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.

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.

Research and Development of Three-Dimensional Isolation System for Sodium-Cooled Fast Reactor: Part 2 — Details of Characteristics for Disc Springs and Oil Dampers on Basis of Full-Scale Loading Tests

2018 ◽  
Author(s):  
Takahiro Somaki ◽  
Tsuyoshi Fukasawa ◽  
Takayuki Miyagawa ◽  
Tomohiko Yamamoto ◽  
Yoshifumi Hibako ◽  
...  
Keyword(s):  
Seismic Response ◽  
Analytical Model ◽  
Fast Reactor ◽  
Three Dimensional ◽  
Damping Capacity ◽  
Restoring Force ◽  
Isolation System ◽  
Loading Tests ◽  
Rubber Bearings ◽  
Force Characteristics

Being compatible with the seismic and thermal loads for the large Sodium-cooled Fast Reactor (SFR), the three-dimensional isolation system is inevitable technology. The three-dimensional isolation system consists of the thick rubber bearings, the disc springs and the oil dampers. Since the isolation performances on the rubber bearings in the horizontal direction have been revealed by the previous studies [1], the vertical isolation performance and characteristics such as restoring force and damping performance should be clarified by loading tests to build the analytical model. This paper presents these fundamental vertical isolation characteristics obtained by loading tests with full-scaled disc springs and oil dampers. The disc springs as the vertical restoring forces have 700 mm in external diameter and 34 mm in thickness. The oil dampers have the maximum damping force of 2,000 kN at the velocity of 0.25 m/s. The disc spring is one of the largest size, and the oil damper is one of the largest damping capacity in Japan. The static loading tests such as incremental cyclic loadings under the supporting load were conducted to investigate the restoring force characteristics for the disc springs. The dynamic loading using sinusoidal waves with varied input frequencies or the seismic response waves obtained by seismic response analysis were conducted to investigate the damping performance for the oil dampers. The applicability of the design method and the analytical model for disc springs and oil dampers were demonstrated by the restoring force characteristics obtained from tests. It should be noted, this paper is in series from Part 1.

Development on Rubber Bearings for Sodium-Cooled Fast Reactor: Part 2 — Fundamental Characteristics of Half-Scale Rubber Bearings Based on Static Test

2015 ◽  
Author(s):  
Tsuyoshi Fukasawa ◽  
Shigeki Okamura ◽  
Tomohiko Yamamoto ◽  
Nobuchika Kawasaki ◽  
Takahiro Somaki ◽  
...  
Keyword(s):  
Fast Reactor ◽  
Static Loading ◽  
Seismic Isolation ◽  
Linear Strain ◽  
Isolation System ◽  
Rubber Bearing ◽  
Strain Limit ◽  
Seismic Force ◽  
Loading Tests ◽  
Rubber Bearings

This paper described the results of the static loading tests using a half-scale thick rubber bearing to investigate the fundamental characteristics such as horizontal and vertical restoring force of a rubber bearing applied to a Sodium-cooled-Fast-Reactor (SFR). Since the SFR has thin-walled component structures, a seismic isolation system is employed to mitigate the seismic force. A rubber bearing with thick rubber layers is used for the seismic isolation system applied to the SFR, it was developed aiming for isolation of not only horizontal response acceleration, but also vertical response acceleration. The thick rubber bearing of 1600 mm in diameter full-scale was designed to provide about a 10000 kN rated load with a horizontal natural period of 3.4 s and a vertical one of 0.125 s. Moreover, a linear strain limit of the thick rubber bearing was designed to accept a horizontal displacement of 700 mm or more in order to ensure a double safety margin for response displacements against a design basis ground motion. The static loading tests were performed using a half-scale thick rubber bearing with a diameter of 800 mm to investigate the horizontal/vertical stiffness, damping ratio, a linear strain limit in horizontal direction and a tensile yield stress in the vertical direction. The fundamental characteristic of rubber bearings employed to the SFR and the validity of a design formula became clear through the static loading tests.

