Research On The Design And Caculation Of Reaction-Mass-Foundation Of Triple Shaking Tables Of Earthquake Simulation

Shaking table of earthquake simulation is the most effective equipments on testing the seismic performance of buildings or structures. It can be seen as a large source while the shaking table is on operation, which needs a huge reaction-mass-foundation to decrease the vibration. Reaction-mass-foundation is a very important component in the shaking table, but it is not a rigid body of infinite weight yet. The research of single shaking table system indicates that the reaction-mass-foundation does produce somewhat vibration and will be inevitably occured resonance with the shaking table. Therefore, the vibration of the reaction-mass-foundation must be definitely evaluated to control the damage and ensure the safety to the surrounding structures before the shaking table was built. Shaking table array system made up of small and mediumsize tables is the current of future development. At present, the research on dynamic characteristics of reaction-mass-foundation of shaking table array system has not yet published by literatures. Therefore, this paper mainly carries out the dynamic characteristics of reaction-mass-foundation of the portable earthquake simulation shaking table system.The main work and conclusions in this paper are presented as following:(1) The methods of design and calculation of the reaction-mass-foundation beneath the earthquake simulation multiple shaking tables of Fuzhou University were studied, and the key techniques of design and construction of the reaction-mass-foundation are presented detailedly, such as the installations of high precision embedded parts, the pouring method of large mass concrete and the maintenance of later concrete solidification period. The studies can provide some references to other department for building the reaction-mass-foundation of shaking table array system.(2) The dynamic characteristics test and seismic response of the reaction-mass-foundation were carried out by the excitation of sine sweeping waves and earthquake waves with a single large shaking table and synchronous three tables. The influences on the structure and the surrounding environment during the operation of shaking tables array were analyszed. The results show that the vibrations of reaction-mass-foundation are less than 0.1g that completely satisfies the requirements of the relevant literature, and the influences to the surrounding buildings are closed to 0.01 g that fulfill with the provisions of specifications. Therefore, the design and construction of reaction-mass-foundation is reasonable.(3) The finite element model of the reaction-mass-foundation of the earthquake simulation multiple shaking tables is established by ANSYS software. The reaction-mass-foundation vibration characteristic parameters were analyzed used the finite element model which was verified. The analytic results release that when the three tables at a closest location will have the largest influence on the vibration of the foundation, and the setup of vibration isolation trench using isolation rubber can obviously weaken the vibration effect. The calculation results also show that the varying of the weight and stiffness of the reaction-mass-foundation have greate impact on the initial order modal of foundation.(4) The lumped parameter method for designing and calculating the reaction-mass-foundation of earthquake simulation multiple shaking tables is introduced. The analysis using the calculating model and dynamic equation of Mass-Spring-Damper that is referred to the Specification for Dynamic Foundation Design is established, and which is also compared with Lysmer matching method and the Foundattion Engineering Handbook. The results show that the method of Specification for Dynamic Foundation Design can agree with the test result best, which can be used to design and calculation of reaction foundation beneath multiple shaking tables.