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This study investigates the modification in the seismic response of a base-isolated bridge that is exposed to low temperatures. The isolation system is assumed to be composed of lead rubber bearings (LRBs). The parameters considered in this study (experimental and analytical) are the temperature (0°C, −10°C, and −20°C) and exposure time (3, 6, and 24 h). In the experimental section, a large-sized LRB was subjected to displacement-controlled cyclic motions once it had been conditioned at the desired low temperatures and exposure times. The recorded force–deformation relationships were used to construct deteriorating hysteretic bilinear representations for each loading condition. Then, in the analytical section, several bidirectional nonlinear response history analyses were conducted using the idealized bilinear representations. In the analyses, two sets of ground motion records that were representative of different seismicity levels were selected and scaled in accordance with the codified procedures. The exposure time is a key parameter that needs to be considered in the estimation of the maximum isolator forces (MIFs) that are transmitted to the bridge piers. For the selected parameters, the MIFs of the analyzed bridge model could increase up to 30% with a trend to increase with the increasing exposure time. [ABSTRACT FROM AUTHOR]

To improve the ability of seismic isolation of flexible building structures, an air spring-lead rubber bearing (AS-LRB) three-dimensional seismic isolation device with both horizontal and vertical seismic isolation was proposed. The structure of the three-dimensional seismic isolation device was introduced, and the horizontal and vertical mechanical properties of the three-dimensional seismic isolation device were experimentally studied. In addition, the calculation method of the horizontal and vertical mechanical properties of the three-dimensional seismic isolation device was proposed. The research results show that the three-dimensional seismic isolation device uses an air spring (AS) for vertical seismic isolation and lead rubber bearing (LRB) for horizontal seismic isolation. The load-displacement curve of vertical seismic isolation exhibits nonlinear characteristics, and its vertical mechanical properties are obviously affected by the air pressure of the AS. The energy consumption capacity of horizontal seismic isolation is strong, and its horizontal mechanical properties are obviously affected by the loading amplitude and the air pressure of the AS. Through comparison with the test results, the proposed calculation method can accurately calculate the horizontal and vertical mechanical properties of the three-dimensional seismic isolation device. [ABSTRACT FROM AUTHOR]

This paper introduces a novel method to spontaneously predict displacement time histories and hysteresis curves of bridge lead rubber bearings under seismic loads and axial forces. The method leverages a stacked convolutional‐bidirectional Cuda Long Short Term Memory network, enhanced with multi‐head attention, skip connections, exponential learning rate scheduler, and a hybrid activation function to improve performance. The framework utilizes the functional application programming interface provided by the Python Keras library to build a model that takes input features such as horizontal and vertical ground accelerations, actuator loads in both lateral and vertical directions, and the superstructure mass. The effectiveness of the deep learning model is evaluated using a considerable experimental dataset of 53 real‐time hybrid simulations, spanning various earthquake intensities and superstructure masses (Chi‐Chi: 15 scenarios, El Centro: 15 scenarios, Kobe: 13 scenarios, and Northridge: 10 scenarios). Initially, Northridge earthquake data serves as unseen data, while the rest is used for training and validation. In a subsequent trial, the unseen data is centered on Kobe earthquake scenarios. By employing a hybrid loss function merging mean square and mean absolute errors, the model exhibits a substantial correlation of over 83% between predicted displacement time series and empirical measurements for the unseen data. In summary, the proposed model offers miscellaneous benefits, including time and cost savings in experimental efforts by decreasing the need for additional tests. It further delivers a swift and precise insight into the bridge bearing performance and its energy dissipation, facilitating timely and accurate bridge design in different scenarios for engineers. [ABSTRACT FROM AUTHOR]

Damage to bridges during a seismic event can cause significant disruption to post-event activities. In addition to natural hazards, the deterioration of bridges over their lifespan also significantly impacts seismic performance. This study intends to evaluate the overall life-cycle resilience performance and post-seismic loss analysis of bridges equipped with two different isolation systems including lead rubber bearings and friction pendulum bearings. Two different bridge configurations and three different suites of earthquakes representing possible seismic hazards at the bridge site are considered. The comparative resilience assessment and cost analysis represent the base-isolation technique's adequacy, effectiveness and cost-effectiveness. Statistical analysis is conducted to identify the parameters affecting the seismic resiliency, loss and cost analysis of base-isolated bridges. The results show that seismic resilience, loss and cost analysis are more sensitive to the type of ground motions, geometric shape of the bridge and type of isolation bearings, respectively. [ABSTRACT FROM AUTHOR]

