SHAKING TABLE TEST OF NUCLEAR ISLAND STRUCTURE CONSIDERING SOIL-STRUCTURE INTERACTION

In order to investigate the impact of diverse foundation conditions on the seismic performance of the pile-soil-isolation bearing-nuclear island containment structure system, a simplified experimental model of the nuclear island containment-isolation bearing-pile-soil structure was devised in accordance with the equivalent stiffness principle. Comparative shaking table tests were conducted under the circumstances of medium-stiff soil, medium-soft soil and bedrock respectively, for both seismic and isolation working conditions. Based on these tests, a comparative analysis was carried out on the experimental phenomena, dynamic characteristics of the superstructure, acceleration responses and floor response spectra of the simplified test models under different foundation soil conditions in the seismic and isolation scenarios. The test results indicate that: taking soil-structure interaction into account, there are significant differences in the experimental phenomena and structural responses of the simplified test models under seismic and isolation conditions. The soil-structure interaction tends to reduce the natural vibration frequency of seismic structures, yet it has a relatively minor influence on that of isolation structures. When the site is not on bedrock, the isolation effect of the superstructure of the simplified test model is more pronounced, especially when the soil is medium-soft. For the same testcondition, the peak value of the floor acceleration response spectrum will increase with the increase of the input seismic motion amplitude, accompanied by a decrease in high-frequency components and an increase in low-frequency ones. The medium-stiff soil, medium-soft soil and bedrock foundation exert no influence on the floor response spectrum characteristics of the superstructure within the isolation system, but they do affect those of the superstructure in the seismic system. Specifically, the smaller the shear wave velocity of the soil, the larger the floor response spectrum response, which is predominantly concentrated in the low-frequency band.