High Damping Rubber Research Articles

Tunable Van der Waals interfacial interaction for ultrahigh-damping rubber bends

High-damping rubber materials are of crucial significance for realizing high-performance green tire due to their contributions in noise and vibration reduction, auto-braking, and service life. However, the polarity difference and mismatched surface energy significantly reduce the interfacial interaction and compatibility between non-polar tread rubber materials and polar polymers. Herein, we fabricated a multi-functionalization high vinyl polybutadiene rubber (MFHVBR)/ethylene-vinyl acetate rubber (EVM) blend by simple mechanical blending. The incorporation of polar functional groups could increase the surface energy of MFHVBR, which was beneficial for regulating the interfacial compatibility and van der Waals interaction between non-polar rubber matrix and polar polymer matrix. A quantitative correspondence between van der Waals interaction and damping properties was determined. The optimized MFHVBR/EVM blends showed ultrahigh damping properties with an effective damping temperature range of −12.4–62.6 °C, which totally covered the service temperature of tires. The effective damping temperature range width of 75 °C was among the highest value of reported high-damping rubber materials. Meanwhile, the vulcanization efficiencies and physical mechanical properties were obviously improved. Collectively, the developed strategy herein and the proposed surface energy-performance relationship suggest a feasible pathway toward low-cost and high-performance green tire tread rubber materials.

Seismic collapse probability and life cycle cost assessment of isolated structures subjected to pounding with smart hybrid isolation system using a modified fuzzy based controller

The possibility of pounding on isolated structures with surrounding moat walls is one of the concerns in the design of isolation systems, especially in pulse-type near-field earthquakes. This paper puts forward the seismic probability assessment of structures equipped with passive and smart hybrid isolation systems by considering pounding possibilities. This investigation is performed on isolated structures equipped with a high damping rubber bearing (HDRB) considering stiff moat walls around the structure. In the Hybrid isolation system, magnetorheological dampers (MR) are considered an adaptive dissipation energy device along with isolators using an optimized novel interval Type-2 fuzzy logic controller with adaptive red-zone function (IT2FS + RZF) to reduce pounding possibilities. The fragility curves of the building for various cases are determined using incremental dynamic analysis (IDA), and possible damage costs are evaluated by using exceedance probability in each damage level. This study concludes that the collapse probability of the isolated structures with restrains at the code-based distance is over the acceptable limit of ASCE 7–22. The smart additional damping system with the proposed controller reduces the possible damage cost of the building by about 64 % compared to the uncontrolled system and puts the collapse probability of the structure in the acceptable range.

Research and Development of High-Performance High-Damping Rubber Materials for High-Damping Rubber Isolation Bearings: A Review.

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.

Near-fault earthquakes with pulse-like horizontal and vertical seismic ground motion components: Analysis and effects on elastomeric bearings

Near-fault earthquakes have been largely studied in the last years by paying special attention to the occurrence of a pulse-like horizontal seismic ground motion, and to the related effects on structural systems. Conversely, less attention has been paid on the vertical component of the ground motion in such seismic events. Within this framework, the present study is meant at investigating a fairly overlooked special case, that is the occurrence of near-fault earthquakes exhibiting a pulse-like seismic ground motion along the horizontal direction and the vertical one. Specifically, the variational mode decomposition technique is employed to prepare and characterize two subsets of near-fault earthquake records that consist of fault-normal and vertical seismic ground motion components. One subset collects earthquake records with pulse-like waveform in both velocity components, whereas a pulse-like waveform in the fault-normal velocity component only takes place in the earthquake records of the second subset. If both fault-normal and vertical components embed a dominant pulse-like waveform, then it is found that the ratio of the corresponding pulse periods well correlates with the pulse period along the fault-normal direction, while it is uncorrelated with respect to the pulse period along the vertical direction. Next, it is investigated the displacement demand of high-damping rubber bearings for base-isolated buildings under earthquake records characterized by a horizontal impulsive ground motion together with either a pulse-like or a nonpulse-like vertical shaking, provided that the pulse period in the horizontal direction is similar and the peak ground accelerations are individually the same after scaling. Final results shows that the maximum displacement of elastomeric bearings subjected to a pulse-like horizontal ground motion is moderately amplified, on average, when the vertical excitation is also pulse-like.