Base-isolated building structures prove highly effective in seismic events, particularly when designed using direct displacement-based methods. This design approach ensures that the structure's behavior remains under control during such events. In the present study, 8-, 10-, and 12-story base-isolated RC frame structures were designed using the direct displacement-based design (DDBD) approach. The building was modeled using finite-element software and subjected to a set of ground motion records scaled to different intensity levels. The nonlinear behavior of the RC frame with lead rubber bearing (LRB) was evaluated using incremental dynamic analysis (IDA). The seismic fragility assessment of the base-isolated RC frames was conducted by generating fragility curves from the outcomes obtained through IDA. The probability of exceedance of various damage of base-isolated RC frames designed using the DDBD approach was then compared with the forced-based design (FBD) approach to compute the efficiency of the DDBD approach for base-isolated RC frames. The results indicate that the base-isolated RC frame designed using the DDBD method exhibits good seismic performance with 35.68% less response and a low probability of exceeding collapse. [ABSTRACT FROM AUTHOR]

Several bridges in Indonesia are designed using elastomeric bearing (ERB) with a low capability of reducing seismic responses. This results in a significant demand for larger pier cross-sectional dimensions and a greater number of reinforcements, necessitating the consideration of seismic isolation devices to optimize the pier configuration. Lead rubber bearing (LRB) has been widely used as a seismic isolation device due to the natural period shifting and sufficient energy dissipation, but it costs a lot. A shear panel damper equipped with a gap (SPDG) was proposed regarding its capability to provide high damping at low cost as an alternative device to LRB. This study compared the seismic performance of three structural systems of simply supported prestressed concrete (PSC) box girder bridges. Those were analyzed using Nonlinear Time History Analysis (NLTHA) with the OpenSees software. As a result, both SPDG and LRB increased the structural flexibility and generated similar relative pier responses to the conventional bridge with ERB. For example, SPDG generated the relative responses of the top pier displacement, base shear, and bending moment up to 64.76%, 83.55%, and 65.66%, while LRB was 64.92%, 83.39%, and 66.89%, respectively. Meanwhile, the bridge’s structural performance equipped with LRB and SPDG showed a fully operational and operational limit, while the one with ERB reached the life safety limit due to the longitudinal earthquake. The life safety limit due to the transverse earthquake was also observed in the three bridge models. In conclusion, SPDG is applicable in the seismic isolation system as it has a similar performance to the LRB.

This paper investigates the dynamic response of low-medium-speed (LMS) maglev vehicle moving on the isolated bridge with lead rubber bearings (LRBs). In the vehicle-guideway bridge model, the vehicle is simulated as a 50-degree-of-freedom model consisting of a car-body and ten bogie modules. The guideway bridge with LRB is established by the finite element method, and the guideway is interacted with the vehicle by the actively controlled electromagnetic forces. The LRB is simulated by the nonlinear spring element for reflecting the hysteretic performance, and a fast nonlinear analysis (FNA) method is proposed to achieve the potential nonlinear behavior of LRB under vehicle load. Then, the dynamic response of maglev vehicle running on the isolated bridge with LRB is investigated and compared to that on the non-isolated bridge. The effect of vehicle speed and LRB isolation degree on the coupled system responses is studied. Furthermore, the driving quality of vehicle on LRB bridge is discussed, and the applicability of LRB to maglev line bridge is thoroughly evaluated. The results show that the installation of LRB exhibits relatively insignificant influence on the vertical response of vehicle-guideway system, while could enlarge the lateral response. The lateral response of coupled system is much more vulnerable to the isolation degree, and it is recommended that the isolation degree of LRB should not exceed 2.50 to guarantee the driving comfort and running safety. [ABSTRACT FROM AUTHOR]

