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Seismic intensity measures (IMs) quantify the severity of ground motions and their impacts on structures. They play a vital role in many aspects of earthquake engineering. This paper proposes a novel method, namely the express iteration method (EIM), for constructing effective vector-valued IMs based on dozens of existing scalar ones given a specific engineering structure or a class of them. Taking advantage of the sophisticated while efficient mapping between scalar IMs and engineering demand parameters (EDPs) via a machine learning model, EIM iteratively eliminates less important scalar IMs from a pool of candidates to find the most effective combinations for a vector-valued IM and achieves superior computational efficiency by avoiding updating the nonlinear mapping during the process. Taking a base-isolated structure and its non-isolated counterpart for a demonstrating case study, the performance of the vector-valued IMs determined by EIM is compared with those by other existing methods in the literature for the task of selecting the most unfavorable ground motions. The results show that EIM prioritizes records with the largest peak inter-story drift PIDs and thus leads to the smallest subset that imposes most severe structural damage, while its computational cost was two orders of magnitude smaller as compared to the existing methods of similar effectiveness. Such superior performance can also be expected in all tasks that involve vector-valued IMs, including but not limited to multi-dimensional fragility analysis, incremental dynamic analysis, and real-time seismic damage prediction. [ABSTRACT FROM AUTHOR]

Base isolators, traditionally made from natural rubber reinforced with steel sheets (SERIs), mitigate energy during seismic events, but their use in developing countries has been limited due to high cost and weight. To make them more accessible, lighter, cost-effective reinforcement fibers have been utilized. Additionally, the increasing use of natural rubber has caused waste storage and disposal issues, contributing to environmental pollution and disease spread. Exploring recycled rubber matrices as alternatives, this study improves seismic isolators' mechanical properties through modified reinforcements and layer adhesion. Eight reinforcement materials and eight adhesives, which may be activated with or without heat application, are systematically evaluated. Employing the chosen reinforcements and adhesives, prototypes are tested mechanically to examine their vertical and horizontal performance through cyclic compression and cyclic shear testing. Two innovative devices using recycled rubber matrices were developed, one using a layering technique and another through a monolithic approach shaped with heat and pressure. Both integrate a fiberglass mesh reinforced with epoxy resin; one employs a heat-activated hybrid adhesive, while the other uses a cold bonding adhesive. These prototypes exhibit potential in advancing seismic isolation technology for low-rise buildings in developing countries, highlighting the viability of recycled materials in critical structural applications. [ABSTRACT FROM AUTHOR]

Over the past few decades, the concept of base isolation has gained prominence as a prospective methodology for safeguarding structures against severe seismic events and wind forces. Many international building codes have recognized its effectiveness and incorporated relevant sections. This paper aims to demonstrate the exceptional performance of Lead Rubber Bearing (LRB) isolation systems through an extensive parametric study. The study showcases a significant reduction in various response parameters and emphasizes the substantial energy dissipation capabilities of the LRB system. These compelling results underscore the urgent need to develop a novel design methodology for isolated buildings in alignment with Algerian seismic regulations, which currently lack provisions for this advanced technique. The research introduces an innovative approach for LRB isolators, employing the equivalent static method. This technique is characterized by its utilization of an iterative procedure for adjusting the isolator's displacement in accordance with the mechanical and geometric attributes of the structure. To validate the proposed model, a comprehensive parametric study was conducted on a building designed in compliance with several international codes, including IBC 2000, Italian, Chinese, Japanese, Taiwanese, and Algerian codes. The results stemming from this innovative design methodology closely align with the requirements of these international codes, affirming its global applicability and relevance. [ABSTRACT FROM AUTHOR]