Physical Properties of Slide-Ring Material Reinforced Ethylene Propylene Diene Rubber Composites

High-damping rubber composites were prepared by mixing ethylene propylene diene monomer rubber (EPDM) with slide-ring (SR) materials using a two-roll mill, followed by a compression molding technique. SR material has a novel supramolecular structure with unique softness and slidable crosslink junctions. The mechanical strength, thermal stability, compression set property, and damping performance of the composites were investigated. The use of the high damping SR phase dispersed in the EPDM matrix displayed improved physical properties and damping performance compared to those of virgin rubber. As SR content increases in the composites, the damping factor of SR/EPDM blends becomes higher at room temperature. In addition to this, the SR composites showed excellent improvements in the compression set properties. The composites showed a compression set improvement of 35–38% compared to virgin EPDM. These improvements are due to the “pulley effect” of slide-ring materials. Therefore, these materials present a robust platform for making novel elastomer composites for high-performance damping and sealing applications.

Seismic damage analysis of Yematan Bridge under near-fault earthquakes

On May 22, 2021, a magnitude 7.4 (Ms) earthquake, the largest earthquake in mainland China since the Wenchuan magnitude 8.0 (Ms) earthquake, occurred in Maduo County, Qinghai Province, China. The Maduo earthquake caused significant damage to the Yematan Bridge near the fault and epicenter, which resulted in excessive girders movement and the widespread failure of high damping bearings. The seismic performance of the Yematan Bridge was studied by finite, which simulated the mechanical behavior of the shear key and high damping bearings. To better restore the seismic damage situation, nonlinear analysis is carried out by using two constitutive models of high damping rubber bearings with and without damage. The ground motion input contains near-fault features concluded directivity effect and fling step, and genetic algorithm is used to find the optimal ground motion amplitude for seismic response analysis. The analysis showed that one of the essential reasons for the severe damage to the bridge is that the bridge axis is close to the predominant seismic angle, and the bearing was damaged by the directivity effect. The calculation results obtained by considering the bearing failure constitutive model are closer to the field investigation of earthquake damage. Finally, corresponding seismic measures and suggestions are proposed according to the seismic damage situation and mechanism of the bridge.

Influence of ground motion duration on seismic performance of RC frame isolated by high damping rubber bearings

The high damping rubber bearing (HDRB) is an advanced seismic isolation component currently used in building structures with sound energy dissipation capacity. This study examines the effects of ground motion duration on the seismic performance of reinforced concrete frame isolated by HDRBs. The effect of ground motion duration is isolated from other effects due to ground motion amplitude and acceleration spectral shape by using 44 pairs of short-duration and long-duration spectrally equivalent ground motions. Nonlinear time-history analyses are conducted on a base-isolated building using HDRBs. The numerical analyses considered the calibrated parameters of the HDRB model based on experimental data. The stiffness degradation of the HDRBs due to Mullins’ effect under cyclic loading is accounted into the numerical model. The influence of ground motion duration is evaluated by comparing the seismic responses of the isolator components and the superstructure. The results indicate that the ground motion duration generates a significant influence on seismic responses. The influence varies as the ground motion intensity changes. The stiffness degradation of the HDRB becomes evident with the increase of the earthquake intensity, and the effect of such degradation on the structural responses is more significant when under long-duration ground motions.

Influence of freeze–thaw cycles and aging on the horizontal mechanical properties of high damping rubber bearings

Influence of freeze–thaw cycles and aging on the horizontal mechanical properties of high damping rubber bearings

Influence of Internal Rubber Damper on Cable External Viscous Damper Effectiveness

In practice, the internal rubber dampers are widely installed inside the cable guide pipe between the external viscous damper and the cable anchorage. In order to study the effect of the internal damper on the performance of the external viscous damper, the theoretical analysis model of a taut cable with an internal rubber damper and an external viscous damper is established in this paper, where the internal damper is assumed to be a high damping rubber damper with a flexible support and the external damper is considered to be a linear viscous damper. Then, the numerical iterative formula and approximate solution expression for the cable modal damping ratio are derived. Based on the approximate solution, the parameters of the internal rubber damper are analyzed comprehensively, and its influence on the cable modal damping in cable multimode is studied as well. Results show that, except for the support flexibility of the internal rubber damper, other parameters will have a negative effect on external viscous damper effectiveness. From the perspective of cable multimode vibration control, the installation of an internal rubber damper significantly weakens the modal damping, and this effect is more pronounced in lower frequency modes.