The seismic behavior of a partially filled rigid rectangular liquid tank is investigated under short- and long-duration ground motions. A finite element model is developed to analyze the liquid domain by using four-noded quadrilateral elements. The competency of the model is verified with the available results. Parametric studies are conducted for the dynamic parameters of the base-isolated tank, using a lead rubber bearing to evaluate the optimum damping and time period of the isolator. The application of base isolation has reduced the total and impulsive hydrodynamic components of pressure by 80 to 90 percent, and base shear by 15 to 95 percent, depending upon the frequency content and duration of the considered earthquakes. The sloshing amplitude of the base-isolated tank is reduced by 18 to 94 percent for most of the short-duration earthquakes, while it is increased by 17 to 60 percent for the majority of the long-duration earthquakes. Furthermore, resonance studies are carried out through a long-duration harmonic excitation to obtain the dynamic behavior of non-isolated and isolated tanks, using a nonlinear sloshing model. The seismic responses of the base-isolated tank are obtained as higher when the excitation frequency matches the fundamental sloshing frequency rather than the isolator frequency. [ABSTRACT FROM AUTHOR]

Several bridges in Indonesia are designed using elastomeric bearing (ERB) with a low capability of reducing seismic responses. This results in a significant demand for larger pier crosssectional dimensions and a greater number of reinforcements, necessitating the consideration of seismic isolation devices to optimize the pier configuration. Lead rubber bearing (LRB) has been widely used as a seismic isolation device due to the natural period shifting and sufficient energy dissipation, but it costs a lot. A shear panel damper equipped with a gap (SPDG) was proposed regarding its capability to provide high damping at low cost as an alternative device to LRB. This study compared the seismic performance of three structural systems of simply supported prestressed concrete (PSC) box girder bridges. Those were analyzed using Nonlinear Time History Analysis (NLTHA) with the OpenSees software. As a result, both SPDG and LRB increased the structural flexibility and generated similar relative pier responses to the conventional bridge with ERB. For example, SPDG generated the relative responses of the top pier displacement, base shear, and bending moment up to 64.76%, 83.55%, and 65.66%, while LRB was 64.92%, 83.39%, and 66.89%, respectively. Meanwhile, the bridge's structural performance equipped with LRB and SPDG showed a fully operational and operational limit, while the one with ERB reached the life safety limit due to the longitudinal earthquake. The life safety limit due to the transverse earthquake was also observed in the three bridge models. In conclusion, SPDG is applicable in the seismic isolation system as it has a similar performance to the LRB. [ABSTRACT FROM AUTHOR]

Lead rubber bearing (LRB) may be subjected to low temperature effect and superstructure weight when it was used in the cold regions, which will affect the durability of the bearing. To investigate the performance degradation of the LRB under combination of low temperature cycles and superstructure weight, five specimens were designed to conduct 0, 20, 40, 60, 80, and 100 low temperature cycles while maintaining super load of 0, 4, 7, 10, and 12 MPa. The use of ultra low temperature and ordinary temperature room to simulate the environment of low temperature effect and the specimen was kept under compression to simulate superstructure weight. The degradation of the mechanical properties of LRB was analyzed by conducting vertical compression tests and horizontal shear tests on the specimens. The results show that the vertical compression stiffness, equivalent horizontal stiffness, post-yield stiffness, yield force, and equivalent damping ratio of LRB show a decreasing trend under the low temperature cycles and superstructure weight. With the increase of superstructure weight, the degradation of equivalent horizontal stiffness is aggravated, the equivalent damping ratio does not degenerate, and the degradation of post-yield stiffness and yield force is weakened. Finally, the least squares method is used to analyze the change of its horizontal shear performance and give the degeneration curve and degeneration function for 50 years. The degradation curve of the horizontal shear performance of LRB is basically in the form of an exponential function. [ABSTRACT FROM AUTHOR]

Lead rubber bearings (LRBs) are a type of isolation bearing that have a combination of rubber and lead as the main components. These bearings are widely used in bridges, buildings, and other important structures due to their high load‐carrying capacity and excellent energy dissipation capability. However, the behavior of LRBs is complex and nonlinear, making it difficult to predict their behavior and performance under different loading conditions. The objective of this research is to develop a comprehensive analytical model of LRBs that can accurately predict their behavior under low to large levels of strain. The proposed model considers nonlinearity, hysteresis, stiffness, damping, and rate‐dependent behavior of LRBs. The model is also able to consider the effect of temperature on the rubber and lead components of the bearing. The developed model is validated using experimental results and is shown to provide accurate predictions of the LRB response under different strain levels. The accuracy of the developed LRB model is also validated using shake table test results of an LRB‐isolated bridge under low and large strain. This research provides a valuable tool for engineers and designers to predict the behavior and performance of LRBs and optimize their design. [ABSTRACT FROM AUTHOR]