Seismic isolation technology has been extensively used in long-span spatial structures to alleviate losses caused by earthquake disasters. However, limited experimental studies have been conducted to examine the impact of horizontal and vertical vibrations in long-span roof structures with rubber bearings as isolation layers on the isolation effect. This paper presents a study that carried out shaking table experiments on 1/40 scale long-span steel frames, both with and without base isolation. It explores the interplay of horizontal and vertical vibrations in long-span roof structures equipped with rubber bearings, and its influence on the isolation effect. Three ground motions, including horizontal bidirectional (2D) and bidirectional-plus-vertical (3D) components were used as the seismic excitations. The whole structural dynamic responses of the base-isolation (BI) model and fixed-base (FB) model, the local responses of the grids and isolation bearings were measured. Under 2D seismic excitation, the grid layer in the FB model exhibits a substantial vertical acceleration response. When exposed to 3D seismic activity, the isolation system successfully delivers its expected isolation outcome. Although the isolation bearings could not attenuate the vertical seismic acceleration response induced by vertical ground motion, they effectively reduced the vertical dynamic response generated by the coupling by suppressing the horizontal seismic response. [ABSTRACT FROM AUTHOR]

With the shortage of land resources, the engineering application of large height-width ratio liquid storage structure is of great significance. 3-D numerical calculation models of large height-width ratio liquid storage structure are established by ANSYS. The elements Solid 65 and Solid 185 are used to simulate the concrete and the bearing, while the element Fluid 80 is used to simulate the liquid. The dynamic responses of four types of structure are comparatively investigated, which are non-isolated structure with double baffles, isolated structure with double baffles, non-isolated structure with triple baffles and isolated structure with triple baffles. The results show that under the Tianjin waves, the wall tensile stress of the non-isolated structure with triple baffles is decreased by 50% compared to the non-isolated structure with double baffles, while the wall tensile stresses of the isolated structures with double and triple baffles are increased by 10% and 122%, respectively, compared to those of the non-isolated structures. It is shown that conventional rubber isolation is not suitable for the large height-width ratio liquid storage structures with baffles, where the load-bearing capacity and safety of the structure can be improved by increasing the number of horizontal baffles. [ABSTRACT FROM AUTHOR]

Near-fault ground motions with high acceleration peaks and long-period velocity pulses pose a serious threat to the reliability of engineering structures. To reduce the displacement of isolation layer and improve the seismic performance of superstructure under the near-fault ground motions, a composite isolation system, which is composed of friction pendulum system (FPS) and inerter system, namely FPIS, was used in this paper. Based on D'Alembert's principle, the nonlinear motion equations of a base-isolated structure with FPIS were established. The damping effect of two different mechanical layouts of FPIS subsystems, i.e, series-parallel inerter system-I-FPS(SPIS-I-FPS) or series-parallel inerter system-II-FPS(SPIS-II-FPS), were investigated in this study. The strong nonlinearity of FPIS was considered, and the inerter system parameters were designed based on the principle of maximum damping enhancement. The fourth-order Runge-Kutta approach was used to solve the dynamic response of a multi-degree-of-freedom system under seismic excitations. The effectiveness of FPIS was verified by comparing the isolation layer displacement and the acceleration of superstructure calculated by MATLAB with the friction pendulum system and viscous damper (FPS-VD). The nonlinear time history analysis results indicate that within a certain additional damping range, the SPIS-I-FPS subsystem performs effectively than SPIS-II-FPS in reducing the superstructure acceleration and isolation layer displacement. To increase the energy dissipation efficiency of structures, it is recommended to increase the design parameters of the inerter system and control the friction coefficient of FPS within the range of 0.05∼0.10. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Southeast University / Dongnan Daxue Xuebao is the property of Journal of Southeast University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study evaluates seismic mitigation methods, including high damping rubber bearing, lead rubber bearing, double sliding pendulum (DSP), and tuned mass damper (TMD), considering earthquake intensity, building height, and isolation level. Moreover, the study delves into a novel approach that incorporates multi-level isolation and multi-level TMD. Reinforced concrete buildings, ranging in height from 4 to 40 storeys, were nalysed and nalysed using SAP2000 under the seismic influence of the Badra, El Centro, and Northridge earthquakes. The study reveals a significant rise in the fundamental period (T) with base isolation systems, reaching 378% of the fixed base value for a six-storey building. Building height directly affects T values, with simplified equations introduced for calculation. DSP proves 5% more efficient in reducing base shear (BS), while TMD is effective in weaker earthquakes for minimizing lateral displacement. Base isolators outperform mid-level isolation and TMD at the top storey. Combining base isolators with TMD at the top storey is deemed impractical and uneconomical. The study recommends multilevel isolation or multilevel TMD for enhanced seismic isolation efficiency, with four-level isolation achieving an 80% reduction in BS for 12-storey buildings. In addition, four-level TMD outperforms TMD at the top storey with a 44.5% reduction in BS, surpassing the 26.6% reduction achieved with TMD at the top storey only.

