scholarly journals The Experimental Study on Mechanical Behavior of Conveyor Belt Rubber Bearings

2020 ◽  
Vol 10 (13) ◽  
pp. 4452
Author(s):  
Yifeng Wu ◽  
Yan Zhang ◽  
Aiqun Li ◽  
Guodong Zhang
Keyword(s):  
Shear Strain ◽  
Seismic Isolation ◽  
Low Cost ◽  
Damping Ratio ◽  
Influencing Factor ◽  
Core Layer ◽  
Conveyor Belt ◽  
Vertical Stiffness ◽  
Property Losses ◽  
Rubber Bearings

Fabric core conveyor belt rubber bearing (CBRB) with low cost and a simple manufacturing process has been proposed to further popularize seismic isolation technology in low-rise buildings, and four samples of such bearings have been produced, including four-layer, five-layer, five-layer with inner pattern and six-layer fabric core CBRBs. The vertical compression and the compression shear test are carried out to evaluate the performances of the four bearings. Results show that the vertical stiffness of the CBRB increases as the number of fabric core layer increases, while the damping ratio decreases, and the bearings can withstand a vertical pressure of 10 MPa. In addition, these bearings work very well within 100% shear strain, and the horizontal stiffness of the bearings decreases with increasing shear strain. In the meantime, as the number of fabric core layer increases, the effective horizontal stiffness of the bearings increases under 4 MPa compressive stress, and the damping ratio coefficient of the bearing is about 15%, when bearing sliding does not occur. The ultimate shear strain reached up to 200% for the four-layer bearing with obvious interlayer cracks, which means that the bonding quality between layers is the key influencing factor on the ultimate shear strain. In short, the proposed low-cost bearing has low horizontal stiffness and good energy dissipation capacity, so it is suitable for low-rise buildings in economically underdeveloped, high intensity areas, which can significantly improve their earthquake resistance and reduce casualties and property losses.

scholarly journals Analytical and Experimental Overview of Fiber Reinforced Elastomeric Isolator

2021 ◽  
Vol 9 (VII) ◽  
pp. 3906-3911
Author(s):  
Afroz Qureshi
Keyword(s):  
Seismic Isolation ◽  
Seismic Waves ◽  
Base Isolation ◽  
Low Cost ◽  
Fiber Reinforced ◽  
Effective Response ◽  
Isolation System ◽  
Vertical Stiffness ◽  
Base Isolation System ◽  
Fiber Reinforced Elastomeric Isolator

There has been many researches in order to further improve the Base Isolation system by trying various combinations and alternative materials. In that fiber reinforced isometric isolators are emerged as a viable solution, because for the low cost and effective response to seismic waves as compared to the conventional isolators. Studies further shows that it provides high vertical stiffness and low horizontal stiffness, also having effective damping over the conventional one. Developing countries who doesn’t have proper seismic protection solutions have found this convenient as they are comparatively less in cost and doesn’t require complex installation. Studies also shows Un-bonded FREI has lower horizontal stiffness and considerably lower stress demand on rubber material as compared to the B-FREI and hence significantly higher seismic isolation efficiency.

Implementation and Validation of a Numerical Model for Lead-Rubber Seismic Isolation Bearings

2017 ◽  
Vol 35 (02) ◽  
pp. 153-165 ◽  
Author(s):  
T. Zhou ◽  
Y. F. Wu ◽  
A. Q. Li
Keyword(s):  
Numerical Model ◽  
Seismic Isolation ◽  
Model Simulation ◽  
Lateral Displacement ◽  
Piecewise Linear ◽  
Stability Limit ◽  
Lateral Interaction ◽  
Vertical Stiffness ◽  
Lead Rubber Bearings ◽  
Rubber Bearings

ABSTRACTThis paper presents a numerical model for accurately representing the behaviors of lead-rubber bearings during earthquakes. This model, which is implemented in OpenSees as a user-defined element, accounts for the mechanical characteristics of bearings as follows: firstly, the bi-lateral interaction effect of hysteretic behaviors, as well as the variation in horizontal stiffness due to vertical load, is considered; secondly, the reduced vertical stiffness under large lateral displacement is incorporated by the piecewise linear formulation, and the linear reduction method is employed to determine the stability limit of bearings in the deformed configuration; furthermore, the cavitation and permanent damage effects in bearings are mathematically included. To validate the numerical model, simulation analyses are performed for a series of static and dynamic loading tests, and the numerical results show reasonable agreement with experimental ones, which indicates that the proposed model provides an effective tool for the failure mode analyses of bearings and the dynamic analyses of seismic isolated structures.