In this study, the maximum isolator displacement (MID), maximum isolator force (MIF), and maximum acceleration (MA) values that occur at the isolation level in seismically isolated structures were investigated using the nonlinear response history analyses (NRHA) by considering four different scaling methods. Both horizontal components of the ground motion records scaled with different scaling methods were applied simultaneously to the isolation unit modeled with lead rubber bearing, and bi-directional analyzes were performed. In the analyses, lead rubber bearings were modeled with two different approaches as the case deterioration due to the heating effect in the lead core is considered (Temperature Included, TI) and the case it is not considered (Boundary Analysis, LB-UB). In the analyses, four different Q/W ratios (0.75, 0.90, 0.105, and 0.120) representing the isolation unit strength, and five different Tiso (2.5s, 2.75s, 3.0s, 3.25s, and 3.5s) representing the isolation period were taken into account. As a result, while the variation in the scaling methods does not create a significant change on the maximum isolator forces, it is observed that it can cause changes up to 25% in the maximum isolator displacements and maximum acceleration values. This differentiation is negligibly affected by how the seismic isolator is modeled. [ABSTRACT FROM AUTHOR]

This study investigates the influence of earthquake duration on seismic fragility of base isolated nuclear power plant (NPP) structures. Two groups of ground motions are employed in performing time history analyses, in which short duration (SD) and long duration (LD) characteristics are considered. The advanced power reactor 1400 (APR1400) NPP structures are used for developing finite element model, which is constructed using lumped-mass stick elements. A series of 486 lead rubber bearings (LRBs) are installed under the base mat of the NPP structures to reduce the seismic damage. Seismic responses of the base isolated NPP are quantified in terms of lateral displacements and hysteretic energy distributions of LRBs. Seismic fragility curves for damage states, which are defined based on the deformation of LRB, are developed. The results reveal that the average lateral displacements of LRBs under SD and LD motions are very similar. For PGA larger than 0.4g, the mean deformation of LRB for LD motions is higher than that for SD motions. The probability of damage of base isolated NPP structures under LD motions is reduced approximately 15% compared to that asubjected to SD earthquakes. This finding emphasizes that it is crucial to use both SD and LD ground motions in seismic evaluations of base isolated NPP structures

Near-fault earthquakes with high amplitude, long-period pulses have a destruction potential for seismically isolated buildings. Since the number of historical near-fault earthquake records is not sufficient for comprehensive studies, synthetic pulse models can be used to simulate these records. The effectiveness of different pulse models has been investigated for seismically isolated structures; however, in these studies lead core heating, which is known to have significant effects in near-fault earthquakes, was not taken into account. In this study, in order to investigate the success of pulse models in determining the seismic response of isolated buildings exhibiting lead core heating under the effect of near-fault earthquakes, nonlinear time history analyses were performed under historical near-fault earthquakes and synthetically produced counterpart ground motion records. The results showed that although general behavior can be determined with pulse models, differences can arise due to lead core heating. [ABSTRACT FROM AUTHOR]

Effects of soil-structure interaction (SSI) on the seismic performance of cylindrical ground-supported liquid storage tanks are studied. The present study attempts to investigate the effects of uncertainties, associated with the critical soil parameters, on the seismic behavior of liquid storage tanks. Random multi-layered soil models coupled with the fixed base liquid storage tank are developed and analyzed. Further, the tank structure is considered base-isolated with lead rubber bearing and analyzed with the same set of soil models, to investigate the seismic behavior of base-isolated tank under uncertain soil condition. A set of three ground motions are selected from a large suite through a mean spectral matching scheme for investigating the effect of soil uncertainties on the seismic response. Distributions of the peak seismic response quantities observed herein show that the uncertainties in soil parameters critically affect the seismic responses of fixed base and base-isolated liquid storage tanks. Sloshing displacement of fixed base and base-isolated tanks is affected by both uncertainty in the soil parameters and ground motion characteristics. Nevertheless, for ground-supported tank, relatively larger dispersion or variability of base shear and overturning moment, as compared to that of the sloshing response, is observed. [ABSTRACT FROM AUTHOR]