Growing concerns about seismic events enforced structural engineers and architects to embrace the hazardous effect of ground motion in design. To address this, researchers have developed various base isolation (BI) techniques. This study comprehensively reviews BI system types, techniques, and implementation. Exploring the dynamic response of three-dimensional BI devices and the mutual effects of isolation devices and soil-structure interaction during strong ground motion, the paper covers topics such as seismic isolation of nuclear power plants, cost analysis, and various optimization techniques. Furthermore, the paper investigates the behavior of isolation devices in beyond-design events, including blast and aircraft impact loading. In general, the seismic isolation and control device response is demonstrated through shaking table tests and computational analysis. The study sheds light on the functions of seismic isolation system by comparing them with fixed base structures. Additionally, the paper presents codal recommendations, recent advancements, and current practices, aligning them with historical developments and past reviews of different BI techniques, along with their advantages and disadvantages. In conclusion, the closing remarks emphasize the future research prospects in this field. [ABSTRACT FROM AUTHOR]

In this paper, the effectiveness of seismic isolation using lead rubber bearings (LRBs) and friction pendulum systems (FPSs) for slender and broad, grounded and elevated tanks (two seat locations of isolation systems in elevated tanks) is investigated under bi-directional excitation of up to 10 records of earthquakes. An analytical mechanical model for a flexible, concrete cylindrical tank, taking into consideration the effect of wall mass and sloshing, is used. The assumptions underlying the mechanical model are basic equations of the motion according to the theory of fluid dynamics. So, the assumptions are more realistic and the results therefore are more accurate than the previous models. The results show that by selecting the best mechanical properties of base isolation systems, reductions of seismic base shear in the grounded broad tanks are around 35% and 30% and for the grounded slender tanks are around 55% and 58% in the x- and y-directions, respectively. Maximum total hydrodynamic pressure is reduced considerably by about 40% on average in all grounded and elevated models. As a result of isolation, elevated tanks are concluded to be better candidates in terms of more effective application of seismic isolation. [ABSTRACT FROM AUTHOR]

Elastomeric isolation bearings exhibit complex coupled horizontal-vertical behavior. Most existing macroscopic models simulate the quasistatic test results well but have deficiencies in simulating the dynamic behavior of bearings. In this paper, the experimental observations of previous dynamic bearing tests were investigated. The simulation capacity of existing macroscopic models was checked by comparison with the test data. The results show that the calculated axial load and hysteresis loops exhibit undesired oscillations under dynamic excitation. The intrinsic deficiency of existing models in simulating the dynamic response of a bearing was identified as the coupling or off-diagonal terms in the tangent stiffness matrix and the variation of vertical stiffness of the model. Motivated from this key observation, a new macroscopic model was developed to account for the dynamic behavior of bearings, followed by the suggestion of its numerical implementation. Through the introduction of a new axial load expression, the tangent stiffness matrix of the new model was semidecoupled, and the vertical stiffness of the new model remains unchanged, which reduced the interaction between the horizontal and vertical behavior. The simulation capacity of the new model was then validated by comparison with previous test data. The results show that the new model effectively captures the axial load variation and hysteresis loop of the bearings under dynamic excitations. Moreover, it was found that the consideration of the bearing height improved the simulation accuracy, and the size effect of the bearing is critical for isolated structures with large bearing-to-superstructure-height ratio, such as low- to medium-span bridges. [ABSTRACT FROM AUTHOR]

