Test study on dynamic characteristics of base-isolated structure on variable stiffness foundation

Here, based on influence laws of dynamic pore water pressure ratio change of saturated sandy soil foundation on foundation stiffness,a shaking table model test method for isolated structure on variable stiffness foundation was proposed by controlling compression ratio and strength of input ground motion duration. Combined with completed shaking table model tests of soil-pile-isolation structure series on different foundations, influence laws of foundation stiffness change on dynamic characteristics of base-isolated structure were analyzed. The results showed that with increase in relative stiffness ratio of structure-soil body, the first order natural frequency of base-isolated structure on variable stiffness foundation decreases, but system damping ratio increases obviously, especially, the isolation efficiency of isolation layer decreases obviously ; relative stiffness ratio of structure-soil body on variable stiffness foundation significantly affects story acceleration responses and inter-story displacement responses of isolation structure, the larger the relative stiffness ratio of structure-soil body under strong earthquakes, the more significant the increases in story acceleration responses and inter-story displacement responses of isolation structure than those on rigid foundation ; based on results of a series of shaking table model tests, prediction formulas for period elongation, damping ratio, SSI influence rate of interlayer displacement angle and SSI influence rate of isolation layer displacement of isolated structure model with small aspect ratios based on relative stiffness ratio of structure- soil body are preliminarily deduced ; the study results are helpful to promote wider application of structural isolation technology. © 2023 Chinese Vibration Engineering Society. All rights reserved.