The response spectrum method (RSM), specified by the Ministry of Construction notification Vol. 2009, is not part of the countermeasure to address the Nankai trough long‐period and long‐duration ground motions (LPGMs) announced in 2016. Consequently, in this study, an approach was proposed to assess the effect of changes in characteristics due to repeated deformations using the RSM for LPGMs and seismically isolated buildings using lead rubber bearings (LRBs). However, this study identified potential areas for improvement in the calculation of effective damping using the RSM. An effective damping calculation method of the RSM using an effective ductility factor is introduced to enhance the accuracy of the proposed method. The proposed RSM‐based method was verified against the methods based on nonlinear time history analysis. The earthquake response prediction results using the proposed method were compared with those of not only the simplified method but also the precise and the quasi‐precise methods. The accuracy of earthquake response prediction using the proposed approach is increased by 30%–50% when the effective ductility factor is used to compute the effective damping. Therefore, earthquake response can be predicted using the proposed method, and the accuracy achieved is similar to the nonlinear time history analysis. [ABSTRACT FROM AUTHOR]

One of the challenges in real‐time dynamic testing is effectively controlling axial forces for axially stiff members such as columns, walls, and base isolators. Axial force has a significant influence on structural strength and post‐yield behavior, thereby maintaining proper axial force boundary conditions is crucial for accurate seismic performance evaluation. To overcome this challenge, a displacement‐based force control method using the adaptive time series compensator (D‐ATS) was developed in the existing study, but this method requires additional sensors such as displacement transducers and accelerometers to ensure the accuracy of force control. In this study, a new real‐time force control method is introduced, which eliminates the need for additional sensors beyond the default sensors available in a typical servo‐hydraulic actuator. Newly developed modules are also provided, which can satisfactorily estimate the velocity and force change rate of actuator, while effectively mitigating oil‐column resonance. Experimental validation is conducted using lead rubber bearings (LRBs) subjected to axial force and lateral movements. The results demonstrate the exceptional performance of the new force control method, offering a convenient and cost‐effective approach for applying axial forces in real‐time dynamic testing. [ABSTRACT FROM AUTHOR]

This study comprehensively investigates the seismic response of a partially filled rectangular liquid tank equipped with a bottom-mounted submerged block under six real earthquakes of varying frequency contents. Based on a velocity potential theory, Galerkin's method is employed for the liquid domain formulation. A finite element algorithm is developed for the model and the simulated results are validated with the existing solutions. A parametric study is conducted to present the influence of isolator properties on the critical seismic responses. The efficacy of lead rubber bearing is emphasized in the overall dynamic response of the tank–block–isolation systems by varying the location and height of the block. The total and impulsive hydrodynamic pressure of the non-isolated tank decreases when a block is mounted at the base and a subsequent reduction is noticed due to the eccentricity of the block across the tank wall close to the block. Also, the eccentric configuration of the block has shown a typical reduction in the total base shear for most of the earthquake responses when a specific block depth is considered. Furthermore, a significant decrease is noticed in the impulsive and total hydrodynamic pressure and base shear due to the application of lead rubber bearing where the reduction is higher for high-frequency motions and relatively lower for low- and intermediate-frequency content seismic motions. The impulsive response is invariably dominant over the convective one in the overall dynamic responses of different non-isolated tank systems irrespective of the earthquakes whereas the convective response is found to be predominant in the base-isolated tank responses in majority of the earthquakes considered. However, the earthquake's frequency has noticeably influenced the slosh elevation, total base shear and convective base shear responses. [ABSTRACT FROM AUTHOR]

Lead Rubber Bearing (LRB) is a passive type of base isolation that can be used as a damper for earthquake vibrations on bridges and buildings. The components that make up the LRB are several layers of rubber laminated to steel plates to increase vertical rigidity. LRB is also reinforced with lead cores to dissipate earthquake energy that enters the bridge structure or buildings. This paper will explain the design and production of LRB and test the results of the analysis. In this design, the properties of the materials used in the LRB are explained, the function of each material, the relationship between the design and the need to absorb earthquake loads on bridge structures or buildings. It also explains the determination of elastomeric thickness and number of layers, size of insulator, elastomer thickness and number of layers, number of rubber layers, total height, vertical and horizontal stability checks. The production method is very important to get a quality LRB product. Production starts from material selection, vulcanization process and quality control. The research was carried out successfully by studying the literature and technical analysis by carrying out several simulations with various dimensions to get better performance. Several developments were made to get better LRB performance. The damping of structures without base isolation is generally +/- 5%. For the need for good performance against earthquake loads, the attenuation can be increased to 20–30%. This is very useful for reducing earthquake loads, when a decrease in building acceleration cannot be obtained in tall buildings with base isolation. Likewise with the dimensions of the lead core. This research is still limited to theoretical analysis and prototyping, because no experiments have been carried out in the laboratory or applied to a construction project