This study focuses on the design procedure and development of the unbonded fiber-reinforced elastomeric isolator (UFREI) and its application to prevalent masonry building practices in developing countries. The proposed design procedure caters to the development of rectangular UFREIs with or without modifications, considering an improved shear behavior formulation. Afterward, the proposed design procedure is used to design the isolation system for a pre-existing base-isolated masonry building located in the Tawang district in the northeastern state of Arunachal Pradesh in India. Three different configurations of the above building [i.e., fixed base, isolated using square UFREIs, and isolated using modified rectangular UFREIs (MR-UFREI)] are considered for a comparative response analysis under a set of probable ground motions during a service period of 100 years. The building is modeled in SAP2000, where it is subjected to nonlinear time-history analysis under the considered set of ground motions. The masonry walls are modeled as nonlinear layered shell elements, and concrete floors as rigid diaphragms. An improved shear formulation of UFREI is used to model the isolation system as a combination of a multilinear elastic spring and a dashpot. Major response parameters, i.e., floor accelerations, isolator displacement, interstory drift ratio, etc., are investigated, and a significant improvement is witnessed throughout with the use of the MR-UFREI isolation system. The stress–strain distribution and concentrations in the masonry structure and isolation system are also investigated. These distributions are further used to quantify the fatigue losses to the elastomer layers used in the isolation system during the design period, which is found to be minimal. [ABSTRACT FROM AUTHOR]

The dynamic behavior of a pile-supported structure with a base isolator was investigated by using 1 g shaking table model tests considering soil–structure interaction (SSI). The emphasis was placed on evaluating the effect of the with/without developed base isolator on the dynamic behavior of end-bearing piles and structures. The experiment was performed through sweep tests and sinusoidal wave tests. As a result of the tests, the developed base isolator was found to effectively reduce the structure's resonant frequencies and damped the response acceleration under resonance frequencies. According to sweep tests, the base shear force of the pile-supported structure system tends to decrease as the relative density of the soil increases during resonance. It showed that the base isolator tends to reduce significantly the response acceleration of not only the rigid-based structure but also the pile-supported structure. It was shown that although the isolated superstructure recorded large horizontal displacements, piles experienced reduced horizontal displacement and bending moments, regardless of soil conditions. [ABSTRACT FROM AUTHOR]

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Approaches to isolating the base have become a crucial element in enhancing quality stability during a seismic earthquake load. In the present day, base detachment is routinely utilized as an essential arrangement technique for structures and frameworks in seismically active zones. This paper aims towards the dynamic analysis of a multi-story RCC building with various parameters. For the sake of study and verification, a model of a ten-story RCC building with a symmetrical floor plan is considered. The study was conducted using SAP 2000's time-history-based software. In this paper,72 models were studied based on various parameters such as bay width, number of bays, number of floors, and various isolators (Lead Rubber Bearings, Friction Pendulum Bearing, Fixed, and Hinge). The reaction of the structure, for example, time period, base shear, and story displacements are studied and a comparison is made. The paper showed the clear superiority of isolation methods in resisting earthquakes. The friction pendulum support has been the preferred type due to the lowest drift story of the building when it was compared with other support systems. Also, as the results showed a high time period when using the lead rubber bearings, which shows the model's ability to withstand earthquakes.

The stochastic response of multi-story buildings isolated by laminated rubber bearing (LRB), lead-rubber bearing (N-Z system), friction pendulum system (FPS), and resilient-friction base isolator (R-FBI) is investigated under the independent multi-hazard scenario of earthquake ground motion (EQGM), wind load (WL), and blast-induced ground motion (BIGM), which are considered as uncertain inputs. A polynomial regression-based Monte Carlo simulation (PRBMCS) is proposed to enable computationally efficient fragility assessment of base-isolated buildings. The suitability of the PRBMCS for stochastic assessment of the base-isolated buildings is compared with the conventional Monte Carlo simulation (MCS), response surface method (RSM) and Cloud analysis. The fragility curves obtained using the PRBMCS are in good agreement with that of the MCS relatively. The study includes: the effects of the characteristic parameters of the four base isolators on the fragility of the base-isolated buildings under the three hazards; influence of the extent of uncertainty in the excitations; and comparison of fragilities of the base-isolated and fixed-base buildings. Notably, the influences of characteristic parameters of the isolators on the fragility of the base-isolated buildings are different under the three hazards. The differences in the stochastic behaviour under the different hazards could have contradictory influences on the selection of isolation parameters. [ABSTRACT FROM AUTHOR]

