Recently, some weaknesses of a lead rubber bearing (LRB) have been identified such as excessive tensile stress at some basemat-edge isolators and degradation of lead plug damping performance by temperature rising due to responses during the large and long duration earthquakes. The degradation of lead plug damping performance has become a design factor and a concern with response evaluation method to consider the thermal effect to lead plug has been growing. In this paper, to study the degradation of lead plug damping performance, firstly loading tests (a multi-cyclic loading tests to get thermal conditions of the lead plug, and a horizontal/vertical directional loading tests to get mechanical behaviors of the LRB under multiple degree of freedom loading) for LRB specimens were performed, then an analysis program to simulate the tests are newly developed that are validated by comparing to the test results. By these tests and analyses, some new findings are given on heat generation characteristics of the lead plug along with its thermal boundary conditions. By checking the LRB performance after the loading tests, another finding is given that mechanical characteristics are almost recovered when the lead plug temperature is enough cooled even that was once heated up to 300 degrees Celsius.

This paper describes design formulas and creep characteristics for thick rubber bearing applied to the Sodium-cooled Fast Reactor, which are based on the static loading test and creep test using scale models. The thick rubber bearing, which has a rubber layer roughly two times thicker in comparison with conventional rubber bearings, has been developed by the authors to ensure seismic safety margins for components by reducing the seismic response for the reactor building in the horizontal direction and vertical direction. The static loading tests using a scale model with parameter of first shape factor were conducted to investigate the applicability of proposed design formulas. Moreover, an estimation of creep characteristics due to aging is important issue because the rubber layer of thick rubber bearing which satisfies the design requirement for SFR is larger than conventional rubber layer. The creep test was preformed to estimate the creep characteristics using a scale model. From the above results, the thick rubber bearing is sufficiently rational for use as isolation system for SFR.

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After the 2011 Off the Pacific Coast of Tohoku earthquake, it is a clear and present risk that future mega-thrust earthquakes may produce larger than expected displacement ground motions. We have to take measures to keep the displacement of base-isolated buildings within the designed clearance for such earthquakes. Therefore, we propose a fault-tolerant system to control the displacement of base-isolated buildings. The system uses a rugby-ball type device that changes kinetic energy into potential energy by rolling. We conducted shaking table experiments using a scaled steel frame model as base-isolated floors with JMA Kobe and JR Takatori waves observed during the 1995 Kobe Earthquake as input motions. We found that the upper frame of the model was raised 3 to 10 mm by the rotation of the fault-tolerant system and the horizontal displacement was decreased by 30 to 60 mm thanks to the system. Base-Isolation ,Clearance, Fault-tolerant produce larger than expected displacement ground motions. We have to take measures to keep the displacement of base-isolated buildings within the designed clearance for such earthquakes. Therefore, we propose a fault-tolerant system to control the displacement of base-isolated buildings. The system uses a rugby-ball type device that changes kinetic energy into potential energy by rolling. We conducted shaking table experiments using a scaled steel frame model as base-isolated floors with JMA Kobe and JR Takatori waves observed during the 1995 Kobe Earthquake as input motions. We found that the upper frame of the model was raised 3 to 10 mm by the rotation of the fault-tolerant system and the horizontal displacement was decreased by 30 to 60 mm thanks to the system. Keywords :

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