Seismic reliability of base isolated systems: sensitivity to design choices

Seismic isolation is considered an effective solution to protect buildings and related content from earthquakes, and consequently reduce seismic losses. However, the overall reliability levels achieved on these systems by following the design rules suggested by codes are not uniform and they may be strongly influenced by some choices made in the structural design. This study aims to investigate the seismic reliability of structural systems equipped with high-damping rubber bearings, which is a widely used class of isolators. An extensive parametric analysis is performed to assess the influence of design choices on the failure probability, considering design parameters concerning both the isolation system and the superstructure, such as: isolation period; bearings shear strain; percentage of flat sliders (i.e., bearing shape factors); superstructure overstrength ratio. A set of case studies have been configurated by varying and combining all the aforesaid parameters. A stochastic model is used for the bidirectional seismic input and the generation of horizontal ground motion components, whereas full probabilistic analyses are performed via Subset Simulation to achieve accurate estimates of the demand hazard curves up to very small failure probabilities. To reduce the computational effort, a 3D-model with a reduced number of DOFs (Degrees of Freedoms) is adopted for each case study. It consists of an uncoupled bidirectional elastoplastic model of the superstructure, and an advanced nonlinear 3D model of the rubber isolators, accounting for the coupling between vertical and horizontal response in large displacements. For each case analysed, demand hazard curves are evaluated to illustrate the probabilistic properties of the seismic response for both isolation system and superstructure. Results show a noticeable sensitivity of the system reliability with respect to the examined design choices and in some cases the achieved structural performance can be far from the safety levels required by the Codes.

Isolation design and numerical calculation of isolated rubber bearing in continuous beam bridge in high seismic intensity area

The stability of bridges in the face of earthquake hazards has always been the focus of construction engineering. At present, a large number of bridge construction has begun to use isolation rubber bearings to increase the seismic capacity of bridges. However, in the face of high-intensity earthquake disasters, the seismic performance of the bridge is gradually unable to meet, the main reason is the lack of relevant research on the seismic performance of the bridge in high seismic intensity area. Therefore, this study will explore the changes of the bridge in the face of high-strength earthquake, and try to use high damping rubber bearings for the isolation design of the bridge. By establishing the finite element model of continuous bridge combined with isolation rubber bearing, the numerical calculation of bridge element is carried out on this basis, and the isolation effect of isolation rubber bearing is analyzed. The results show that the compression resistance and shear resistance of the isolated rubber bearing are strong. Under the influence of different seismic waves, the maximum displacement of the bearing is 0.131 m and the maximum horizontal force is 389.6 kN, which are lower than the allowable value of the bridge, and the overall seismic performance of the bridge has been significantly improved, which can play a good theoretical support in the construction of continuous bridges in high seismic intensity areas.

Preparation and characterization of natural rubber–based new elastomers for high-damping base isolation systems

Natural rubber (NR)–based vulcanizates have been used as base isolation materials for many years. Combining good damping properties, low cost, and availability with acceptable mechanical and aging performance, these materials have always been the first choice for base isolation applications. In this research, we try to formulate a natural rubber base recipe with increased damping properties, which can fulfill mechanical and aging requirements of base isolation systems. For this purpose, a series of blends have been formulated by incorporating chloroprene (CR) or butadiene (BR) and acrylonitrile butadiene rubber (NBR) into the natural rubber base. Filler content accelerator type and vulcanization system have been chosen to optimize damping while maintaining a reference point. All vulcanizates have been tested for their mechanical properties. Moving die rheometer (MDR) and rubber process analyzer (RPA) have been used to obtain general cure data as well as storage (G′) and loss modulus and loss angle (η). Crosslink densities have been calculated using RPA and Lee and Pawlowsky’s Coran approach. Dynamic material tests have been performed to obtain dynamic shear properties, equivalent damping ratio, and shear modulus. The results indicated that NR/NBR and NR/CR compounds with viscous damping values of 10.4% and 8.9% at frequency of .5 Hz can lay bases for formulating high-damping rubber (HDR) materials for base isolation systems due to their increased damping and rather good mechanical and relaxation performance.