This paper focuses on the ultimate state of three‐story wood dwellings with high aspect ratios, which are increasing in Japan's urban areas. Using shaking table test results from the 2019 full‐scale shaking table test, a comprehensive study is conducted on the accuracy of evaluating ultimate state through the story shear failure mode at the first story, the tension fracture mode at the wall base of the first story, and foundation sliding mode on the soil. Methods evaluating the dynamic response behaviors of the building systems are also investigated. In the test, the current Japanese seismic design guidelines were applied, and two Grade‐3 buildings were prepared. One adopted the Post‐and‐Beam structure (A‐building), and the other the Shear‐Wall structure (B‐building). A series of tests planned very different physical boundary conditions surrounding their reinforced concrete (RC) mat foundations. The sills, column bases and wall bases of the upper wood structures were anchored to the RC foundations by steel anchor bolts, according to the current Allowable Stress Design (ASD) requirements. In the first stage, A‐building equipped a Base‐Isolation system, while B‐building represented a generic foundation constructed on a 1.5 m‐height real soil ground by preparing a rigid soil box (Foundation‐Soil system). In the second stage of A‐building and B‐building, the foundation was firmly fixed (Fixed‐Foundation system), and shaking table motions were fully applied to the foundations. The entire test system was setup on the large shaking table facility at E‐Defense, and a series of tests were conducted using JMA‐Kobe motion and JR‐Takatori motion recorded in the 1995 Kobe earthquake as Maximum‐Considered‐Earthquake motions. Confirmed was the change in the structural mechanism due to the upper structural systems and the foundation boundaries. Regarding the upper wood structure performance in the Fixed‐Foundation system, a story shear failure mode was observed at the first story in A‐building, while a tension fracture mode at the base of the first story in B‐building. This difference of failure mode is difficult to determine with ASD. The maximum strength were more than four times higher than the ASD base shear force. Tension fracture capacity at the wall base was mainly enhanced by the presence of the steel anchor bolts. Regarding the foundation performance in Foundation‐Soil system of B‐building, a horizontal displacement up to 240 mm was observed between the foundation and soil when JMA‐Kobe 100% was applied. A response reduction effect was observed in the upper wood structure, similar to the Base‐Isolation system of A‐building. The initial friction and cyclic friction strength capacities between the foundation and soil were quantitatively evaluated considering the horizontal two‐directional sliding. The representative test results were converted to the corresponding SDOF systems based on the first mode response assessment. In the Fixed‐Foundation system, the dynamic response characteristics of the upper wood structures were properly represented using Ibarra‐Medina‐Krawinkler pinching model in the equivalent SDOF system. [ABSTRACT FROM AUTHOR]

Base isolators used in buildings provide both a good acceleration reduction and structural vibration control structures. The base isolators may lose their damping capacity over time due to environmental or dynamic effects. This deterioration of them requires the determination of the maintenance and repair needs and is important for the long-term isolator life. In this study, an artificial intelligence prediction model has been developed to determine the damage and maintenance-repair requirements of isolators as a result of environmental effects and dynamic factors over time. With the developed model, the required damping capacity of the isolator structure was estimated and compared with the previously placed isolator capacity, and the decrease in the damping property was tried to be determined. For this purpose, a data set was created by collecting the behavior of structures with single degrees of freedom (SDOF), different stiffness, damping ratio and natural period isolated from the foundation under far fault earthquakes. The data is divided into 5 different damping classes varying between 10% and 50%. Machine learning model was trained in damping classes with the data on the structure's response to random seismic vibrations. As a result of the isolator behavior under randomly selected earthquakes, the recorded motion and structural acceleration of the structure against any seismic vibration were examined, and the decrease in the damping capacity was estimated on a class basis. The performance loss of the isolators, which are separated according to their damping properties, has been tried to be determined, and the reductions in the amounts to be taken into account have been determined by class. In the developed prediction model, using various supervised machine learning classification algorithms, the classification algorithm providing the highest precision for the model has been decided. When the results are examined, it has been determined that the damping of the isolator structure with the machine learning method is predicted successfully at a level exceeding 96%, and it is an effective method in deciding whether there is a decrease in the damping capacity. [ABSTRACT FROM AUTHOR]