Abstract The response spectrum method (RSM), specified by the Ministry of Construction notification Vol. 2009, is not part of the countermeasure to address the Nankai trough long‐period and long‐duration ground motions (LPGMs) announced in 2016. Consequently, in this study, an approach was proposed to assess the effect of changes in characteristics due to repeated deformations using the RSM for LPGMs and seismically isolated buildings using lead rubber bearings (LRBs). However, this study identified potential areas for improvement in the calculation of effective damping using the RSM. An effective damping calculation method of the RSM using an effective ductility factor is introduced to enhance the accuracy of the proposed method. The proposed RSM‐based method was verified against the methods based on nonlinear time history analysis. The earthquake response prediction results using the proposed method were compared with those of not only the simplified method but also the precise and the quasi‐precise methods. The accuracy of earthquake response prediction using the proposed approach is increased by 30%–50% when the effective ductility factor is used to compute the effective damping. Therefore, earthquake response can be predicted using the proposed method, and the accuracy achieved is similar to the nonlinear time history analysis.

In order to study the effect of initial shear deformation on the mechanical properties and internal stress of lead rubber bearing under large shear deformation, the finite element model of lead rubber bearing was established based on the support specification parameters provided by the factory, and the correctness of experimental data and finite element model was verified. Then, the influence of different parameters such as bearing size, shape coefficient and vertical pressure on the 100% horizontal performance of lead rubber bearing with initial shear deformation and the maximum stress ratio of internal steel plate rubber were analyzed, and the internal stress of the bearing under large shear strain was analyzed. Compared with no initial shear deformation,the results show that the maximum change of 100% horizontal equivalent stiffness of lead rubber bearing with compressive stress, initial shear deformation and bearing shape coefficient is 5%, and the influence degree is small. The initial shear deformation has a certain influence on the stress of rubber and steel plate under 100% shear strain condition of rubber isolation bearing, but the tensile strength of rubber material and the yield strength of steel plate are basically not reached, and the bearing is in a safe state. The initial shear deformation has a great influence on the stress of rubber and steel plate under the condition of more than 250% shear strain. The stress of rubber or steel plate under different shear strain conditions may reach tensile strength or yield strength of steel plate, and the bearing has a great risk of damage. Through analysis, it is suggested that when the actual shear strain of the support is 400%, 350%, 300%, 250%, 200% and 100%, the initial deformation respectively cannot exceed 0, 20%, 70%, 120%, 170% and 270% . [ABSTRACT FROM AUTHOR]

While collapse mechanisms have received significant attention for conventional buildings, they are less well understood for isolated buildings. Recently, there has been a more concerted effort to quantify the collapse probability of isolated structures; however, the majority of the research has explored the behavior of buildings isolated with concave sliding bearings, also referred to as friction pendulum (FP) bearings. Isolated buildings are expected to perform similarly under defined ground motion levels regardless of the type of bearing used. Yet the collapse probability of isolated buildings is directly dependent on the bearing failure characteristics, which differ by bearing type. Therefore, employing different isolation systems while following the same design guidelines may result in different collapse probabilities. In this study, the collapse probabilities of a 3-story buckling restrained brace frame isolated with either double-concave FP bearings or lead rubber bearings are compared. Different designs at maximum displacement are considered including use of moat walls versus allowing failure of the bearings (or impact of the restraining rims for FP bearings). In the absence of the moat wall, the system-level failure using both bearing types is triggered by exceeding defined displacement capacities. In contrast, with the moat wall, the system-level failure is dominated by either axial component-level failures or excessive yielding of the superstructure. However, when the moat wall limits ultimate displacement, the difference in collapse probabilities is small. [ABSTRACT FROM AUTHOR]

Abstract Elastomeric bearings (EB) and lead-rubber bearings (LRB) are used in bridge structures to reduce vehicle vibrations, wind loads, and earthquakes. Therefore, studying their stability is crucial to ensuring the stability of the bridge system itself. Building upon previously proposed linear and partially nonlinear models, two fully nonlinear models suitable for EBs and LRBs are proposed in this paper. The models are developed to adequately account for the interaction between the horizontal and vertical loads and their effect on the bearing’s performance. This study considers that the horizontal and vertical loads do not always act in isolation and that their interaction can significantly affect the bearing’s overall behavior and stability. Comparisons with experiments demonstrated that the models could accurately replicate the behavior of seismic isolators. Additionally, analytical models are developed to predict the horizontal and vertical stiffnesses as a function of the critical buckling load. The two mathematical models can readily be incorporated into open-source structural analysis software, such as OpenSees.

