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High damping rubber bearings have been in use for seismic isolation of buildings worldwide for almost 30 years now. In the present work, a brief introduction to the process leading to their manufacturing is first given. Next, a series of novel 1D mechanical models for high damping rubber bearings is proposed, based on the combination of simple and well-known rheological models. These models are calibrated against a set of harmonic tests at strain amplitudes up to 200%. Extension of the models to bidirectional horizontal motion and to time-varying vertical loads is the subject of ongoing work
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... In recent years, rubber isolation bearings have undergone new changes and developments. Considerable efforts have been invested in the development of new rubber isolation bearings [10][11][12][13][14][15][16][17][18]. Compared to ordinary natural rubber isolation bearings and lead-core rubber isolation bearings, high-damping rubber isolation bearings ( Figure 3) have plenty of advantages over the both, such as a simple structure, stable mechanical performance, strong energy dissipation capacity, large stiffness before yielding, environmental protection, etc., that make it an excellent choice for base-isolated structures [16]. ...
... Cross-section of high-damping rubber isolation bearing[13]. ...
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At present, high-damping rubber materials, widely used in the field of engineering seismic isolation, generally have the problems such as narrow effective damping temperature range, low damping loss factor and strong temperature dependence, which lead to prominent dependence of temperature and load conditions of the isolation performance of high-damping rubber isolation bearings. Research and development of high-performance high-damping rubber materials with broad effective damping temperature range, high damping loss factor and weak temperature dependence are very urgent and necessary to ensure the safety of the seismic isolation of engineering structures. This paper mainly reviews the recent progress in the research and development of high-damping rubber materials using nitrile butadiene rubber (NBR), epoxidized natural rubber (ENR), ethylene propylene diene rubber (EPDM), butyl rubber (IIR), chlorinated butyl rubber (CIIR), and bromine butyl rubber (BIIR). This is followed by a review of vulcanization and filler reinforcement systems for the improvement of damping and mechanical properties of high-damping rubber materials. Finally, it further reviews the constitutive models describing the hyperelasticity and viscoelasticity of rubber materials. In view of this focus, four key issues are highlighted for the development of high-performance high-damping rubber materials used for high-damping rubber isolation bearings.
... Laminated rubber bearing (LRB) is one of the simplest and most economical devices for the purpose [1,2]. Alternating layers of steel plates and rubber sheets in this device dissipates energy from ground motion before it can be transmitted to superstructure [3]. The device reduces the fundamental frequency of superstructure and thus makes it stay out of the range of ground motion frequencies that contains principal energy [4][5][6]. ...
... For the second filling condition, the void was fully filled by silica sand (H fill = 65 mm). The fill volume for ECRB and SCRB2 was approximately 282,694 mm 3 , while that for SCRB1 was approximately 150,158 mm 3 . ...
Article
Elastomeric bearing is the most common base isolation system for structures and bridges to dissipate effect of applied vibration and ground motion. To improve performance of the base isolators, lead core is implemented in the rubber bearings and it successfully enhances the damping and stiffness of elastomeric bearing. However, the most notable disadvantage of lead-core rubber bearing is the lead toxicity impact on extensive environmental contamination, which restrained application of lead in construction industry. Therefore, in the present study, an attempt has been made to develop a new elastomeric laminated bearing utilizing core-and-filler system instead of lead core to improve the performance of bearing. Two types of filler, namely granular and shape memory polymer are implemented. Granular filler is prepared by using silica sand, while shape memory polymer filler is prepared by using epoxy resin. Also, steel core is implemented to improve the stiffness of filler. The performance of proposed bearing utilizing with core-and-filler system is evaluated using finite element simulation. The numerical results revealed the efficiency of bearing with proposed system by providing considerable damping and stiffness. The replacement of lead core with fully filled granular and shape memory polymer showed improvement in terms of stiffness, and this proved core-and-filler system is effective in limiting lateral displacement. Also, the prototype of base isolation devices with both granular and shape memory polymer fillers are fabricated and tested via cyclic shear test. The results are compared with finite element analysis results, and good agreement between experimental tests results and numerical simulation response is shown. The experimental testing results proved that implementation of core-and-filler system improves the lateral resistance of proposed elastomeric bearing. In overall, it can be concluded that the implementation of core-and-filler system provides a reliable improvement to the performance of conventional elastomeric bearing and can be considered as alternative system to lead core rubber bearings.
