Seismic Response Analysis Of Large-span Space Lattice Shells And Study On Vibration Control

Large-span space latticed shell structures are used more and more in people's lives for they are aesthetically appealing with layout flexibility and can satisfy the requirement of large space. However, long-span space structure is very sensitive to seismic response for they belong to the flexible structure, their vibration period is long and damping is small, they sometimes will lead to greater vibration and generate larger deformation, the structures with larger planar size are different from each fulcrum ground motion, the spatial changes of ground motion will have an important influence to seismic responses of structures, so, considering the multi-point ground motion input is very necessary.The seismic responses of large-span space latticed shell structures are calculated respectively in consensus input and multi-point input, the changing regularity of seismic responses was obtained. At the same time, with the special physical and mechanical performance, Magnetic Shape Memory Alloy (MSMA) is used to make two kinds of actuators independently, accordingly, the active control systems are exploited, two model structures is designed and made, the simulated seismic shaking table tests are carried on the two model structures. The main research works of the paper are as follows:(1) A single-layer reticulated spherical shell structure with planar diameter 80m is as an example, under vertical and horizontal consistent input; equations of motion and response spectrum are analyzed. The finite element analysis model of the single-layer reticulated spherical shell structure is established with ANSYS finite element analysis software, the rods internal force and nodal displacements of model structure under vertical and horizontal consistent input are studied by CQC of consistent input response spectrum, the major effect factors are discussed, the laws of consistent input seismic response are summarized.(2) Based on the analysis of the consensus input, equations of motion and response spectrum of multi-point input are studied, the acceleration response spectrum calculation formula is derived based on pseudo excitation method. The horizontal and the vertical seismic response of the model structure under multi-point input is conducted, at the same time, the analysis results of consistent input and multi-point input are compared, The contrastive analysis of horizontal and vertical multi-point input are conducted to reveal the changing rules of the rods internal force response and node displacement response. The influence of the traveling wave effects are discussed, it provides the reference for large-span space latticed shell structures design.(3) Using new materials preparation and experimental mechanics methods, Ni-Mn-Ga is selected as the main ingredients of MSMA material. After several times materials preparation and material performance tests, considering coupling of magnetic field, temperature and prestressing etc. factors, Ni-Mn-Ga chemical composition contents influence physical and mechanical properties of MSMA, and the influence law is analyzed. The good performance alloy materials of Ni₅₃Mn₂₅Ga₂₂ is prepared, the magnetics performance tests are done, and the magnetics constitutive models of Ni₅₃Mn₂₅Ga₂₂ alloys are established in different conditions of magnetic field, prestressing and deformation etc.(4) As the self-designed MSMA materials are core elements, the working principle and structural method of the MSMA actuators are systematically analyzed from magnetic field and magnetic circuit, prestressing device, temperature control device, etc. it put the emphasis on the magnetic circuit optimization and analysis. Through the reasonable idea and optimization design, two types of new MSMA actuators are independently researched and produced, and the corresponding field-actuator performance tests are done, the main influence factors and general rules are analyzed, the static/dynamic constitutive models of the MSMA actuators are established. The results show that the dynamic response frequency of the MSMA actuators can reach 200Hz above, and the output force is larger, it can satisfy active control needs of the earthquake response. (5) On the basis of two types of new MSMA actuators researched and developmented independently, the compositions of the active control system, control principles and realization methods are studied, the reasonable control strategy is designed, the control algorithm is planed and optimized, then, the corresponding controller is made,the two kinds of MSMA active control system is integrated and exploited, and the corresponding control performance tests are done. The results show that the MSMA actuators and active control system developed in this paper have better adaptabilities, they can actively control seismic response of shell structure.(6) Using different slenderness ratios of the rods, two experiment models of Kiah witter space reticulated shell structure are designed and made, the MSMA actuators position and number are optimized by genetic algorithm, the earthquake simulating shaking table tests of the experiment models with the MSMA active control systems and no MSMA active control systems are done, in the tests, the sine waves, EL-centro seismic waves and Taft seismic waves are respectively input, more than 20 kinds of experimental conditions are completed. The results indicate that the two MSMA actuators and active control systems can well control seismic responses of the model structures, usually the control effects can reach 30%, it is shows that the MSMA active control systems are feasible and efficient, they have good researching value and application prospect.