This study presents a novel self‐centering (SC) base isolation system enabled by traditional lead rubber bearing (LRB) incorporating superelastic shape memory alloy (SMA) U‐shaped dampers (hereinafter referred to as SMA‐LRB). This system is particularly suitable for some important structures (e.g., hospital buildings) that require high seismic performance and rapid recovery of normal serviceability after a severe earthquake. The working mechanism of the SMA‐LRBs is first illustrated, followed by a comparative experimental study on the traditional LRB and the emerging SMA‐LRB. Test results confirm the satisfactory flag‐shaped hysteresis loops of SMA‐LRB associated with significantly reduced residual deformation under cyclic loading. Subsequently, a refined numerical modeling strategy for these bearings is developed. The seismic performances of the SMA‐LRBs are examined systematically through two comparative reinforced concrete (RC) frame buildings, namely, the traditionally isolated and the SC isolated cases under far‐ and near‐field earthquakes. Seismic fragility analyses are further carried out through incremental dynamic analysis (IDA). The seismic responses demonstrate that the SC isolated building can match or improve the behavior of the traditional isolated buildings. Compared with the considerable residual deformation of the traditional isolated system under some earthquake events, the SC isolated system exhibits negligible residual deformation that can significantly avoid normal serviceability disruption while achieving the high‐performance objectives. The SC base isolation system can provide a promising type of advanced seismic protection device for earthquake resilient design. [ABSTRACT FROM AUTHOR]

Isolators and dampers are devices that dissipate energy and reduce the seismic response of structures during strong earthquakes. Lead Rubber Bearings (LRBs) and Tuned Mass Dampers (TMDs) are two common types of these devices. Studying non-linear behavior and seismic properties of structural systems equipped with this type of isolators and dampers can significantly enhance understanding of their behavior against lateral forces caused by strong earthquakes. In this study, a 9-story steel structure was analyzed using the Endurance Time Analysis (ETA) method in SAP2000 software with fixed and isolated bases, along with a tuned mass damper with different mass ratios and without a tuned mass damper. The analysis results indicate that the tuned mass damper is highly effective in reducing the displacement of the isolator level, drift ratio, and story shear forces. This effect is more significant with higher mass ratios of the TMD. This effect is more pronounced with higher mass ratios of the TMD. However, reducing the absolute acceleration response of the structure has not been effective, and increasing the mass ratio of the TMD only reduces the performance of the control system in improving the absolute acceleration response compared to the isolated state. [ABSTRACT FROM AUTHOR]

Recent earthquakes have enforced the engineering community to design seismically more efficient buildings through the energy dissipation systems. For this purpose, this paper investigates the seismic behavior of a high-rise building with a series of base isolation systems. Firstly, a 20-storey steel frame is selected as a fixed-base building, and then equipped with lead rubber bearings (LRBs). In the modelling of LRB, isolation period is alternatively varied as 4, 4.5, and 5 sec to evaluate the effectiveness of the isolator characteristic on the seismic performance of the high-rise base-isolated buildings. The seismic responses of the fixed-base and base-isolated buildings evaluated through a series of time-history analyses are performed using natural ground motion records. The analysis results are compared using engineering demand parameters such as storey displacement, isolator displacement, relative displacement, roof drift, interstorey drift ratio, absolute acceleration, base shear, base moment, input energy, and hysteretic curve. It is revealed that adjusting the isolation period in the design of LRB improved the seismic performance of the base-isolated high-rise steel buildings. [ABSTRACT FROM AUTHOR]

The research on traditional and innovative seismic isolation techniques has grown significantly in recent years, thanks to both experimental and numerical campaigns. As a consequence, practitioners have also started to apply such techniques in real applications, and nowadays, seismic isolation is widespread in regions characterized by a high level of seismic hazard. The present work aims at providing practitioners with very simple procedures for the first design of the isolation devices of a building, according to the most common typologies of isolators: Rubber Bearings, Lead Rubber Bearings and Curved Surface Sliders. Such Fast Design Procedures are based on simplified approaches, and the mechanical properties of the implemented devices can be obtained by assuming a performance point of the overall structural system, namely effective period and equivalent viscous damping. Furthermore, some important parameters are defined, according to the outcomes of a statistical analysis of the test database of the EUCENTRE Foundation in Italy. Finally, results of a validation study have been provided by analyzing a case-study structure through a Multi Degree of Freedom oscillator and a full 3D Finite Element model.

