Development of Cable Reinforced 3-Dimensional Base Isolation Air Spring

Abstract

In Japan, the study on the development of a 3-dimensional base isolation system to be applied to a nuclear power plant, which requires supreme safety against severe earthquakes, has been carried out since 2000. An idea with the concept of a cable reinforced air spring was proposed as the 3-dimensional base isolation device. The dimension of the air spring applying to the actual power plant is 9 meters in the outer-diameter and 3.5 meters in height. The allowable half strokes are respectively 1.5 meters for the horizontal direction and 0.5 meters for the vertical directions. The supporting weight for a single device is 52MN, where the inner air pressure is about 1.2MPa. This device enables to realize three-dimensional base isolation with a single device, whose characteristics is a natural period of over 4 seconds in the horizontal direction and over 3 seconds in the vertical direction. Furthermore, this device does not require precision mechanical parts just common building materials, which are steel, cable wire, polyester fabric and a rubber sheet. Therefore, the construction cost for this device could be reduced effectively. In order to confirm the performance of the proposed device, experimental tests using the three dimensional shaking table were carried out on the proposed cable reinforced 3-dimensional base isolation air spring, whose outer diameter is 2 meters, being 1/4.5 scale of the actual size. The weight of approximately 392kN including a 4-story steel frame was loaded on the test specimen in order to create inner air pressure of 0.157MPa. As a result, the device was confirmed to function smoothly in three dimensions with natural periods of 1.8 seconds in the horizontal direction and 1.4 seconds in the vertical direction, and is considered that the proposed system can be applied to actual power plants.

Study on Three-Dimensional Seismic Isolation System for Next Generation Nuclear Power Plant: Independent Cable Reinforced Rolling-Seal Air Spring

“…The design values were evaluated in the formulas shown in eq. 1, (2). From the table, the design natural periods were well consistent with the values by test.…”

“…Therefore additional seismic supports for equipment/piping are required depending on the seismic conditions of the site. The primary phase in the 3D base isolation system development was already discussed Kageyama [2]. So, this paper deals with the demonstration phase of the 3D base isolation system development.…”

A Review of Seismic Isolation for Buildings: Historical Development and Research Needs

“…The rolling seal type air spring is a steel/concrete cylinder lowered into an air cavity and attached with a rolling rubber seal, and is configured in series with a laminated rubber bearing for horizontal isolation [101,102]. The cable reinforced air spring consists of an inner cylinder attached to the base and an outer cylinder attached to the structure separated by an air cavity bounded by a flexible rubber sheet [103,104]. The distance between the cylinders allows the device to move both horizontally and vertically and thus accommodate horizontal and vertical motion.…”

Recent Advances in Multi-Dimensional Vibration Mitigation Materials and Devices

“…Two parameters were considered in the design of the experiment, which decided the different contact of the horizontal and vertical loads. Kageyama et al (2003) studied the feasibility of applying an isolation device using three-dimensional cable reinforcing air spring to actual nuclear power plants, which shows that the air spring enables isolation in three dimensions with a single device, achieving a cost reduction. Zhao et al (2008) studied the valid performance of a newly multi-dimensional isolation using one main and eight auxiliary disk springs in parallel to modify the conventional rubber bearing in the vertical direction, which shows that this device can isolate three-dimensional earthquake energy remarkably.…”