... By the end of 2020, China had constructed more than 8000 seismic-isolated buildings. The rubber isolation system is currently the most widely used and mature isolation technology, among which the common isolation devices include the ordinary rubber bearing, natural rubber bearing (NRB) [4], LRB [5], HDRB [6], etc. The HDRB has plentiful advantages-such as a simple structure, stable mechanical performance, strong energy dissipation capacity, large stiffness before yielding, environmental protection, etc.-that make it an excellent choice for base-isolation structures. ...
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A high damping rubber bearing (HDRB) is widely utilized in base-isolation structures due to its good energy dissipation capacity and environmentally friendly properties; however, it is incapable of isolating the vertical vibration caused by earthquakes and subways effectively. Thick rubber bearings with a low shape factor have become one of the important vertical isolation forms. This paper provides an experimental comparative study on high damping rubber bearings with low shape factor (HDRB-LSF), thick lead–rubber bearings (TLRB), and lead–rubber bearings (LRB). The abilities of the bearing and energy dissipation of the above bearings are analyzed contrastively considering the influence of vertical pressure, loading frequency, shear strain, and pre-pressure. Firstly, the HDRB-LSF, TLRB, and LRB are designed according to the Chinese Code for seismic design of buildings. Secondly, cyclic vertical compression tests and horizontal shear tests, as well as their correlation tests, are conducted, respectively. The vibrational characteristics and hysteresis feature of these three bearings are critically compared. Thirdly, a corrected calculation of vertical stiffness for the thick rubber bearings is proposed based on the experimental data to provide a more accurate and realistic tool measuring the vertical mechanical properties of rubber bearings. The test results proved that the HDRB-LSF has the most advanced performance of the three bearings. For the fatigue property, the hysteresis curves of the HDRB-LSF along with TLRB are plump both horizontally and vertically, thus providing a good energy dissipation effect. Regarding vertical stiffness, results from different loading cases show that the designed HDRB-LSF possesses a better vertical isolation effect and preferable environmental protection than LRB, a larger bearing capacity, and, similarly, a more environmentally friendly property than TLRB. Hence, it can avoid the unfavorable resonance effect caused by vertical periodic coupling within the structure. All the experimental data find that the proposed corrected equation can calculate the vertical stiffness of bearings with a higher accuracy. This paper presents the results of an analytical, parametric study that aimed to further explore the low shape factor concepts of rubber bearings applied in three-dimensional isolation for building structures.
... Previous studies tried to model this complicated behaviour via nonlinear rate dependency approaches [3]. However, analytical modelling of this complex stress-strain behaviour is not a trivial task [4][5][6]. DHI model is formulated for HDRB element and recently implemented in finite element programs SAP2000 and ETABS [7], to capture different trends of behaviour within a simple constitutive model as shown in Figure 2. Detailed formulation of this model is discussed in the next section. ...
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High damping rubber bearings show highly nonlinear stress-strain behaviour. Deformation-history integral (DHI) model which can estimate small strain stiffness degradation and nonlinear plasticity via a relatively simple innovative formulation is implemented in this study to model HDRB as the rehabilitation method for a seismically vulnerable building. Considered structure in this study is a three-dimensional, four-story steel frame residential building with a concentrically braced system. Nonlinear direct integration time history analysis and plastic hinges approach were implemented to evaluate structural behaviour of considered structure. It was observed that structural responses enhanced significantly after rehabilitation. Absolute maximum base shear values decreased 61.8% and 92.2% in the worst and best cases, respectively. M ost of structural elements remained elastic after rehabilitation and required performance level was satisfied.
Article
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In this study, a seismic isolator placed on the base of a structure was optimized under various earthquake records using an adaptive harmony search algorithm (AHS). As known, the base-isolation systems with very low stiffness provide a rigid response of superstructure, so it was assumed that the structure is rigid and the base-isolated structure can be considered as a single-degree of freedom structure. By using this assumption, an optimization method that is independent of structural properties but specific to the chosen earthquake excitation set is proposed. By taking three different damping ratio limits and isolator displacement limits, the isolator period and damping ratio were optimized so that the acceleration of the structure was minimized for nine cases. In the critical seismic analysis performed with optimum isolator parameters, the results obtained for different damping ratios and isolator periods were compared. From the results, it is determined that isolators with low damping ratios require more ductility, and as the damping ratio increases, further restriction of the movement of the isolator increases the control efficiency. Thus, it is revealed that increasing the ductility of the isolator is effective in reducing the total acceleration in the structure.