In 2016, a countermeasure was announced against the Nankai Trough long‐period and long‐duration ground motions (LPGMs) in Japan. However, the response spectrum method (RSM), indicated by the Ministry of Construction notification Vol. 2009 (MCN), was out of the countermeasure. An RSM considering characteristic changes due to repeated deformations has also been proposed. However, since the damping correction formula of MCN was used, its applicability to LPMGs has not been sufficiently investigated. In this paper, a method is proposed to evaluate the influence of characteristic changes due to repeated deformations using RSM for LPGMs and seismically isolated buildings using the lead plug‐inserted laminated rubber (LRB). [ABSTRACT FROM AUTHOR]

The Mega-Sub Controlled Structure Systems (MSCSS) with lead rubber bearings (LRBs) is an innovative and attractive vibration control system. This study proposes a method for obtaining the optimal member sizes of the MSCSS with LRBs under non-stationary stochastic ground motions. Based on the structural characteristics of the MSCSS with LRBs, this study puts forward the "optimal criteria method with two-stage equal reliability." The probability density evolution theory is used for the dynamic reliability analysis of the MSCSS with LRBs, and a MATLAB program is written for the member size optimization. A finite element model with four mega-floors and 32 sub-floors is studied as an example. The reliability and seismic response of the model before and after optimization are compared. The optimization eliminates the "weak floors" in the structure so that the reliability distribution after optimization is more uniform than before, and the seismic performance of the structure is also improved. [ABSTRACT FROM AUTHOR]

Lead Rubber Bearings (LRBs) represent one of the most widely employed devices for the seismic protection of structures. However, the effectiveness of the same in the case of curved bridges has not been judged well because of the complexity involved in curved bridges, especially in controlling torsional moments. This study investigates the performance of an LRB-isolated horizontally curved continuous bridge under various seismic loadings. The effectiveness of LRBs on the bridge response control was determined by considering various aspects, such as the changes in ground motion characteristics, multidirectional effects, the degree of seismic motion, and the variation of incident angles. Three recorded ground motions were considered in this study, representing historical earthquakes with near-field, far-field, and forward directivity effects. The effectiveness of the bi-directional behavior considering the interaction effect of the bearing and pier was also studied. The finite element method was adopted. A sensitivity study of the bridge response related to the bearing design parameters was carried out for the considered ground motions. The importance of non-linearity and critical design parameters of LRBs were assessed. It was found that LRBs resulted in a significant increase in deck displacement for Turkey ground motion, which might be due to the forward directivity effect. The bi-directional effect is crucial for the curved bridge as it enhances the displacement significantly compared to uni-directional motion. [ABSTRACT FROM AUTHOR]

Base isolation of buildings is the most efficient way of designing seismically resistant structures. Application of seismic isolators allows mutually independent movements of the ground and the structure during earthquakes. The application of seismic isolators increases the natural period of vibrations, which reduces the seismic forces in the structure. The paper analyzes the influence of the application of lead rubber bearings on the response of the structure to the action of an earthquake. A reinforced concrete frame structure was analyzed both for the case of base isolation and rigid foundation. Based on the comparative analysis of the natural period of vibrations, base shear seismic forces, displacement of the top level of the structure and relative inter-storey drift, conclusions were drawn about the efficiency of application of this type of seismic isolator. The required amount of ductility of a structure, as well as damage to structural and non-structural elements, is greatly reduced by base isolation.

Abstract In 2016, a countermeasure was announced against the Nankai Trough long‐period and long‐duration ground motions (LPGMs) in Japan. However, the response spectrum method (RSM), indicated by the Ministry of Construction notification Vol. 2009 (MCN), was out of the countermeasure. An RSM considering characteristic changes due to repeated deformations has also been proposed. However, since the damping correction formula of MCN was used, its applicability to LPMGs has not been sufficiently investigated. In this paper, a method is proposed to evaluate the influence of characteristic changes due to repeated deformations using RSM for LPGMs and seismically isolated buildings using the lead plug‐inserted laminated rubber (LRB).