Restoring Force Characteristics of Laminated Rubber Bearings Under Various Restraining Conditions

2004 ◽  
Vol 126 (1) ◽  
pp. 141-147
Author(s):  
Nobuo Masaki ◽  
Shigenobu Suzuki
Keyword(s):  
Bending Moment ◽  
Combined Loading ◽  
Loading Test ◽  
Restoring Force ◽  
Shape Factors ◽  
Rubber Bearing ◽  
Laminated Rubber Bearing ◽  
Degree Of Restraint ◽  
Rubber Bearings ◽  
Force Characteristics

We conducted the measurement of restoring force characteristics of laminated rubber bearings under various restraining conditions. In the experiment, we provided three laminated rubber bearings with various second shape factors S2=3,4,4.94. The restoring force is obtained by using a newly designed combined loading test apparatus. By using this apparatus, the laminated rubber bearing could be subjected to shear, compressive and rotational deformations independently. In this experiment, we defined the degree of restraint as the ratio of the bending moment to the restricting bending moment which was measured when the rotation angle of the laminated rubber bearing was zero radian. This means that the flanges on both sides of the laminated rubber bearings were kept parallel during horizontal deformations. From the experiment, it was confirmed that restoring force characteristics were affected by the degree of restraint. Some reduction in restoring forces was observed when the degree of restraint was small. In particular the laminated rubber bearing with a small second shape factor, namely the rubber bearing, had a slender shape, easily buckling under small horizontal displacement. It was also confirmed that bending stiffness of the laminated rubber bearing had shear strain dependency and vertical load i.e., surface pressure dependency. The results of this experiment reveal that we should consider the reduction of the restoring force if the upper or lower structure of the laminated rubber bearing is not sufficiently rigid.

Development on Rubber Bearings for Sodium-Cooled Fast Reactor: Part 3 — Ultimate Properties of a Half Scale Thick Rubber Bearings Based on Breaking Test

2016 ◽  
Author(s):  
Tsuyoshi Fukasawa ◽  
Shigeki Okamura ◽  
Tomohiko Yamamoto ◽  
Nobuchika Kawasaki ◽  
Tsutomu Hirotani ◽  
...  
Keyword(s):  
Fast Reactor ◽  
Static Loading ◽  
Restoring Force ◽  
Natural Period ◽  
Rubber Bearing ◽  
Safety Margins ◽  
Ultimate Properties ◽  
Loading Tests ◽  
Rubber Bearings ◽  
Force Characteristics

This paper describes the results of static loading tests using a half-scale thick rubber bearing to investigate ultimate properties application for a Sodium-cooled-Fast-Reactor (SFR). The thick rubber bearing, which has a rubber layer roughly three times thicker in comparison with conventional rubber bearings, has been developed by the authors to ensure seismic safety margins for components installed in the reactor building, and to reduce seismic response in the vertical direction as well as horizontal direction. The thick rubber bearings, 1600 mm in diameter at full scale, have been designed to provide a rated load of about 10000 kN with a horizontal natural period of 3.4 s and a vertical natural period of about 0.133 s. The fundamental restoring-force characteristics of the thick rubber bearings has been already cleared through the static loading tests using a half-scale thick rubber bearing, 800 mm in diameter. However, variations of the restoring force characteristics and ultimate properties have not been obtained yet. These validations are essential from the point of view of Probabilistic Risk Assessment (PRA) for a base isolated nuclear plant as well as to verify the structural integrity of the thick rubber bearing. The purpose of this paper is to indicate the variation of the stiffness and damping ratio concerning restoring force characteristics and the breaking strain or stress as ultimate properties through static loading tests using the half-scale thick rubber bearings.

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.