Article
In the present study, a new core-and-filler system was proposed to use in elastomer bearings as a substitution to hazardous lead core while improving the performance of base isolators. The proposed system utilizes steel core and filler consists of either granular or polymer materials in relation to this proposal, both pure sand and epoxy are used as filler. Special design procedure for the proposed bearing was developed to determine the required dimension for elastomeric bearing under considered design loads according to the code of practice. The finite element model of the designed elastomeric bearing was developed to evaluate performance of the proposed bearings under design condition through nonlinear dynamic analysis. Then, parametric study was conducted to simulate various material properties and loading conditions that may occur during the manufacturing and service life of base isolation. Substantial improvement in performance of proposed bearing with core-and-filler system was observed in comparison to the lead rubber bearing. By reducing the volume of sand filler, the damping bearing of proposed sand and steel core mechanism can be improved. By manipulating the sand packing condition during manufacturing, improvement in term of effective stiffness is achievable. Trilinear constitutive curve for fully sand filled bearing revealed that, the increment in effective stiffness of bearing is higher for the shear strains more than 150%. Therefore, the core-and-filler system with full sand filler provides superior resistance against high shear strain in comparison to the lead-core rubber bearing, and achieve the purpose of limiting lateral displacement. Application of proposed elastomeric bearings in the 5-story building as base isolator has been proven the effectiveness and suitability of implementing bearing with core and fully filled sand and also with epoxy filler as alternative isolator to the lead core elastomer bearings.
Article
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.
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In this paper, a novel metal rubber bearing is proposed as an alternative to the conventional rubber bearings for small- and medium-span highway bridges to solve the aging-related issues of conventional rubber bearings such as chemical degradation and erosion. The bearing is made of porous metal wire by coiling, weaving and cold-pressing to specific shapes. A shear test program is then described on two metal rubber bearings of stainless steel wire with different densities in order to identify the characteristics of hysteretic curves. The effects of shear strain, compressive stress, loading frequency and repeated loading cycles on the hysteretic behavior were investigated. It was found that the lateral hysteretic curves are approximately in bilinear shape, which consists of an initial elastic stage and a post-yield stage. The equivalent damping ratio of the tested bearings was around 20% at 25% shear strain levels and meanwhile increased with the strain levels, indicating an appreciable energy dissipation capacity. In addition, stiffness degradation was observed for the hysteretic curves beyond a certain deformation limit due to the plastic deformation caused by wire delamination and bearing bulging. However, beyond this limit, the bearing could still work as a unit with stable hysteretic behavior. These characteristics make the metal rubber bearing a great candidate for the conventional rubber bearings. It was also found that the hysteretic behavior is related with a variety of parameters such as density, loading frequency and compressive stress. Finally, it was found that the Bouc-Wen model with appropriate input parameters representing the mechanical properties can accurately simulate the hysteretic curves of the proposed bearings.
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The paper deals with a new approach to modeling the non-conservative behavior of hard rubbers in damping structures operating under quasi-harmonic, low-frequency conditions and in the large deformation regime. In particular, a hyperelastic proportional damping (HPD) model is proposed based on experimental research of dynamic responses of cylindrical specimens to torsion excitation. The HPD model depends on two ingredients. First, it relies on the integration of the dissipated energy of an experimentally obtained steady hysteresis loop. And second, this hysteresis loop is employed to construct a so-called skeleton curve, which is utilized to obtain the parameters of a generalized Rivlin model of the hyperelastic material. In addition, attention is paid to the HPD model’s dependence on the frequency and amplitude of the torsional excitation. Finally, the problem of nonlinear transient vibration of a viscoelastic cylinder is formulated and numerically solved by the finite element method. The results obtained from finite element analyses are in accord with experimental data and validate the proposed HPD model for material damping evaluation.