Base isolation proves to be an effective vibration control strategy for buildings. However, the base-isolation floor (BIF) may undergo substantial displacements. To improve the seismic performance of base-isolation system, this paper proposes a multi-performance economical optimization procedure (MPEOP) for exploring the optimal parameters of base isolation system with tuned inerter negative stiffness damper (BIS-TINSD) subjected to non-stationary seismic excitation. The simplified analysis model for BIS-TINSD is developed, followed by the formulation of the state-space representation. The non-stationary seismic excitation is represented as a stationary Gaussian process with a time-modulating function based on the Clough–Penzien spectrum, and combining the equations of motion with seismic excitation results in the augmented state-space representation of structure-damper-excitation, followed by the formulation of differential Lyapunov equation. The multi-objective performance economical index is proposed, in which the performance optimization objective is defined as a weighted combination of base isolation floor displacement and superstructure acceleration, and the economic optimization objective is set as the support stiffness. The Pareto optimal fronts (POF) are adopted to deal with optimal objectives. The examination of optimal design parameters is extended under real earthquake records. The results demonstrate the effectiveness of the MPEOP, and indicate the advantages of the BIS-TINSD compared with the inerter amplify damper (IAD) and negative stiffness inerter damper (NSID). [ABSTRACT FROM AUTHOR]

This study examines the impact of Soil-Structure Interaction (SSI) on the response of seismic-isolated buildings. Reinforced concrete office buildings with different heights are studied. The High Damping Rubber Bearing (HDRB), Lead Rubber Bearing (LRB) and Double Sliding Pendulum (DSP) isolators are utilized to isolate the buildings base. Also, Tunned Mass Damper (TMD) is implemented at top of buildings to improve building response. Soft, medium and hard soils are modelled using direct and substructure approaches. On the other hand, the influence of foundation type on buildings response is examined. The results indicate that considering SSI in soft soil reduces base shear of 6-storey building by 30%, but increases top storey displacement from 128 mm to 182 mm. It is found that base isolators are more efficient in reducing base shear (41-66%) than TMD (10-25%). Simple equations are suggested to calculate the fundamental period based on building height. The soil layer near the foundation, around 75% of the building height, primarily determines the building's response. Therefore, soil investigation can be restricted to a maximum depth of 75% of the building height. Finally, it is found that using pile foundation in soft soil alters building response to resemble that in hard soil conditions. [ABSTRACT FROM AUTHOR]

This study investigates the feasibility of utilizing the friction pendulum system based inter-storey isolation (FPS-I) strategy to replace the friction pendulum system base isolation (FPS-B) for high-rise structures' vibration control against earthquakes. Both experimental verifications and computational analysis are carried out. A scaled nine-storey experimental model structure is constructed in accordance with the third generation Benchmark problem, and three aspects variant FPS with different slideway radius configurations are designed and manufactured based on the geometric similarity criterion. To assess the dynamic characteristics of FPS-B structure and FPS-I structure, four typical ground motions and four different intensities of peak ground acceleration (PGA) are considered. The findings show that FPS-I can effectively suppress the superstructure's acceleration as well as affecting the lower substructure's response. When the same earthquakes occur, the vibration reduction effect of FPS-I strategy is achievable between 50 and 60%, which is obviously superior to FPS-B scheme. The FPS-I technology is observed to have an even greater effectiveness on the entire structure's vibration reduction during strong earthquakes than the traditional FPS-B technology. The basic mode as well as the higher-order mode responses of the high-rise structure can be controlled, resulting in the seismic response of the entire FPS-I structure at lower levels. The first-order mode contributes the most to the superstructure's floor acceleration response. The location of the isolation layer changes the dynamic characteristics of the structure substantially. Finally, the finite element models for FPS-B structure and FPS-I structure are developed. It is demonstrated through the mutual comparison of experimental and numerical results that the finite element model is sufficient accurate for parametric studies. The numerical model can reproduce the dynamic characteristics of both isolation strategies with high fidelity. This research emerges the benefits of FPS with inter-storey isolation to address the issue of high-rise structures being prone to be over turned in the case of base isolation. [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]

