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.

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 5 — Isolation Performance Applied to Reactor Building

2020 ◽  
Author(s):  
Takahiro Somaki ◽  
Tsuyoshi Fukasawa ◽  
Shigeki Okamura ◽  
Takayuki Miyagawa ◽  
Masato Uchita ◽  
...  
Keyword(s):  
Fast Reactor ◽  
Analytical Modeling ◽  
Three Dimensional ◽  
Response Spectra ◽  
Scale Model ◽  
Isolation System ◽  
Rubber Bearing ◽  
Reactor Building ◽  
Isolation Performance ◽  
Disc Spring

Abstract This paper presents the isolation performance of a three-dimensional base isolated Sodium-cooled Fast Reactor building. The three-dimensional isolation system consists of rubber bearing with the horizontal oil damper for the horizontal isolation system and disc spring units with vertical oil dampers for the vertical one, where the vertical one is set under the horizontal one to be arranged in series. These elements excepting the horizontal oil damper have been developed for the three-dimensional isolation system through the static or the dynamic loading tests using a full scale or a half scale model. Regarding the horizontal oil damper which is necessary for the three-dimensional isolation system as well as the horizontal isolation system, the details would be described in Part 6. The authors also have been tackled to create the analytical modeling for each element such as the disc spring units, vertical oil damper and rubber bearing. The previous studies from part 1 to part 4 clarified that the newly analytical model, each of which is defined by the differential equations, could accurately express relationships between the force and displacement of each element. To demonstrate the reduction effect (performance) of the seismic responses for the three-dimensional isolation system, the seismic response analyses using newly analytical modeling were performed for the Sodium-cooled Fast Reactor building that is modeled into the multi-degree-of-freedom-system. The isolation performance of the three-dimensional isolation system is verified through the floor response spectra evaluated at the position where the primary components are placed, in comparison with those by the conventional 2D horizontally isolation system using the rubber bearing without the vertical elements.

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 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 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.

scholarly journals Comparing Rubber Bearings and Eradi-Quake System for Seismic Isolation of Bridges

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5247
Author(s):  
Chang Beck Cho ◽  
Young Jin Kim ◽  
Won Jong Chin ◽  
Jin-Young Lee
Keyword(s):  
Seismic Isolation ◽  
New Technology ◽  
Isolation System ◽  
Seismic Safety ◽  
Response Characteristics ◽  
Rubber Bearing ◽  
Seismic Force ◽  
Isolation Systems ◽  
Rubber Bearings ◽  
Seismic Isolation Systems

Seismic isolation systems have been used worldwide in bridge structures to reduce vibration and avoid collapse. The seismic isolator, damper, and Shock Transmission Unit (SUT) are generally adopted in the seismic design of bridges to improve their seismic safety with economic efficiency. There are several seismic isolation systems, such as Natural Rubber Bearing (NRB), Lead Rubber Bearing (LRB), and the Eradi-Quake System (EQS). EQS as a new technology is expected to effectively reduce both seismic force and displacement, but there is still some need to verify whether it might provide an economical and practical strategy for a bridge isolation system. Moreover, it is important to guarantee consistent performance of the isolators by quality control. A comparative evaluation of the basic properties of the available seismic isolators is thus necessary to achieve a balance between cost-effectiveness and the desired performance of the bridge subjected to extreme loading. Accordingly, in this study, the seismic response characteristics of the seismic isolation systems for bridges were investigated by conducting compressive test and compressive-shear test on NRB, LRB, and EQS.

Research and Development of Three Dimensional Seismic Isolation System Utilized Coned-Disc-Springs With Rubber Bearings

2017 ◽  
Author(s):  
Takayuki Miyagawa ◽  
Tomoyoshi Watakabe ◽  
Tomohiko Yamamoto ◽  
Tsuyoshi Fukasawa ◽  
Shigeki Okamura
Keyword(s):  
Seismic Isolation ◽  
Three Dimensional ◽  
Safety Margin ◽  
Seismic Load ◽  
Isolation System ◽  
Seismic Safety ◽  
Track Record ◽  
Rocking Motion ◽  
Isolation Systems ◽  
Rubber Bearings

The seismic isolation system consisting of laminated rubber bearings is applied to development of the Sodium-cooled Fast Reactor (SFR) in Japan. While rubber bearings as horizontal isolation system have been expected to be ensured seismic safety margin of components installed in reactor building against horizontal seismic load, vertical isolation systems have been also studied in order to tolerate to the seismic load which has been increased steadily. In this paper, the three dimensional seismic isolation system by combining coned disc springs with rubber bearings is proposed as a concept which consists of isolation devices with abundant track record. Analytical study for this system results that the rocking motion can be suppressed by itself without any suppression system and that the mitigation of vertical response can be enough for buckling design of the reactor vessel simultaneously. In particular, it is important that the vertical natural frequency of system is within the range of 3Hz to 5Hz. Besides, layout, size and stacks of coned discs in the unit of system are studied in order to obtain suitable for specification to SFR buildings.

Required Properties of Seismic Isolation System for Nuclear Power Plants

2010 ◽  
Author(s):  
Satoshi Fujita ◽  
Keisuke Minagawa ◽  
Takeshi Kodaira
Keyword(s):  
Nuclear Power ◽  
Seismic Isolation ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Three Dimensional ◽  
Isolation System ◽  
Seismic Safety ◽  
Isolation Systems ◽  
Rubber Bearings ◽  
Seismic Isolation Systems

In Japan, applications of seismic isolation systems to new generation nuclear power plants and fast breeder reactors have been expected in order to enhance seismic safety. However there are lots of restrictions for design of isolation systems, such as strong design seismic wave, deformation of piping between an isolated structure and a non-isolated structure, and so on. In addition combination of horizontal and vertical isolation has possibility to cause rocking motion if a three-dimensional isolation system is applied. Therefore isolation systems should be designed properly. Moreover the design of seismic isolation system has to consider influence on inner equipment and piping. This paper describes investigation regarding required properties and performance of seismic isolation system for nuclear power plants. The investigation is carried out by numerical analysis. In the analysis, various isolation devices such as friction pendulum bearings and so on are applied as well as natural rubber bearings.

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