Development on Rubber Bearings for Sodium-Cooled Fast Reactor: Part 4 — Aging Properties of a Half Scale Thick Rubber Bearings Based on Breaking Test

2016 ◽  
Author(s):  
Tomoyoshi Watakabe ◽  
Tomohiko Yamamoto ◽  
Tsuyoshi Fukasawa ◽  
Shigeki Okamura ◽  
Takahiro Somaki ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fast Reactor ◽  
Seismic Isolation ◽  
Hysteresis Loops ◽  
Natural Period ◽  
Isolation System ◽  
Rubber Bearing ◽  
Aging Properties ◽  
Rubber Bearings ◽  
Effects Of Aging

A seismic isolation system composed of a thick rubber bearing and an oil damper has been developed for Sodium-Cooled Fast Reactor. One of the advantages of the isolation system is the use of thick rubber bearings to ensure the longer vertical natural period of a plant, thereby mitigating seismic loads to mechanical components. Based on many previous studies, rubber bearing technology has progressed, but test data regarding the effect of aging is not sufficient. Moreover, there is no data on the limits of linear strain and breaking behavior for thick rubber bearings after aging. This paper focused on the aging properties of thick rubber bearings, such as basic mechanical properties and ultimate strength. An aging test of thick rubber bearings was conducted using 1/2-scale (800mm diameter) and 1/8-scale (200mm diameter) rubber bearings. Aging of the rubber bearings was reproduced using thermal degradation, in which the target of aging periods were 30 and 60 years. The hysteresis loops of the thick rubber bearings after aging were obtained through horizontal and vertical static loading tests, and the effects of aging were evaluated by comparison with the initial mechanical properties. In addition, for the purpose of further research, the effect of scale by aging was clarified to compare the mechanical properties between the 1/2-scale and 1/8-scale rubber bearings.

Research and Development of Three-Dimensional Isolation System for Sodium-Cooled Fast Reactor: Part 3 — Characteristics for Elements on Basis of Half-Scale Loading Tests

2019 ◽  
Author(s):  
Takahiro Somaki ◽  
Tsuyoshi Fukasawa ◽  
Shigeki Okamura ◽  
Takayuki Miyagawa ◽  
Masato Uchita ◽  
...  
Keyword(s):  
Fast Reactor ◽  
Seismic Isolation ◽  
Design Method ◽  
Three Dimensional ◽  
Isolation System ◽  
Rubber Bearing ◽  
In Series ◽  
Loading Tests ◽  
Rubber Bearings ◽  
Disc Spring

Abstract The authors have been developing the three-dimensional isolation system for a Sodium-cooled Fast Reactor, and reported the details of characteristics of disc springs and vertical oil dampers on the basis of full-scale loading tests [1]. To clarify the fundamental characteristics of the three-dimensional isolation system, the loading tests using a half-scale assembled specimen have been planned, which is composed of a rubber bearing, disc spring units, the horizontal supporting functions, the smoothly sliding elements, and the rotate restraint elements. This paper describes each characteristic of the rubber bearings, disc springs and sliding element before assembling a half-scale specimen of the three-dimensional seismic isolation system by the static or dynamic loading. The applicability of design method, the scaling effect in disc springs, and the dependence on the friction coefficient of the sliding elements were investigated and confirmed. Additionally, the method of minimizing the variation of force-displacement relationships between four disc spring units, each of which has the three disc springs stacked in parallel and six disc springs stacked in series, was studied. It should be noted that this paper is in series from Part 2 [1] held on 2018PVP.

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.

Shaking Table Tests of Full Scale Base-Isolated Structures

2002 ◽  
Author(s):  
C. S. Tsai ◽  
B. J. Chen ◽  
T. C. Chiang
Keyword(s):  
Structural Control ◽  
Control Strategies ◽  
Steel Structure ◽  
Seismic Energy ◽  
Full Scale ◽  
Shaking Table ◽  
Shaking Table Tests ◽  
Natural Period ◽  
Rubber Bearing ◽  
Rubber Bearings

Conventional earthquake resistant designs depend on strengthen and ductility of the structural components to resist induced forces and to dissipate seismic energy. However, this can produce permanent damage to the joints as well as the larger interstory displacements. In recently years, many studies on structural control strategies and devices have been developed and applied in U. S. A., Europe, Japan, and New Zealand. The rubber bearing belongs to one kind of the earthquake-proof ideas of structural control technologies. The installation of rubber bearings can lengthen the natural period of a building and simultaneously reduce the earthquake-induced energy trying to impart to the building. They can reduce the magnitude of the earthquake-induced forces and consequently reduce damage to the structures and its contents, and reduce danger to its occupants. This paper is aimed at studying the mechanical behavior of the stirrup rubber bearings (SRB) and evaluating the feasibility of the buildings equipped with the stirrup rubber bearings. Furthermore, uniaxial, biaxial, and triaxial shaking table tests are conducted to study the seismic response of a full-scale three-story isolated steel structure. Experimental results indicate that the stirrup rubber bearings possess higher damping ratios at higher strains, and that the stirrup rubber bearings provide good protection for structures. It has been proved through the full-scale tests on shaking table that the stirrup rubber bearing is a very promising tool to enhance the seismic resistibility of structures.