Hysteretic Restoring Force Characteristics of High Damping Rubber Bearings Under High Compressive Stress

2004 ◽  
Author(s):  
Yasuhiro Kasahara ◽  
Shigenobu Suzuki ◽  
Takashi Kikuchi
Keyword(s):  
Compressive Stress ◽  
Seismic Isolation ◽  
Damping Ratio ◽  
Loading Test ◽  
Restoring Force ◽  
Scaled Model ◽  
High Damping Rubber Bearings ◽  
High Damping Rubber ◽  
Rubber Bearings ◽  
Force Characteristics

Hysteretic restoring force characteristics — shear stiffness, equivalent damping ratio, and ultimate properties — of seismic isolation bearings are significantly affected by compressive stress. In this study, dependence of shear properties of high-damping rubber bearings (HDR) on the compressive stress σ and secondary shape factor S2 was studied by dynamic loading test with scaled-model and static loading test with full-scale isolators. The results highlighted the high compressive stress dependency on restoring force characteristics of HDR with the isolator of relatively small S2. It is concluded that large S2 is desired when isolators are designed for high compressive stress. The applicability of HDR under high compressive stress was experimentally verified.

Seismic Isolation Design for Approach Spans of Suiwei Bridge in Wenchuan

2011 ◽  
Vol 71-78 ◽  
pp. 1444-1450
Author(s):  
Wen Zheng Zhu ◽  
Zhong Gen Xu
Keyword(s):  
Energy Dissipation ◽  
Seismic Isolation ◽  
Design Method ◽  
Response Spectrum ◽  
Damping Ratio ◽  
Time History ◽  
Large Earthquake ◽  
Bridge Design ◽  
Dynamic Time ◽  
Rubber Bearings

The process and thought for the approach bridge of Suiwei bridge design using the method of isolation and energy dissipation were proposed in this paper. The concept of protecting a bridge from the damaging effects of an earthquake by introducing isolating bearings to isolate it from the moving ground is an attractive one. Firstly, the sizes of the laminated rubber bearings and the dia- meters of lead plugs are calculated with static analysis. Then the internal forces of the piers and the damping ratio of the isolated bridge needed to restrict the seismic deformation to 8cm during earth- quakes with seldom intensity were calculated using the Response Spectrum Method, and the result verified with dynamic time history method demonstrates that the Response Spectrum Design Method can restrict the girder displacement to 8cm during large earthquake and reach the goal of 25 percent shock reduction. The design process can be of reference to the bridge design with isolation and energy dissipation.

EFFECTIVENESS OF SEISMIC ISOLATION FOR CABLE-STAYED BRIDGES

2006 ◽  
Vol 06 (01) ◽  
pp. 77-96 ◽  
Author(s):  
B. B. SONEJI ◽  
R. S. JANGID
Keyword(s):  
Seismic Response ◽  
Seismic Isolation ◽  
Damping Ratio ◽  
Time History ◽  
Time Interval ◽  
Lumped Mass ◽  
Pendulum System ◽  
Isolation Systems ◽  
Rubber Bearings ◽  
Cable Stayed Bridges

This paper investigates the effectiveness of elastomeric and sliding types of isolation systems for the seismic response control of cable-stayed bridges. A simplified two-dimensional lumped-mass finite-element model of the Quincy Bay-view Bridge at Illinois was developed for the investigation. The seismic isolation of cable-stayed bridges is achieved using three different isolators, namely, high damping rubber bearings (HDRB), lead rubber bearings (LRB) and friction pendulum system (FPS). Time history analysis is performed for the bridge with four different earthquake ground motions applied in the longitudinal direction using Newmark's method with linear variation of acceleration over the time interval. The seismic response of the isolated cable-stayed bridge is compared with that of the bridge with no isolation system. The results show that the isolation systems are effective for reducing the absolute acceleration of the deck and the base shear response of the tower. Further, a parametric study is performed by varying the damping ratio, yield strength and friction coefficient of HDRB, LRB and FPS to investigate the influence of these parameters on the seismic response of the bridge. From such a study, optimal values can be found for the isolators for reducing the bridge responses.

scholarly journals Horizontal-Vertical-Rocking Coupled Response Analysis of Vertical Seismic Isolated Structure under Near-Fault Earthquakes

