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

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.

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Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities: Part 11 — Improvement of the Seismic Isolator Design Method

Volume 8: Seismic Engineering ◽

10.1115/pvp2014-29000 ◽

2014 ◽

Author(s):

Yuji Aikawa ◽

Hiroshi Hibino ◽

Yoshitaka Takeuchi ◽

Shingo Asahara ◽

Hideo Hirai ◽

...

Keyword(s):

Nuclear Power ◽

Seismic Isolation ◽

Evaluation Method ◽

Design Method ◽

Axial Stress ◽

Seismic Isolator ◽

Rubber Bearing ◽

Laminated Rubber Bearing ◽

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”. This part shows improvements of seismic isolator design method applied to nuclear power facilities. The proposed improvement design methods consist of the following two items. One is an improvement of design method for axial stress in a laminated rubber bearing. Largely different natural frequency in vertical and horizontal direction of the seismic isolator may need a special consideration to combine the design seismic loads in different directions. Therefore isolator’s behavior under multiple direction earthquake is studied, and an improved design method is proposed in the axial stress in a laminated rubber bearing. The other is a reasonable design method for seismic isolator joints. A seismic isolator joint is considered to be one of the key factors for assuring seismic integrity of the seismic isolation system for nuclear power facilities. As a series of design method of seismic isolators, evaluation method of axial force of anchor bolts, among various parts of joints, under design level seismic load is studied and improved method is proposed to confirm the structural behavior for a better performance of the system.

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

Volume 8: Seismic Engineering ◽

10.1115/pvp2014-28999 ◽

2014 ◽

Cited By ~ 1

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.

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

Volume 8: Seismic Engineering ◽

10.1115/pvp2014-29012 ◽

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.

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

Volume 8: Seismic Engineering ◽

10.1115/pvp2014-29011 ◽

2014 ◽

Cited By ~ 1

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.

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

Volume 8: Seismic Engineering ◽

10.1115/pvp2014-29032 ◽

2014 ◽

Cited By ~ 2

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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Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities: Part 10 — Evaluation of Seismic Isolator Design

Volume 8: Seismic Engineering ◽

10.1115/pvp2014-29040 ◽

2014 ◽

Cited By ~ 3

Author(s):

Hiroyuki Asano ◽

Tsutomu Hirotani ◽

Takashi Nakayama ◽

Takemi Norimono ◽

Yuji Aikawa ◽

...

Keyword(s):

Nuclear Power ◽

Seismic Isolation ◽

Power Plants ◽

Evaluation Method ◽

Large Diameter ◽

Seismic Isolator ◽

Long Duration ◽

Seismically Isolated ◽

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”. This part shows an evaluation of seismic isolator design established in this project where several methods are newly developed. The major four accomplishments are as follows. One: establishment of design earthquake specially considered for seismically isolated nuclear power facilities. The design earthquakes are made to fit multiple target spectra with different damping factors considering a building, equipment and seismic isolators for more precise response analyses. Two: design and development of a high-performance seismic isolator. Against the large design earthquakes, a seismic isolator is newly developed which has a large diameter lead plug for more damping; the isolators were actually manufactured and tested. Three: seismic response analyses for seismically isolated nuclear power plants. Light water reactors are designed where the structural characteristics of the seismic isolation system is reflected. Four: evaluation of thermal effects on seismic isolators by a long-duration earthquake. Considering a long-duration earthquake, the heat generation phenomenon in the lead plug is analytically evaluated to ensure the lead plug’s damping performance. By introducing these accomplishments, the realistic design of a seismically isolated nuclear power plant is achieved.

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