Research On The Seismic Performance Of Spring Vibration Isolation Foundation Of Steam-turbine Generator Considering Gravity Effect

The problem of gravity similar of the scale model test is one of the difficulties in structural tests. It is difficult to satisfy with the gravity similarity conditions between prototype and model with additional weight. The physical and mechanical properties of the prototype and model materials are not completely similar if change model material to satisfy with the gravity similarity conditions.This article attempts to do not change the material of the structure, The prototype and the model can satisfy with the gravity similarity condition between the prototype and scale model through the method of applying vertical force. This paper based on a spring vibration isolation steam-turbine generator foundation, a 1:8 foundation model is designed and fabricated. The free vibration characteristics were tested by the method of three-point space excitation, the natural frequencies, mode shapes and damping ratios of each order were obtained, the distribution of natural frequencies is also studied. Research shows that the first mode of the foundation is transverse horizontal translation, the frequency distribution below 10Hz is dense, which is far away from the working frequency of the steam-turbine generator, the basic cycle is much larger than the value of the characteristic period.During the earthquake resistant test, vertical force was applied to the model to simulate gravity by Hydraulic Loading System. Eliminate the horizontal component of the vertical force generated by the deformation of structure in the program design.Earthquake resistant tests were performed under seven different test conditions in all. Three different test conditions of 7th intensity medium earthquake of pseudo dynamic test were performed under transverse load, three different test conditions of 7th intensity medium earthquake and a 8th intensity rare earthquake of pseudo dynamic test were performed under longitudinal load.During the pseudo dynamic tests, the foundation roof time-histories response of displacement, velocity, acceleration and restoring force were got and the hysteresis curves were produced of different test conditions; the time-histories responses of the top of columns, the beam column joints, the intermediate plates and the baseplate were got; the inter-story drift angles were calculated to determine whether the values of the inter-story drift angle is satisfied with the requirements of Code for Seismic Design of Building (GB50011-2010); the deformation of springs is studied through data, spring vibration isolation system made a more rational distribution of the earthquake action to each column; got the steel bar strain time- history of vertical (horizontal) roof beam, top of columns, beam column joints and root of the columns to find the parts of complex-loaded and high stressed. During the pseudo dynamic test of 8th intensity rare earthquake, the development and distribution of cracks are observed in detail; investigated the anti-glide ability of Non-slip mats which located up and down the spring vibration isolator.