DEVELOPMENT OF EVALUATION METHOD FOR SEISMIC ISOLATION SYSTEMS OF NUCLEAR POWER FACILITIES - BREAK TEST OF FULL-SCALE LEAD RUBBER BEARINGS FOR NUCLEAR FACILITIES, PART 2 ULTIMATE PROPERTIES OF LRB BASED ON BREAK TESTS -

摘要

To investigate the ultimate properties of lead rubber bearings (LRB), which were designed for applying base-isolated nuclear power plants (NPPs), static shear break tests and tensile break tests were conducted for full-scale LRB with 1600 mm in diameter and for its half-scale LRB. A horizontal load was applied up to the shear break point with several constant axial loads in the shear break test. A tensile load was applied up to the tensile break point with and without offset shear deformations in the tensile break test. This paper presents the load-deformation relationship of the LRB obtained in the break tests. Based on the test results, horizontal and tensional linear limits of the LRB were evaluated to contribute to the design of base-isolated NPPs. In addition, the validity of the hardening stiffness model of the LRB, which was used for earthquake response analysis, was examined by comparing the model to the test results. Finally, the results of the friction tests conducted after the break tests using broken LRB specimens are shown. Horizontal hysteresis curves for three identical full-scale LRB specimens under the design compressive stress showed almost the same curves up to the shear break and the obtained shear-breaking strains were around 450%, which indicate small variations in the horizontal properties of the LRB under the same load condition. Tensile-breaking strains decreased with an increase in the offset shear deformations in the tensile break tests. The evaluated horizontal linear limit of strain was between 274% and 302%, and tensional linear limit of stress was between 1.0 MPa and 1.4 MPa.