Seismic isolation technology makes buildings more capable of withstanding earthquakes, protecting them from major damages or collapse. The same methods of analyses are not suitable for all types of buildings. The isolation system used Armenia, unlike foreign countries ones, cannot take any tension forces since the system doesn't have structural connections to superstructure and substructure of a building. The consequence of this fact can be the occurrence of additional stresses after the redistribution of axial forces in rubber base isolations in high-rise buildings during a seismic action. The stress-strain state analyses of rubber base seismic isolation systems in reinforced concrete dual frame-wall buildings with application of a finite element method carried out in the manuscript. An increase of the stresses during seismic action is discussed and investigated using both Fast-nonlinear time history analysis (FNTHA) and Direct-integration nonlinear time-history analysis (DINTHA). Analysis of the results of the study shows that the axial forces after their redistribution during horizontal earthquake loads in most seismic isolators of high-rise building do not exceed 8%, but for some isolators this difference varies within the range of 12-18% . Taking into account the vertical component, the difference does not exceed 20%, with the exception of three isolators, where it can reach up to 23% . An average increase of the compressive axial forces in the seismic isolation bearing systems of the tall building as a result of redistribution can be taken about 10% . In this case, the displacements and the axial forces of the seismic isolators during analysis of their bearing capacity must be considered simultaneously, but not separately from each other. [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]

In this paper, the effect of seismic pounding of adjacent structures on buildings isolated by double (DFPB) and triple friction pendulum bearings (TFPB) is investigated. The seismic gaps between buildings are calculated based on the Instruction for Seismic Rehabilitation of Existing Buildings, standard No. 360 of Iran, which is not considered for friction pendulum bearings in the previous studies. To this end, a three-dimensional single-story building model is created in the MATHLAB program considering two scenarios including the case without pounding and the case with it. In addition, fifteen different TFPBs and six DFPBs are utilized as seismic isolators to cover a wide range of fundamental periods of the isolation system. Finally, nonlinear time history analyses with seven pairs of ground motion records are conducted to obtain some of the seismic responses of buildings including base shear, drift, story acceleration and maximum displacement of the isolation system. The results show that the seismic pounding considerably increases responses of base-isolated buildings. For example, the floor acceleration and the drift ratio of isolated building with TFPB increased 2 and 6 fold because of seismic pounding. It shows that the seismic gaps calculated by the formula of standard No. 360 may not be sufficient to prevent severe seismic poundings and increase of seismic responses.

Base isolators, traditionally made from natural rubber reinforced with steel sheets (SERIs), mitigate energy during seismic events, but their use in developing countries has been limited due to high cost and weight. To make them more accessible, lighter, cost-effective reinforcement fibers have been utilized. Additionally, the increasing use of natural rubber has caused waste storage and disposal issues, contributing to environmental pollution and disease spread. Exploring recycled rubber matrices as alternatives, this study improves seismic isolators’ mechanical properties through modified reinforcements and layer adhesion. Eight reinforcement materials and eight adhesives, which may be activated with or without heat application, are systematically evaluated. Employing the chosen reinforcements and adhesives, prototypes are tested mechanically to examine their vertical and horizontal performance through cyclic compression and cyclic shear testing. Two innovative devices using recycled rubber matrices were developed, one using a layering technique and another through a monolithic approach shaped with heat and pressure. Both integrate a fiberglass mesh reinforced with epoxy resin; one employs a heat-activated hybrid adhesive, while the other uses a cold bonding adhesive. These prototypes exhibit potential in advancing seismic isolation technology for low-rise buildings in developing countries, highlighting the viability of recycled materials in critical structural applications.

