Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities: Part 7 — Breaking Test Plan and Development of Test Machine for Full-Scale Lead Rubber Bearings

2014 ◽  
Author(s):  
Shinji Kosugi ◽  
Kenji Kanazawa ◽  
Hidekazu Tsudome ◽  
Nobuhisa Sato ◽  
Masakazu Jimbo ◽  
...  
Keyword(s):  
Nuclear Power ◽  
Seismic Isolation ◽  
Evaluation Method ◽  
Full Scale ◽  
Test Machine ◽  
Test Plan ◽  
Seismic Safety ◽  
Isolation Systems ◽  
Rubber Bearings ◽  
Seismic Isolation Systems

This paper is a part of the series “Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities.” This part presents a break test plan and development of a test machine for a full-scale lead rubber bearing (LRB). Application of seismic base-isolation systems using LRBs of 1600 mm in diameter to reactor building has been considered for the purpose of enhancing seismic safety. It is important to obtain the ultimate properties of isolators in order to estimate the seismic safety margin of seismic base-isolated structures against a beyond design-basis earthquake events. Recent studies reveal that the scaled effect appears on the ultimate properties of seismic rubber bearings. However, because of the limitation of the loading capabilities of loading machines, the ultimate property of such a large scale LRBs has not been confirmed. In this study, the break tests for LRBs of 1600 mm in diameter is planned on the basis of estimation that refers to previous studies on break tests for small-scale LRBs and natural rubber bearings. The world-largest class test machine is designed and constructed to conduct static break tests for the full-scale LRBs. Furthermore, the performance of the test machine is evaluated from test results including those for break tests.

Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities: Part 9 — Ultimate Properties of Full-Scale Lead Rubber Bearings Based on Breaking Test

2014 ◽  
Author(s):  
Takafumi Hiraki ◽  
Seiji Nagata ◽  
Kenji Kanazawa ◽  
Tetsuo Imaoka ◽  
Takashi Nakayama ◽  
...  
Keyword(s):  
Nuclear Power ◽  
Seismic Isolation ◽  
Evaluation Method ◽  
Failure Modes ◽  
Full Scale ◽  
Break Surface ◽  
Lead Rubber Bearings ◽  
Isolation Systems ◽  
Rubber Bearings ◽  
Seismic Isolation Systems

This paper presents a part of “Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities”. Ultimate behavior and failure modes of full-scale Lead Rubber Bearings (LRBs) of 1600mm diameter were described herein based on a series of the break tests which conducted on 11 LRBs to obtain a break surface. The shear break tests were monotonically conducted on 3 full-scale LRBs under various axial stresses. Then the monotonic tensile break tests were performed on 5 full-scale LRBs with or without constant offset shear strain. In addition, 3 half-scale LRBs of 800mm diameter were also tested to study the size effect and the ultimate shear behavior in significantly high compression. In the evaluation on the test results, the ultimate strain and stress were firstly summarized to define a break surface for the real-scale LRBs. Then the LRBs broken in the testing were carefully observed to evaluate their failure modes. It was found that the full-scale LRBs exhibited good seismic performance in horizontal ductility capacity and vertical load carrying capacity. It seems that the ultimate properties and the failure modes were basically less affected by the scale of the models.

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.

Effect of Nonlinearity of Rubber Bearing on a Seismic Isolated Structure Considering Their Layout

2014 ◽  
Author(s):  
Sebastien Chirez ◽  
Satoshi Fujita ◽  
Keisuke Minagawa
Keyword(s):  
Nuclear Power ◽  
Seismic Isolation ◽  
Power Plants ◽  
Response Analysis ◽  
Seismic Safety ◽  
Rubber Bearing ◽  
Isolation Systems ◽  
Set Up ◽  
Rubber Bearings ◽  
Seismic Isolation Systems

In Japan, in order to ensure seismic safety requirements for buildings such as hospitals, nuclear power plants and communication centers for instance, seismic isolation systems have been developed. The most widely used technologies are rubber bearings and oil dampers, which can enhance the protection of equipment or machinery set up in those buildings. However, the isolation performance may face difficulties in case of huge earthquakes because of the nonlinearity of rubber bearings. In a former study of our laboratory, an earthquake response analysis based on the Runge-Kutta-Gill’s method had been carried out in order to assess the behavior of the rubber bearings[1]. In this paper, we use the same method but for further accurate and more realistic simulations, the analytical model has been improved in order to assess the response of rubber bearings depending on their layout when we consider the rocking of the building.

Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities: Part 8 — Fundamental Properties of Full-Scale Lead Rubber Bearings Based on Breaking Test

2014 ◽  
Author(s):  
Nobuhisa Sato ◽  
Takashi Nakayama ◽  
Takashi Kaneko ◽  
Seiji Nagata ◽  
Tetsuo Imaoka ◽  
...  
Keyword(s):  
Nuclear Power ◽  
Seismic Isolation ◽  
Evaluation Method ◽  
Axial Stress ◽  
Tensile Force ◽  
Full Scale ◽  
Fundamental Properties ◽  
Lead Rubber Bearings ◽  
Rubber Bearings ◽  
Seismic Isolation Systems

This paper provides a part of the series “Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities.” This part shows the fundamental properties of full-scale lead rubber bearings with 1600 mm diameter based on break tests. The following results are mainly obtained. One: The deformations and the acting loads of the full-scale specimens were accurately obtained up to break by the measurement system for the break tests. Two: The fundamental properties for the full-scale lead rubber bearings with a large-diameter lead plug were obtained by the basic property tests. The load-displacement relations were stable and similar basic properties were obtained among the specimens. Three: The result of shear break tests showed that the hardening property of the specimens had a certain harmony with the hardening stiffness model which was used in the seismic response analysis to investigate the safety margin for severe earthquakes beyond design basis earthquakes of nuclear power facilities. The effect of axial pressure on hardening property was not specifically observed. The evaluated linear strain limit was larger than 250% for every specimen. Four: The softening property of the specimens was obtained from the tensile break tests. The axial stress of tensile yield was approx. 1.4 MPa and the axial stress did not show any negative gradient at least up to approx. 10% axial strain after the tensile yield even with offset shear strains. Five: The tensile force acting on the bolts which secure the specimen to the testing machine was lower than the estimated tensile force at shear break, which indicates tensile force was conservatively calculated to maintain safety in the design for foundation of lead rubber bearings.

Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities: Part 6 — Scaled Tests to Obtain Basic Characteristics of Lead Rubber Bearing

2014 ◽  
Author(s):  
Tsutomu Hirotani ◽  
Ryota Takahama ◽  
Masaki Yukawa ◽  
Hiroshi Hibino ◽  
Yuji Aikawa ◽  
...  
Keyword(s):  
Nuclear Power ◽  
Seismic Isolation ◽  
Evaluation Method ◽  
Loading Test ◽  
Rubber Bearing ◽  
Lead Rubber Bearing ◽  
Basic Characteristics ◽  
Isolation Systems ◽  
Seismic Isolation Systems ◽  
Hysteresis Characteristics

This paper provides a series comprising the “Development of Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities”. Part 6 presents scaled tests for Lead Rubber Bearing (LRB) newly developed for this project. Following tests are performed to obtain the basic characteristics of LRB,. (1) Horizontal and Vertical Simultaneous Loading Test: LRBs with diameter of 250mm are tested dynamically under simultaneous axial and lateral loading. The hysteresis characteristics is not changed under compressive load although it is changed under tensile load. (2) Basic Break Test: LRBs with a diameter of 800mm are tested statically under various combinations of axial and lateral forces. The hysteresis characteristics model of LRB is determined by this test. It is confirmed that the breaking strain of LRB under compression load exceeds 450%. (3) Horizontal Hardening and Vertical Softening Test: For LRBs with a diameter of 1200 mm, 75% scale of actual LRB are tested statically for horizontal hardening and vertical softening regions. It is confirmed that the hysteresis model which is developed by smaller LRBs is applicable to these large scale models.

Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities: Part 2 — Application of CCFS Method to the Multiply Supported Systems

2014 ◽  
Author(s):  
Koichi Tai ◽  
Keisuke Sasajima ◽  
Shunsuke Fukushima ◽  
Noriyuki Takamura ◽  
Shigenobu Onishi
Keyword(s):  
Power Plant ◽  
Nuclear Power ◽  
Seismic Isolation ◽  
Evaluation Method ◽  
Time History ◽  
Piping System ◽  
History Analysis ◽  
Piping Systems ◽  
Isolation Systems ◽  
Seismic Isolation Systems

This paper provides a part of series of “Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities”. Paper is focused on the seismic evaluation method of the multiply supported systems, as the one of the design methodology adopted in the equipment and piping system of the seismic isolated nuclear power plant in Japan. Many of the piping systems are multiply supported over different floor levels in the reactor building, and some of the piping systems are carried over to the adjacent building. Although Independent Support Motion (ISM) method has been widely applied in such a multiply supported seismic design of nuclear power plant, it is noted that the shortcoming of ignoring correlations between each excitations is frequently misleaded to the over-estimated design. Application of Cross-oscillator, Cross-Floor response Spectrum (CCFS) method, proposed by A. Asfura and A. D. Kiureghian[1] shall be considered to be the excellent solution to the problems as mentioned above. So, we have introduced the algorithm of CCFS method to the FEM program. The seismic responses of the benchmark model of multiply supported piping system are evaluated under various combination methods of ISM and CCFS, comparing to the exact solutions of Time History analysis method. As the result, it is demonstrated that the CCFS method shows excellent agreement to the responses of Time History analysis, and the CCFS method shall be one of the effective and practical design method of multiply supported systems.

Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities: Part 3 — Seismic Response of Crossover Piping for Seismic Isolation System

2014 ◽  
Author(s):  
Akihito Otani ◽  
Teruyoshi Otoyo ◽  
Hideo Hirai ◽  
Hirohide Iiizumi ◽  
Hiroshi Shimizu ◽  
...  
Keyword(s):  
Seismic Response ◽  
Nuclear Power ◽  
Seismic Isolation ◽  
Evaluation Method ◽  
Response Spectrum ◽  
Time History ◽  
Response Analysis ◽  
Isolation System ◽  
Isolation Systems ◽  
Seismic Isolation Systems

This paper, which is part of the series entitled “Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities”, shows the linear seismic response of crossover piping installed in a seismically isolated plant. The crossover piping, supported by both isolated and non-isolated buildings, deforms with large relative displacement between the two buildings and the seismic response of the crossover piping is caused by two different seismic excitations from the buildings. A flexible and robust structure is needed for the high-pressure crossover piping. In this study, shaking tests on a 1/10 scale piping model and FEM analyses were performed to investigate the seismic response of the crossover piping which was excited and deformed by two different seismic motions under isolated and non-isolated conditions. Specifically, as linear response analysis of the crossover piping, modal time-history analysis and response spectrum analysis with multiple excitations were carried out and the applicability of the analyses was confirmed. Moreover, the seismic response of actual crossover piping was estimated and the feasibility was evaluated.

Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities: Part 4 — Failure Behavior of Crossover Piping for Seismic Isolation System

2014 ◽  
Author(s):  
Teruyoshi Otoyo ◽  
Akihito Otani ◽  
Shunsuke Fukushima ◽  
Masakazu Jimbo ◽  
Tomofumi Yamamoto ◽  
...  
Keyword(s):  
Nuclear Power ◽  
Seismic Isolation ◽  
Evaluation Method ◽  
Low Cycle Fatigue ◽  
Response Analysis ◽  
Failure Behavior ◽  
Isolation System ◽  
Isolation Systems ◽  
Seismic Isolation Systems ◽  
Failure Location

This paper provides a part of the series titled “Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities”. This part shows the failure behavior of crossover piping installed in a seismic isolated plant. The considered crossover piping is supported on one side by an isolated building and by a non-isolated building on the other side. During an earthquake, the piping structure is deformed due to the large relative displacements between the two buildings and at the same time excited by the different building seismic responses. Therefore, the high-pressure crossover piping structure requires both flexibility and strength. In this study, 1/10 scaled shaking tests and FEM analyses have been performed to investigate the failure behavior of the crossover piping, where both seismic motions and excitations have been taken into account. It was confirmed that the failure occurs at the piping elbow through low cycle fatigue. Moreover, the results of the elastic-plastic response analysis, which simulates an extreme level of excitation corresponding to more than three times the design level, are in good agreement with the test results. The simulation also succeeded in predicting the experimental failure location.

Response Analysis of a Seismic Isolated Structure Considering the Nonlinearity of the Rubber Bearings

2013 ◽  
Author(s):  
Alexandre Borsoi ◽  
Satoshi Fujita ◽  
Keisuke Minagawa
Keyword(s):  
Nuclear Power ◽  
Seismic Isolation ◽  
Power Plants ◽  
Industrial Structure ◽  
Response Analysis ◽  
Vertical Load ◽  
Restoring Force ◽  
Seismic Safety ◽  
Rubber Bearings ◽  
Seismic Isolation Systems

In Japan, the application of seismic isolation systems using rubber bearings to industrial structure and new generation Nuclear Power Plants have been considered in order to enhance seismic safety. However, the isolation performance will decline in case of huge earthquakes, because of the nonlinearity of both horizontal and vertical restoring characteristics of the rubber bearings. The horizontal restoring force has a hardening characteristic and the vertical restoring force has a softening characteristic. In addition, the horizontal nonlinearity depends on vertical load, so the interaction between the horizontal and vertical response is important. Consequently, in this paper, the analysis of the nonlinearity of the rubber bearings and the coupling between those two directions will be carried out. Then, after comparing these two approaches, the utility of considering this dependency will be estimated. To do so, a simulation program, based on the Runge-Kutta-Gill’s method has been developed in order to evaluate the seismic response of the isolated structure composed of rubber bearings and oil dampers. The nonlinearity of the rubber bearings is considered, and the coupling of the vertical load and the horizontal hardening has been implemented.

Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities: Part 5 — Fatigue Test of the Crossover Piping

2014 ◽  
Author(s):  
Kotoyo Mizuno ◽  
Hiroshi Shimizu ◽  
Masakazu Jimbo ◽  
Naohiko Oritani ◽  
Shigenobu Onishi
Keyword(s):  
Fatigue Life ◽  
Fatigue Test ◽  
Nuclear Power ◽  
Seismic Isolation ◽  
Evaluation Method ◽  
Failure Modes ◽  
Structural Integrity ◽  
Relative Displacement ◽  
Isolation Systems ◽  
Seismic Isolation Systems

This paper provides a part of the series of “Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities”. It is assumed the main steam crossover piping is damaged by the ratcheting deformation based on the relative displacement and the inertia load by the earthquake between the buildings and the internal pressure. This part shows a low cycle ratcheting fatigue test using the scaling model under the combined loadings based on the relative displacement and the inertia load by the earthquake between the buildings and analyses were performed to confirm the failure modes and the fatigue life of the pipe elbow for the fatigue damage of the long-period ground motion. As a result, the fatigue life under combined loads was sufficiently higher than the design criteria and analyses are good match with the test results. So, it confirmed the structural integrity of the crossover piping.

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