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In this study, the use of high damping rubber bearing (HDRB) with various design properties in mitigating the seismic effects for steel buildings was investigated. For this, a generalized demand on the analytical model of HDRB was introduced and eighteen different models of HDRB were examined comparatively. These models were created by considering three significant isolation parameters of HDRB such as isolation period T (2, 2.5, and 3 s), effective damping ratio β (0.05, 0.10, 0.15), and post-yield stiffness ratio λ (3 and 6). The benchmark low (3-storey), mid (6-storey), and high-rise (9-storey) steel buildings were equipped with different isolation systems of HDRB and then subjected to a set of earthquake ground motions through nonlinear time history analyses in order to evaluate the actual nonlinear behaviour of the bearings in the base-isolated steel buildings in service. The base-isolated frames were assessed by the variation of the selected structural response parameters such as isolator displacement, relative displacement, inter-storey drift ratio, absolute acceleration, base shear, hysteretic curve, and dissipated energy. The effectiveness of the isolation parameters on the nonlinear response of the steel buildings with HDRB under earthquakes was comparatively evaluated to generate alternatively innovative isolation system. It was shown that the seismic performance of the base-isolated structure was remarkably influenced by the isolation parameters. The most favourable base isolation model was obtained when the higher value of the isolation period and effective damping ratio combined with the low post-yield stiffness ratio.
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This tutorial introduces the CMA Evolution Strategy (ES), where CMA stands for Covariance Matrix Adaptation. The CMA-ES is a stochastic, or randomized, method for real-parameter (continuous domain) optimization of non-linear, non-convex functions. We try to motivate and derive the algorithm from intuitive concepts and from requirements of non-linear, non-convex search in continuous domain.
Technical Report
In 2003-2004 two four-story reinforced concrete buildings belonging to IACP (SR) were seismically retrofitted by hybrid base isolation. The base isolation system for each building, consisted of 12 high-damping rubber bearings (HDRB) and 13 flat lowfriction sliding bearings (LFSB). Within the bearing supply two HDRB were kept for later testing. One of the two bearings was tested at the University of Basilicata on 11th and 12th December 2014. The present report summarizes the results of the tests.
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In the present work, we investigate the response of a hybrid base isolation system under earthquake excitation. The physical parameters of the hybrid base isolation system are identified from dynamic tests performed during a parallel project involving two residential buildings in the town of Solarino, Sicily, using the well-established optimization procedure 'covariance matrix adaptation-evolution strategy' as dynamic identification algorithm in the time domain. The base isolation system consists of high damping rubber bearings and low friction sliding bearings. Two separate models are employed for the numerical simulation of the high damping rubber bearing component, namely a bilinear system and a trilinear system, both in parallel with a linear viscous damper. In addition, a linear Coulomb friction model is used to describe the behavior of the low friction sliding bearing system. Analytical solutions are provided, in compact form, for all possible phases of motion of the hybrid base isolation system under earthquake excitation. A series of numerical simulations are carried out to highlight the behavior of the considered hybrid base isolation system under different excitation and site conditions.
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multilayer rubber bearings as vibration isolation bearings;multilayer rubber bearings in mechanical and automotive engineering;equipment isolation from vibration via anti-vibration;vibration isolation in concert halls, Benaroya Concert Hall in Seattle;seismic isolation and multilayer rubber bearings;Los Angeles City Hall, a 28-story steel frame building;bearings for Hearst Memorial Mining Building, University of California;base-isolated four-story reinforced concrete building and UNIDO-sponsored program
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A fractional derivative Zener (FDZ) model connected in parallel with a linear viscous damper and a Coulomb friction slider is used to numerically simulate the mechanical behavior of a base isolated (BI) building tested under free vibration conditions in Solarino, Sicily. This hybrid BI system comprises high damping rubber bearings in combination with low friction sliding bearings. A comparison study of the present model with previous ones appearing in the literature, namely the bi-linear and the tri-linear models defined in the time domain, is carried out here. Furthermore, the linear viscoelastic solid, namely the classical Zener model, is also implemented and evaluated. The rheological models representing all the above BI systems are analyzed and, for the first time, the rheological formulation for the tri-linear model is presented. The present comparison study shows that the FDZ model is capable of describing the complex nonlinear response of BI systems.
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Design Example for a High-Damping Rubber Bearing Design Example for a Lead-Plug Bearing
An Introduction to Rubber Technology. Southampton: Rapra Technology Limited
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Ciesielski A. An Introduction to Rubber Technology. Southampton: Rapra Technology Limited; 1999.