Featured Application: The results can be applicable to the plant equipment design for seismic enhancement. The purpose of this paper is to analyze the seismic response effect caused by the mass eccentricity of individual equipment when conducting base isolation for the improvement of the seismic performance of a nuclear power plant. Recent research has interpreted and confirmed through analysis and testing that base isolation for safety-related equipment in nuclear power plants is an efficient alternative to designing for excessive seismic loads. Depending on the equipment, unavoidable mass eccentricity can occur, which necessitates verification of the response impact caused by eccentricity. In this paper, we analyze the seismic response impact of equipment with mass eccentricity using small base isolators. To do so, sensitivity analysis of the seismic response due to mass eccentricity is conducted for a base-isolated concentrated mass model. Furthermore, three efficient mass eccentricity models suitable for testing are designed and manufactured. Simulation analyses using the finite element method (FEM) models are performed, followed by three-axis shake table tests to validate the seismic response impact of mass eccentricity. In conclusion, it is confirmed that applying small base isolators to equipment with mass eccentricity can affect seismic response impact to some extent when compared for a beyond-design-basis earthquake (BDBE). [ABSTRACT FROM AUTHOR]

In this paper, the effect of seismic pounding of adjacent structures on buildings isolated by double (DFPB) and triple friction pendulum bearings (TFPB) is investigated. The seismic gaps between buildings are calculated based on the Instruction for Seismic Rehabilitation of Existing Buildings, standard No. 360 of Iran, which is not considered for friction pendulum bearings in the previous studies. To this end, a threedimensional single-story building model is created in the MATHLAB program considering two scenarios including the case without pounding and the case with it. In addition, fifteen different TFPBs and six DFPBs are utilized as seismic isolators to cover a wide range of fundamental periods of the isolation system. Finally, nonlinear time history analyses with seven pairs of ground motion records are conducted to obtain some of the seismic responses of buildings including base shear, drift, story acceleration and maximum displacement of the isolation system. The results show that the seismic pounding considerably increases responses of base-isolated buildings. For example, the floor acceleration and the drift ratio of isolated building with TFPB increased 2 and 6 fold because of seismic pounding. It shows that the seismic gaps calculated by the formula of standard No. 360 may not be sufficient to prevent severe seismic poundings and increase of seismic responses. [ABSTRACT FROM AUTHOR]

Introduction: This paper proposes an optimal active vibration control system to control an active tuned mass damper (ATMD), which can help reduce the seismic structural damages caused by the earthquake effects. Methods: The proposed controller exploits the features of the fractional-order calculus to improve the performances of the derivative and the integral actions of the conventional PID controller, the parameters gains ( K p , K i , K d ), λ and μ of the fractional-order PID controller (FO-PID) are selected optimally using the recent artificial hummingbird algorithm (AHA), A comparative study conducted against the classical PID controller in different earthquake excitations, to highlight the advantages of proposed FO-PID. Finally, A new graphical user interface (GUI) based on MATLAB called "SVCS Structural Vibration Control Simulator" is developed to facilitate the simulation of different vibration control systems using different earthquake excitations. Conclusion: The results obtained reflect that using FO-PID controller improves the performance of active control and can reduce further the structural response. [ABSTRACT FROM AUTHOR]

The behavior of isolated integral bridges at the pier (IBP) is scantly reported in the literature. Herein, its behavior is studied in distinction with the isolated conventional bridge under multi-component far and near-field earthquakes. Nonlinear time-history analysis of isolated and corresponding fixed-base bridges having the same geometry is conducted. The response reduction of isolated bridges compared to fixed-base bridges is used as an index to characterize the relative performance of the isolated IBP. The study shows isolating IBP provides greater response reduction and greater protection against damage measured in terms of the maximum plastic hinge rotations that occur in the bridges. [ABSTRACT FROM AUTHOR]