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Dewen Liu ◽  
Yafei Zhang ◽  
Sitong Fang ◽  
Yang Liu
Keyword(s):  
Seismic Isolation ◽  
Damping Ratio ◽  
Vertical Displacement ◽  
Response Analysis ◽  
Isolation System ◽  
Vertical Stiffness ◽  
Near Fault ◽  
Isolated Structures ◽  
Nonlinear Dynamic Analyses ◽  
Near Fault Earthquakes

For vertical isolated structures with excessive vertical eccentricity for mass and vertical stiffness, horizontal-vertical-rocking response needs to be better understood for vertical isolated structures located in near-fault areas, where long-period velocity pulse can be produced. In this study, a seismic isolation system including quasizero stiffness (QZS) and vertical damper (VD) is used to control near-fault (NF) vertical earthquakes. The responses of horizontal-vertical-rocking coupling base-isolated structure including quasizero stiffness (QZS) and vertical damper (VD) subjected to NF horizontal and vertical ground motions are investigated. Nonlinear dynamic analyses are conducted to study the effects of essential parameters such as isolation system eccentricity, static equilibrium position, vertical isolation period, and vertical damping ratio on seismic responses of vertical isolated structure. It is found that increasing vertical period and damping ratio causes the vertical isolated structures to behave well in reducing rocking responses of structure. The effect of horizontal-vertical-rocking coupling on vertical seismic isolation efficiency is insignificant. The vertical seismic isolation remains effective as compared to the system supported on rubber bearings. The vertical damping can significantly control the vertical displacement and rocking moment.

Rotordynamic Performance of Flexure Pivot Hydrostatic Gas Bearings for Oil-Free Turbomachinery

2007 ◽  
Vol 129 (4) ◽  
pp. 1020-1027 ◽  
Author(s):  
Xuehua Zhu ◽  
Luis San Andrés
Keyword(s):  
High Speed ◽  
Low Cost ◽  
Damping Ratio ◽  
Extreme Temperature ◽  
Gas Bearings ◽  
Speed Increase ◽  
Feed Pressure ◽  
Motor Test ◽  
Direct Stiffness ◽  
Commercial Applications

Micro-turbomachinery demands gas bearings to ensure compactness, light weight, and extreme temperature operation. Gas bearings with large stiffness and damping, and preferably of low cost, will enable successful commercial applications. Presently, tests conducted on a small rotor supported on flexure pivot hydrostatic pad gas bearings (FPTPBs) demonstrate stable rotordynamic responses up to 100,000rpm (limit of the drive motor). Test rotor responses show the feed pressure raises the system critical speed (increase in bearing direct stiffness) while the viscous damping ratio decreases. Predictions correlate favorably with experimentally identified (synchronous) direct stiffness bearing force coefficients. Identified experimental gas bearing synchronous damping coefficients are 50% or less of the predicted magnitudes, though remaining relatively constant as the rotor speed increases. Tests without feed pressure show the rotor becomes unstable at ∼81krpm with a whirl frequency ratio of 20%. FPTPBs are mechanically complex and more expensive than cylindrical plain bearings. However, their enhanced stability characteristics and predictable rotordynamic performance makes them desirable for the envisioned oil-free applications in high speed micro-turbomachinery.

Shear Modulus and Damping Ratio of Gravel Material

2011 ◽  
Vol 105-107 ◽  
pp. 1426-1432 ◽  
Author(s):  
De Gao Zou ◽  
Tao Gong ◽  
Jing Mao Liu ◽  
Xian Jing Kong
Keyword(s):  
Shear Modulus ◽  
Shear Strain ◽  
Strain Amplitude ◽  
Damping Ratio ◽  
Confining Pressure ◽  
Dynamic Shear Modulus ◽  
Test Results ◽  
Dynamic Shear ◽  
Data Points ◽  
Shear Strain Amplitude

Two of the most important parameters in dynamic analysis involving soils are the dynamic shear modulus and the damping ratio. In this study, a series of tests were performed on gravels. For comparison, some other tests carried out by other researchers were also collected. The test results show that normalized shear modulus and damping ratio vary with the shear strain amplitude, (1) normalized shear modulus decreases with the increase of dynamic shear strain amplitude, and as the confining pressure increases, the test data points move from the low end toward the high end; (2) damping ratio increases with the increase of shear strain amplitude, damping ratio is dependent on confining pressure where an increase in confining pressure decreased damping ratio. According to the test results, a reference formula is proposed to evaluate the maximum dynamic shear modulus, the best-fit curve and standard deviation bounds for the range of data points are also proposed.

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