cost, they exhibited superior performance to their linear counterparts in a broadband sense. Considering the dependence of the linear resonators’ performance to manufacturing precision and narrowband excitation, the NSN concept is an excellent candidate for attenuating structural vibration across a wide spectrum.

Historic buildings and cultural relics are valuable and must be preserved carefully. However, such structures may be destroyed during earthquakes owing to the deterioration of their structural performance over time. Therefore, retrofitting protection measures must be adopted. The typical structural style of ancient buildings in China and East Asia involves timber structures. Due to the diversity of the construction environment, the site conditions of such buildings are often unfavorable. Moreover, several important cultural relics in historic buildings exhibit low integrity, and therefore the primary structure must not be influenced during retrofitting. To overcome these problems, this paper proposes the use of an isolation system with a weak restoring force and post-earthquake recentering capacity. The proposed isolation system consists of elastic sliding bearings, laminated rubber bearings, viscous dampers and jack reaction joints. To better isolate lightweight structures under soft soil conditions, the stiffness of the isolation layer must be designed to have a low value, and therefore, the self-recentering ability cannot be realized. Thus, in this work, jack reaction joints were used to recenter the structure after a rare earthquake. Moreover, a performance index was introduced that is suitable for the seismic isolation protection of typical East Asian historic buildings. The proposed isolation system was applied to a famous historic timber building in Shanghai, namely, the Yufo temple, to improve the seismic performance of the translocated structure and nonstructural members. The underpinning system of translocation facilitates the use of the isolation system. The analysis results indicate that the proposed isolation method can help improve the performance of the structure involving both historic buildings and cultural relics and that the superstructure remains unaffected by the reinforcement measures. In addition, this approach can provide guidance for the protection of other cultural historical buildings that have different styles.

Explosion isolation systems provide critical protection for interconnected vessels and work areas, preventing the spread of explosions through interconnecting pipes and ducts. These systems not only prevent propagating events, but also mitigate the elevated explosion hazards of interconnected vessels, related to pressure piling and enhanced turbulence. Explosion isolation systems can, however, fail catastrophically when they are not properly designed for a use case. Evaluating the performance of explosion isolation systems includes assessing their pressure resistance, flame-barrier efficacy, and determining appropriate installation distances, which typically requires extensive testing. To predict the performance of a system for use cases outside the tested conditions, models are needed to reliably predict both the explosion dynamics and the isolation system response. In this study, a physics-based model for explosion dynamics in vented vessel-pipe systems is developed and validated. An extensive series of large-scale validation experiments were conducted, including tests using an 8 m3 vessel with attached pipes, varying the pipe dimensions, ignition location, and mixture reactivity. The model accurately captures the effects of experimental parameters and predicts the time available for isolation systems to form a flame barrier. This model can help to predict installation distances and reduce the number of tests needed to comprehensively evaluate explosion isolation systems and their use cases.

The Bouc–Wen nonlinear hysteretic model has many control parameters, which has been widely used in the field of seismic isolation. The isolation layer is the most important part of the isolation system, which can be effectively simulated by the Bouc–Wen model, and the isolation system can reflect different dynamic characteristics under different control parameters. Therefore, this paper mainly studies and analyzes the nonlinear dynamic characteristics of the isolation system under different influence factors based on the incremental harmonic balance method, which can provide the basis for the dynamic design of the isolation system.

The numerical model of the series isolation structure was established by using the finite element software to simulate the dynamic behavior of the series isolation structure after explosions occurred at different positions, and study the dynamic response and failure mode of the series isolation structure under explosion load. The results show that the vertical displacement and speed of the beams on each floor show a certain regularity with the passage of time. When columns at different positions encounter explosive loads, they will cause local collapse and damage of the structure, and the damage is mainly distributed in the longitudinal and transverse ranges where the columns are located. Compared with the inner column, the structural damage caused by the explosion load on the corner column and side column is more serious.

Introduction:The equation of motion of the mega-sub isolation system is derived in the present study. Then, the parameter optimization of the mega-sub isolation system is studied to illustrate the effects of the damping and stiffness of the isolation devices on the reliability of the system.Methods:Moreover, based on the first passage mechanism, the calculation procedure of the dynamic reliability of the system is presented. In this procedure, the story drift of the structure is used as the evaluation.Results and Conclusion:Numerical example shows that when the damping ratio of the isolation device is given, the overall reliability of the structure increases at first then decreases with increased frequency ratio, when the frequency ratio is constant, the overall reliability of the structure increases with increased damping ratio. In addition, compared to the aseismic system, the overall reliability of the mega-sub isolation system is significantly improved.

The feasibility of an active low-frequency vibrational-isolation system with compensation of the dynamic forces on the housing by means of antiphase inertial forces is considered. This system effectively reduces the forces transmitted to the housing from vibrations of an elastically suspended mass in the low-frequency subresonance range.

This article deals with the study of optimum performance of isolated bridge systems under stochastic earthquake load considering uncertain system parameters. The conditional stochastic response quantities are obtained in random vibration framework using the state space formulation. Subsequently, with the aid of matrix perturbation theory using first order Taylor series expansion of dynamic response function and its interval extension, the vibration control problem is transformed to appropriate deterministic optimization problems. This requires two separate objective functions correspond to a lower and upper bound optimum solutions. A lead rubber bearing system for isolating a bridge deck from a pier is considered for numerical study to elucidate the optimum performance of isolated bridge deck system. Then a numerical study is performed to observe the effect of parameter uncertainty on the optimization of the isolator parameters and the response reduction efficiency. It is seen that neglecting the effect of system parameter uncertainty may overestimate the system performance.

Summary After an earthquake, non-negligible residual displacements may affect the serviceability of a base isolated structure, if the isolation system does not possess a good restoring capability. The permanent offset does not affect the performance unless the design is problematic for utilities, also considering possible concerns related to the maintenance of the devices. Starting from experimental and analytical results of previous studies, the restoring capability of Double Concave Friction Pendulum bearings is investigated in this paper. A simplified design suggestion for the estimation of maximum expected residual displacements for currently used friction pendulum systems is then validated. The study is based on controlled-displacement and seismic input experiments, both performed under unidirectional motion. Several shaking table tests have been carried out on a three-dimensional isolated specimen structure. The same sequence of seismic inputs was applied considering three different conditions of sliding surfaces corresponding to low, medium and high friction. The accumulation of residual displacements is also investigated by means of nonlinear dynamic analysis. Copyright © 2017 John Wiley & Sons, Ltd.