Research and Development of Rubber Bearings for Sodium-Cooled Fast Reactor: Ultimate Properties of Half-Scale Thick Rubber Bearings Based on Breaking Tests

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Tsuyoshi Fukasawa ◽  
Shigeki Okamura ◽  
Tomohiko Yamamoto ◽  
Nobuchika Kawasaki ◽  
Tsutomu Hirotani ◽  
...  
Keyword(s):  
Fast Reactor ◽  
Static Loading ◽  
Restoring Force ◽  
Natural Period ◽  
Safety Margins ◽  
Ultimate Properties ◽  
Loading Tests ◽  
Rubber Bearings ◽  
Breaking Points ◽  
Force Characteristics

This paper describes the results of static loading tests using a half-scale thick rubber bearing to investigate ultimate properties application for a sodium-cooled-fast-reactor (SFR). Thick rubber bearings which have a rubber layer that is roughly two times thicker in comparison with existing rubber bearings have been developed by the authors to ensure seismic safety margins for components installed in the reactor building, and to reduce the seismic response in the vertical direction as well as the horizontal direction. The thick rubber bearings, 1600 mm in diameter at the full scale, have been designed to provide a rated load of about 10,000 kN, at the compressive stress of 5.0 MPa, with a horizontal natural period of 3.4 s and a vertical natural period of about 0.133 s. The restoring-force characteristics, including variations, and breaking points, for the thick rubber bearings have not been cleared yet. These validations are essential from the point of view of probabilistic risk assessment (PRA) for a base-isolated nuclear plant as well as a verification of the structural integrity of the thick rubber bearings. The purpose of this paper is to indicate the variation of the stiffness and damping ratios for restoring force characteristics, and the breaking strain or stress, as ultimate properties through static loading tests using half-scale thick rubber bearings. In addition, an analytical model for the thick rubber bearings which is able to express the nonlinear restoring force, including the breaking points, is presented.

Design of Shape Memory Alloy Damper for Base Isolated Structure

1997 ◽  
Author(s):  
Krzysztof Wilde ◽  
Paolo Gardoni ◽  
Yozo Fujino ◽  
Stefano Besseghini
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Base Isolation ◽  
Hysteretic Behavior ◽  
Isolation System ◽  
Rubber Bearing ◽  
Laminated Rubber Bearing ◽  
Base Isolation System ◽  
Rubber Bearings ◽  
Smart Base Isolation

Abstract Base isolation provides a very effective passive method of protecting the structure from the hazards of earthquakes. The proposed isolation system combines the laminated rubber bearing with the device made of shape memory alloy (SMA). The smart base isolation uses hysteretic behavior of SMA to increase the structural damping of the structure and utilizes the different responses of the SMA at different levels of strain to control the displacements of the base isolation system at various excitation levels. The performance of the smart base isolation is compared with the performance of isolation by laminated rubber bearings to assess the benefits of additional SMA damper for isolation of three story building.

Development on Rubber Bearings for Sodium-Cooled Fast Reactor: Part 1 — Examination Plan

2015 ◽  
Author(s):  
Tomohiko Yamamoto ◽  
Nobuchika Kawasaki ◽  
Tsuyoshi Fukasawa ◽  
Shigeki Okamura ◽  
Takahiro Somaki ◽  
...  
Keyword(s):  
Mechanical Characteristic ◽  
Fast Reactor ◽  
Axial Loading ◽  
Scale Model ◽  
Preliminary Examination ◽  
Plant Life ◽  
Rubber Bearing ◽  
Laminated Rubber Bearing ◽  
Creep Characteristic ◽  
Rubber Bearings

This paper describes the past preliminary examination results and the new characteristic examination plans of the thick laminated rubber bearing for the application to Sodium-cooled Fast Reactor (SFR). The preliminary examination focusing on mechanical characteristics such as shear modulus with a 1/8-scale model (ϕ= 200 mm) and creep characteristics with a 1/13-scale model (ϕ= 120 mm) were carried out [1]. With the basic mechanical characteristic examination, the basic design formulas were temporarily confirmed. Furthermore, to establish the creep prediction formula, the creep characteristic examination has been carried out and the creep amount during the plant life has been approximately predicted. To obtain the mechanical properties of thick laminated rubber bearing with the scale-effect, the basic mechanical characteristic examination, including the ultimate behavior test, with the 1/2-scale model (ϕ= 800 mm) will be planned to confirm design margin with clarifying the ultimate limit curve under the bi-axial loading such as shear strain and the normal stress. Moreover, the deterioration promoted examination will be planned. The object of this examination is intended to grasp the degree of aging that may be caused by environmental effects during the plant life. By the accelerated deterioration examination results, the influence by aging on the mechanical characteristic and ultimate behavior of the laminated rubber bearing could be evaluated.