Development of floating rubber-concrete isolation slab system for 3D vibrations

Nowadays by implementing of various machineries and equipment, the structures are subjected to multidirectional vibrations as combination of vertical and horizontal cyclic oscillations. The slabs are the main structural components, imposed to the dynamic loads due to vibrating generator machines and the load is transferring from slabs to the foundation through the girders and columns.Recently, application of the high damping rubber bearings to the structures as base isolator systems to dissipate imposed dynamic loads is frequently considered by design engineers, mainly for controlling horizontal vibrations. However, in order to isolate machine-induced vibrations, it is required to isolate the machine itself within the story.Therefore, in the present research an attempt has been made to develop a floating rubber-concrete isolation slab system (FRCISS) by implementing High Damping Rubber (HDR) under the floating slab system. The components of the proposed system are designed based on required criteria and the performance of the developed FRCISS in reducing vibrations in both horizontal and vertical directions are investigated through finite element method.Thereafter, two prototypes of FRCISS slabs have been casted and experimentally tested under horizontal and vertical cyclic loadings by using dynamic actuator in order to validate the model. Eventually, the new proposed FRCISS is applied on lab-size 3-story, 1-bay buildings numerically. In each building, the floating system is installed within a different story and is subjected to dynamic load. Then the dynamic response of the structures with floating systems are compared with the dynamic response of conventional structures in order to assess the capability of FRCISS to diminish vibration effect.For interior vibrations, the lateral drifts in the structure with floating systems in the 1st, 2nd, and 3rd stories under horizontal cyclic loading were reduced by an average 87.33%, 62.21% and 47.08%, compared to lateral drifts in conventional structures, respectively, while the deflection under vertical loading was reduced by 11.1%. Whereas, the average drift reduction values were 69.68%, 26.08%, and 20.18% under the north-south seismic component, and 74.03%, 17.1%, and 16.55% under the east-west seismic component, for the modified buildings compared to conventional buildings. The current study contribution is summed up in demonstrating the possibility of implementing HDR in the floating slabs to isolate horizontal and vertical vibrations and protect the machinery.

Observed Seismic Behavior of a HDRB and SD Isolation System under Far Fault Earthquakes

The behavior of a reinforced concrete building, seismically isolated with high damping rubber bearing (HDRB) and sliding devices (SD), observed during the most important events of the seismic sequence that struck central Italy from August 2016 to January 2017, is analyzed. Due to the epicenter distances, all the events had light effects at the site, thus the isolation system was not always put into action. A previous very low energy earthquake and the ambient vibration analysis are used for comparison. The study of the isolation system response is first carried out and the variability of the resonance frequencies with the input energy at the site is pointed out. These frequencies are quite close to those of the superstructure considered as fixed base. Small cracks were observed after the sequence in some partition walls of the building. The analysis of the superstructure was performed by means of a finite element model, assuming a non-linear model for the isolators, based on previous experimental data. The importance of a suitable decoupling between the superstructure and the ground and the contribution of the sliding devices under low energy earthquake is pointed out.

Experimental and analytical studies on mechanical performance of innovative energy-dissipating hold-down for CLT structures

Connection is the most important part in cross-laminated timber (CLT) buildings as it guarantees necessary strength, stiffness, ductility, and integrality for the whole CLT structure. This paper proposes an innovative energy-dissipating hold-down connection for CLT structures, which combines the advantages of the soft-steel bracket and high-damping rubber for providing great energy-dissipating capacity and high ductility. A series of tests were performed under quasi-static monotonic and reversed cyclic loading to investigate the failure mechanisms and mechanical properties of the novel hold-down connection. Test results demonstrate that the connections can continue to work as a whole even after the occurrence of preliminary failures of steel ribs rupture and weld fracture. Final failure modes, including debonding between the rubber and steel plates, rupture of the front steel plate and breakage of screws, caused the invalidation of the connection. Meanwhile, load–displacement curves of the connections usually exhibit a bi-linear form, and the connection’s yielding is caused by the yielding of steel ribs. All the tested specimens exhibited stable energy-dissipating capacity in the working stage and were all classified as highly ductile. Furthermore, efforts were made to develop a simplified analytical model for estimating the basic mechanical properties of the novel hold-down connections. Comparison with test results shows that the analytical model can provide reasonable estimations of the initial stiffness, post-yield stiffness, yield force and failure force. The test results and analyses presented herein provide useful technical bases for supporting future studies and practical applications of the novel hold-down connection for CLT buildings.

Theoretical Investigation on the Impact of Two HDR Dampers on First Modal Damping Ratio of Stay Cable

Stay cables are one of the vital components of a cable-stayed bridge. Due to their flexible nature, stay cables are vulnerable to external excitation and often vibrate with large amplitude under wind action which leads to the fatigue failure of the cables. To suppress such kind of large amplitude vibration by improving the damping ratio of the cable various dampers such as magnetorheological damper, friction damper; oil damper; or high damping rubber (HDR) damper are utilized and gained popularity over time. This paper focuses on improving the damping ratio of stay cables using a combination of two HDR dampers. First, the theoretical model is formulated considering cable bending stiffness to evaluate the damping effect of cable-HDR dampers system. Then, the impact of various design parameters of HDR dampers on cable damping considering the cable stiffness is performed. The comparative analysis of results shows that the considered parameters such as loss factor, spring factor, and installation location of dampers have much effect on the stay cables damping ratio. Finally, the optimal parameters of the two HDR dampers are proposed for damper design.

