Research On Key Issues In Design Of Large Earthquake Simulation Shaking Table Foundation

Earthquake, which may endanger personal safety, result in property damage, environmental pollution and so on, is a kind of major natural disasters. It can cause serious damages, especially on buildings, bridges and other infrastructures. In recent years, most areas of our country are in the earthquake prone period. Therefore, the risk caused by the earthquake is also increasing, and how to reduce the casualties and economic losses caused by the structural damages in the earthquake has become a problem to be solved. The earthquake simulation shaking table is the most effective and direct tool for seismic performance testing of engineering structure or mechanical and electrical equipment. The earthquake simulation shaking table, which is the most direct method to study the seismic response and failure mechanism in the laboratory, can simulate earthquake process and artificial seismic wave test fully. This equipment can also be used to study the dynamic characteristics of structures, the seismic performance of equipments, and test the seismic behavior of structures, so it is of great practical significance for the research on the design and construction of the earthquake simulation shaking table. The foundation of the earthquake simulation shaking table supports the whole shaking table system. If the vibration of the foundation is too large, it will not only undermine the movement performance of the surface, but also affect the health of working staff on site. What more serious is that it will harm the surrounding buildings and facilities. Consequently, the foundation must be designed reasonably in the construction of the shaking table, and the maximum vibration of the foundation must be controlled within the specified range.The main contents of this paper include:(1) The method for determining load and parameters of foundation soil, and allowable standard of the foundation vibration are described in detail. Based on the design of the equipment information, site information, seismic effect and the corrosion of the site soil and other design backgrounds, scheme comparison of preliminary design is carried out according to the relevant design criteria. In view of the detailed design according to comparison results and the specification, the design parameters of the two different design schemes are obtained.(2) According to the principle of the lumped parameter method, two design schemes are checked by the ideal lumped parameter method. Then the vibrations of the shaking table foundation under different kinds of disturbing force are analyzed to get the amplitude and frequency of different kinds of vibrations (vertical vibration, torsional vibration, horizontal tilt coupling vibration, eccentric vertical vibration). The optimal scheme is selected by comparing the amplitudes of the two different design schemes. Through the calculation, it is concluded that for the first scheme, the horizontal amplitude of the foundation is 0.077mm, and the vertical amplitude is 0.150mm, which both meet the requirement of the specification limits.(3) Using the three-dimensional entity structures of Solid45 element concrete foundation, and the contact relationship between the ground and foundation simulated by the spring-damper elements COMBIN14, it is concluded that the displacements in three directions of the shaking table foundation in the process of the shaking table opening by means of finite element simulation. Compared with the results obtained by the lumped parameter method in the third chapter, it follows that the displacement value of the foundation under vibration can meet the requirements of the standard, and the lumped parameter method can be used as a design method.(4) The following conclusions can be obtained by parametric analysis of foundation stiffness, foundation quality and foundation damping:1) The change of foundation stiffness has no significant effect on the vibration of the shaking table foundation;2) When changing the foundation quality, as the foundation quality becomes larger, the mass ratio of the foundation becomes larger, the foundation damping becomes smaller, and the vibration effect becomes larger. Therefore, in the process of building and designing the concrete foundation, the low-density concrete should be selected to help reduce the vibration response;3) When changing the foundation damping, as the foundation damping becomes larger, the vibration effect of foundation becomes smaller, which shows that the increasing foundation damping weakens the resonance effect of the foundation.(5) The original design scheme of the new laboratory Hall of Jiulong Lake Campus of Southeast University is in accordance with the condition of 7 degree seismic fortifications. The dynamic action during the opening process of the shaking table should be considered in accordance with the service load into the load combinations. On the basis of considering the dynamic effect of the shaking table, the original design scheme is optimized, and the three point optimization measures are put forward:1) Increase the lateral stiffness of the vertical component of the main structure;2) Increase the horizontal stiffness of the floor system of the main structure;3) the original PTFE rubber pad between the capital and the roof is modified to set up the rubber vibration isolation bearing.(6) Considering the influence on the surrounding environments during the opening process of the shaking table, the vibration effect in the range of 15m around the shaking table foundation is calculated according to the relevant guidelines Code of for Dynamic Machine Foundation Design. The vibration effect 15 meters away from the shaking table is 0.009g, which meets the requirements of the specification.