| As a kind of active and effective countermeasure for seismic protection, the vibration control in civil engineering has be studied over the past40years. In recent years, the application of intelligent material (such as MR、PZT and SMA) and smart structure are becoming one of the hotspots in the research field of civil engineering control. At present, MR damper has been more mature, so it is necessary to strengthen research and development of the other semi-active control devices. This dissertation puts forward three new types of piezoelectric friction dampers, and by making full use of the quick action of PZT and the direct and converse piezoelectric effect, they improve the performance of existing piezoelectric damper, to promote the practical process of the piezoelectric dampers.Piezoelectric actuator possess the converse effect. Namely, it can generate adjustable force by controlling the applied voltage, and it is characterized by simple and reliable control system which provide a convenient for its practical application. In this dissertation, commercially available multilayer piezoelectric stack actuators are considered for driving variable friction damper, and by using SMA wires and friction damper, a PZT and SMA compound friction dampers is proposed innovatively. It is considered that the applications of independently developed PZT-SMA combined dampers in the semi-active and passive control. The theoretical analysis and experiment of structural control system were performed, Theoretical conception is proposed on the self-powered PF damper. The primary contents include as follows:(1) Two kinds of new type piezoelectric friction dampers with and without SMA are proposed, and the scale dampers are designed and fabricated. Firstly, the force generation of the piezoelectric actuator is tested and shows the force increases as the voltage. Secondly, the performance experiment is carried out under varying voltage to identify its motion-independent characteristics on two-way slide. Experimental results indicate that the load-displacement curves are stable and independent of the excitation in low frequency range (0.01-0.06Hz). On two-way slide, the larger difference in the initial stiffness of the x, y direction is existing at the sliding phase, but after sliding stability, two-way dynamic characteristics is stable.(2) Because of the complex structures of the new damper, it is no longer applicable for piezoelectric adjustable pressure formula currently based on one-way Hook theorem. Therefore, the finite element analysis program ANSYS is put to use and deformation test is done to prove correctness of calculation. The shape factor of piezoelectric damper is decided based on the analysis. it also demonstrates that piezoelectric normal pressure eccentric has little effect to the adjustable damping force, and the eccentric impact formula is derived. At the same times, the optimization on the parameters of smart damper stiffness is done by using the finite element analysis.(3) The simulation analysis for the intelligent high inter-story seismic system has been done. The proposed control strategy was applied to a14-story isolation structure which is an actual project to simulate its seismic effectiveness under five ground motion records, The control evaluating index are decided, moreover the control algorithms of there composite friction dampers are further investigated, and the Optimal-Voltage Control and Clipped-Optimal Control are the proposed two kinds of methods of control strategies. Numerical simulation shows the two kinds of methods are all effective for suppressing the seismic responses. The implementation of optimal-voltage control needs only power-supply, so the control cost decrease and the reliability increase. And the application value is clear.(4) Experimental validation is also carried out by using a series of shake table tests on a4-story steel isolated structure model (including base-isolation and first-story isolation) controlled with the smart dampers with SMA and without SMA. The performance of the compound smart friction damper and the control strategy are evaluated experimentally. Before the tests, numerical modeling and simulation were conducted. The analysis results were contrasted with the test results under different earthquake waves. The comparison indicate that the simulation is correct and the damper is effective in mitigating earthquake responses on both passive control (optimal-voltage control) and the semi-active control. The optimal-voltage control can achieve better performance. the effectiveness of the control strategy was verified with shake table tests conducted on a1/4scale,4-story isolation. In order to simplify the installation, the piezoelectric friction dampers are located at the centre of the isolation structure.(5) When accidental eccentricity leads to the seismic torsional effects, the smart damper can provide anti-torsional tension and damping by using SMA wire. Both the numerical simulation and shake table tests have all proved that the accidental eccentricity does not lead to the larger torsional vibration. And the current smart dampers are required to be arranged in the structure around the plane to anti-torsion. (6)A self-powered piezoelectric damper is proposed, through it the smart inter-story isolation system is established theoretically. It makes full use of the quick action of PZT and the direct and converse piezoelectric effect, so the smart isolation can get rid of the external power supply. Seismic waves is the power generation excitation, then piezoelectric power generation is designed and the formula for calculating the piezoelectric power generation is derived. Numerical simulations for inter-story isolation equipped with this system excited by historical earthquakes are conducted and shows it can suppress the seismic responses. |
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