Analysis method of isolation layer composed of high damping rubber bearings based on deformation history integral type model

As the high damping rubber bearings (HDRBs) presents stronger nonlinear material effects, the deformation history integral type model (DHI model) validated to well simulate the mechanical behaviors was adopted instead of traditional bilinear model. While considering the computational cost of the nonlinear time history (NLTH) analyses, simplified analysis methods represented by the equivalent linearization (EL) method has been widely applied to estimate the structural response, especially in the cases where isolated structures can be simplified to single-degree-of-freedom systems. The EL parameter calculation formulas based on the DHI model was derived to realize the equivalent linearization analysis of isolation layer composed of HDRBs, and the formulas were applied to an iterative process for calculating the maximum deformation of the isolation layer. A six-story isolated building was taken as an example to verify the accuracy of the proposed method. It was shown that the estimated results of the iterative approach have limited difference with the structure responses obtained from NLTH analyses. Therefore, the established model can be further applied for the assessment of the seismic demands of structures isolated by HDRBs.

A Nonlinear Model and Parameter Identification Method for Rubber Isolators under Shock Excitation in Underwater Vehicles

Rubber isolators are usually used to protect high-precision equipment of autonomous underwater vehicles (AUVs), avoiding damage from overlarge dynamic excitation. Considering the nonlinear properties of the rubber material, the nonlinear behavior of rubber isolators under shock exaltation is hard to be predict accurately without the available modal and accurate parameters. In view of this, the present study proposes a nonlinear model and parameter identification method of rubber isolators to present their transient responses under shock excitation. First, a nonlinear model of rubber isolators is introduced for simulating their amplitude and frequency-dependent deformation under shock excitation. A corresponding dynamic equation of the isolation system is proposed and analytically solved by the Newmark method and the Newton-arithmetic mean method. Secondly, a multilayer feed-forward neural network (MFFNN) is constructed with the current model to search the parameters, in which the differences between the estimated and tested responses are minimized. The sine-sweep and drop test are planned with MFFNN to build the parameter identification process of rubber isolators. Then, a T-shaped isolator composed of high-damping silicon rubber is selected as a sample, and its parameters were determined by the current identification process. The transient responses of the isolation system are reconstructed by the current mode with the identified parameter, which show good agreement with measured responses. The accuracy of the proposed model and parameter identification method is proved. Finally, the errors between the reconstructed responses and tested responses are analyzed, and the main mode of energy attenuation in the rubber isolator is discussed in order to provide an inside view of the current model.

An Experimental Study on the Mechanical Properties of a High Damping Rubber Bearing with Low Shape Factor

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.

Seismic performance of bridges with novel SMA cable‐restrained high damping rubber bearings against near‐fault ground motions

AbstractThis study presents a novel type of shape memory alloy (SMA) cable‐restrained high damping rubber (SMA‐HDR) bearing, which is particularly suited to near‐fault (NF) regions where the pulsing effect potentially exists in the ground motions. The working mechanism of the bearing is first described, followed by an experimental investigation on a full‐scale SMA‐HDR bearing specimen. The test results confirm the efficient restraining effect offered by the SMA cables, which contribute to 65% and 24.4% of the lateral load resistance and total energy dissipation, respectively, prior to the initial fracture of the SMA cables. The failure of the cables is initiated near the end grip where moderate stress concentration exists at this region. Following the experimental study, the numerical modeling strategy for the bearing is discussed, and a case study is then presented, demonstrating the application of the SMA‐HDR bearings in the Datianba #2 highway bridge, a real project that first adopts the proposed bearings in the world. A simplified design process is introduced for the bridge with novel SMA‐HDR bearings to mitigate the potential damage during strong earthquakes especially the NF ones. The system‐level analysis on the prototype bridge shows that the novel SMA‐HDR bearings equipped with ten 7×7×1.2 SMA cables in each bearing could reduce the average maximum bearing displacement (MBD) by nearly 30% compared with the conventional bridge with HDR bearings. The application of the novel SMA‐HDR bearing can significantly alleviate the pounding effect, especially under the NF earthquakes. The presence of the SMA cables tends to increase the maximum force response of the piers, but this effect is minor and under control.