Derailment of trains moving on lead rubber bearing bridges under seismic loads

2020 ◽  
Vol 26 (19-20) ◽  
pp. 1646-1655
Author(s):  
Shen-Haw Ju
Keyword(s):  
Finite Element ◽  
Seismic Loads ◽  
Base Shear ◽  
Natural Period ◽  
Train Derailment ◽  
Rubber Bearing ◽  
Lead Rubber Bearing ◽  
Lead Rubber Bearings ◽  
Dominant Period ◽  
Rubber Bearings

This study investigates the derailment of trains moving on bridges with lead rubber bearings. A moving wheel/rail axis element that couples two wheels and rails together is first developed to generate a train finite element model with 12 cars, while the sliding, sticking, and separation modes of the wheels and rails are accurately simulated. The finite element results indicate that the base shear of the bridge with lead rubber bearings is much smaller than that without lead rubber bearings. Similar to the base shear, the train derailment coefficients for the bridge with lead rubber bearings are much smaller than those without lead rubber bearings because yield lead rubber bearings during large seismic loads can change the bridge natural frequency to avoid resonance. For earthquakes with a very long dominant period, the lead rubber bearing effect to reduce the train derailment may not be obvious because the natural period of the bridge due to the full yield of lead rubber bearings can approach the dominant period of the earthquake.

Analysis and Experiment on the Effect of Seismic Protection of Buildings by High Damping Rubber Bearings

2004 ◽  
Author(s):  
Jun-Ping Pu ◽  
C. S. Tsai ◽  
Jian-Fa Huang ◽  
Bo-Jen Chen ◽  
Yao-Min Fang
Keyword(s):  
Earthquake Engineering ◽  
Base Isolation ◽  
Steel Structure ◽  
Shaking Table ◽  
Natural Period ◽  
Rubber Bearing ◽  
High Damping Rubber Bearings ◽  
High Damping Rubber Bearing ◽  
High Damping Rubber ◽  
Rubber Bearings

In recent years, many studies on base isolation strategies and devices have been developed and applied in U. S. A., Europe, Japan, and New Zealand. The high damping rubber bearing belongs to one kind of the earthquake-proof ideas of base isolation technologies. The installation of high damping rubber bearings can lengthen the natural period of a building and simultaneously reduce the earthquake-induced energy trying to impart to the building. The objective of this paper is to investigate the base isolation effect of high damping rubber bearings. The uniaxial, biaxial, and triaxial shaking table tests were performed to study the seismic behavior of a 0.4-scale three-story isolated steel structure in the National Center for Research on Earthquake Engineering in Taiwan. The experimental and analytical results show that the nonlinear mechanical characteristics of the high damping rubber bearings can be reasonably simulated.

Research and Development of Three-Dimensional Isolation System for Sodium-Cooled Fast Reactor: Part 1 — Proposal of Analytical Models Based on Loading Tests

2018 ◽  
Author(s):  
Tsuyoshi Fukasawa ◽  
Shigeki Okamura ◽  
Takahiro Somaki ◽  
Takayuki Miyagawa ◽  
Masato Uchita ◽  
...  
Keyword(s):  
Seismic Response ◽  
Analytical Model ◽  
Three Dimensional ◽  
Analytical Models ◽  
Response Analysis ◽  
Seismic Response Analysis ◽  
Natural Period ◽  
Isolation System ◽  
Loading Tests ◽  
Rubber Bearings

This paper describes that the analytical model for the three-dimensional isolation system [1], which consists of thick rubber bearings, disc springs and oil dampers, is created through loading tests. The new-type analytical models of each element are proposed to improve the prediction accuracy of the seismic response analysis. The concept of the three-dimensional isolation system has been proposed to ensure the structural integrity for large reactor vessels. The primary specifications of the three-dimensional isolation system are a horizontal natural period of 3.4 s and a vertical natural period of 0.33 s. The investigations of horizontal isolation performances have been conducted for the various types of isolation devices, beginning with rubber bearings, whereas the previous studies focused on the vertical isolation performances are only a few. Hence, isolation characteristics, such as restoring force and damping force, should be clarified by loading tests using vertical seismic isolation elements, and analytical model to assess the seismic response should be identified on the basis of the loading test results. This paper presents a new analytical model with providing of the differential equations to improve the prediction accuracy and demonstrates the seismic performance, including beyond-design-basis ground motion, for the three-dimensional isolation system by the seismic response analysis.

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