scholarly journals Evaluation of Seismic Performance Focusing on Increasing Response of Lead Rubber Bearing (LRB) and Over Strength of RC Pier During Earthquake

2020 ◽  
pp. 33-50
Author(s):  
Naito Nobuyuki ◽  
Park Kyeonghoon ◽  
Mazda Taiji ◽  
Uno Hiroshige ◽  
Kawakami Masahide
Keyword(s):  
Shear Strain ◽  
Seismic Performance ◽  
Elastic Behavior ◽  
Rubber Bearing ◽  
Lead Rubber Bearing ◽  
Lead Rubber Bearings ◽  
Laminated Rubber Bearing ◽  
Current Design ◽  
Rubber Bearings ◽  
Bearing Behavior

The characteristics of the seismic bearing change depending on various factors. When an earthquake occurs, the behavior of the bridge may differ from the values expected in the structural design. The shear deformation of the seismic bearing may increase, but it is difficult to reach the fracturede formation. This paper studied the effect of the stiffness due to various dependency and durability on Lead Rubber Bearings (LRB) and the over strength of bridge piers on the bearing behavior when an earthquake occurred. As a result, if the stiffness of LRB reduces within the criteria, seismic performance can be expected safety even if the shear strain designed in the current design is greater than the allowable shear strain. The reason is that the hardening phenomenon in the high strain region of the laminated rubber bearing suppresses the displacement. Also, since the seismic bridges with over strength of the piers have come near elastic behavior when an earthquake occurs, shear strain is easy to be large.

Development on Rubber Bearings for Sodium-Cooled Fast Reactor: Part 5 — Non-Linear Analytical Models for Thick Rubber Bearing

2017 ◽  
Author(s):  
Tsutomu Hirotani ◽  
Takahiro Mori ◽  
Tsuyoshi Fukasawa ◽  
Shigeki Okamura ◽  
Tomohiko Yamamoto ◽  
...  
Keyword(s):  
Vertical Direction ◽  
Analytical Models ◽  
Test Results ◽  
3D Fem ◽  
Restoring Force ◽  
Fem Model ◽  
Rubber Bearing ◽  
Non Linear ◽  
Rubber Bearings ◽  
Breaking Points

Application of seismic isolation system is essential to reduce the seismic force not only for the horizontal direction but also for vertical direction since the component installed to the Sodium-Cooled-Fast-Reactor (SFR) has thin-walled structures to reduce thermal stress. The authors have performed static loading tests using a half-scale thick rubber bearing to investigate ultimate properties include breaking, and confirmed that the thick rubber bearings have sufficient performance compared to the conventional thin rubber bearings. The present paper describes the evaluation of analytical models for the thick rubber bearing by following two approaches based on the obtained test results. a) Spring model Horizontal and vertical spring models, which are employed to the non-linear seismic response analysis, are compiled to examine applicability of conventional analytical model for thin rubber bearing. In addition, the horizontal and vertical spring models are modified, as a suitable non-linear analytical model for the thick rubber bearing. For the horizontal direction, hysteresis rules composed of multiple lines considering slip effect are modified to correspond to the hysteresis characteristics obtained test results. Hysteresis rules under vertical direction composed of multiple lines in consideration of effect on the shear strain due to horizontal seismic response is constructed. b) 3D FEM model The prediction methods of break strain for thin rubber bearings as the conventional rubber bearing have been examined, which have been proposed by the authors as 3D finite element analysis in consideration of the hyper elasticity. To improve suitable the above mentioned methods for the corresponding the restoring force characteristics for thick rubber bearing, 3D FEM model containing a higher-order elements was constructed to express the skeleton curve as restoring force characteristics up to the breaking points. The validity of the constructed 3D FEM model was investigated comparing breaking test results under horizontal and vertical direction. Consequently, the analytical results demonstrated that the skeleton curves up to the horizontal and vertical breaking points can express with constructed 3D FEM model. In addition, this paper describes the criteria with respect to the breaking strain by utilizing the analytical results.

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