Theoretical And Experimental Studies On Vibration Control System With Negative Stiffness Device

Given its reliability,easy maintenance and independence of external energy and signal,passive control is given considerable attention by engineers and researchers among many structural control strategies.It is the most widely used control technique.Most current passive control methods will increase the structure stiffness,which leads to effective displacement control and poor acceleration control.Moreover,current passive control strategies also have some drawbacks,such as residual deformation,maintenance after earthquake,damper durability and additional loads to the structure.Negative stiffness device(NSD)can reduce structure stiffness so that will be effective on acceleration and shear control.The increased displacement caused by NSD could be moderated by a proper damper.Shape Memory Alloy(SMA)has many superior characteristics such as shape memory effect,pseudoelasticity and anti-corrosion,which make SMA an ideal material for high-performance damper.Taking advantage of both NSD and SMA damper,a negative control system is designed in this paper.Effectiveness of the system is studied in both building and bridge Benchmark problem.The main work of this paper includes the following aspects:(1)A novel rail-type negative stiffness device is developed.Its mechanical properties are studied by shaking table test.Hysteresis loops of NSD with different per-compressions are obtained by employ cyclic loading;frequency response of proposed NSD is studied by sweep frequency test.Design method of NSD is presented.Theoretical model of NSD is established and be used to simulate its hysteresis behavior.Simulation result is in good agreement with test result.(2)A novel multi-dimensional SMA damper is developed and tested on a universal testing machine.Hysteresis behavior of the damper with different initial strain is studied by employing different load frequencies and different amplitudes in 20 degrees Celsius.Torsion characteristics of the damper are also tested.Theoretical model of the proposed SMA damper is established and be used to simulate mechanical property under cyclic loading.Simulation results of different amplitudes are coincident with test results very well,which proves the effectiveness of the theoretical model.(3)Negative control system is designed for 2nd phase Benchmark highway bridge model by uniting the proposed NSD and SMA damper.Simulink program is developed to investigate the effectiveness of the proposed control system.Simulation results show that the negative control system and sample semi-active control have similar effect,so that the negative control system achieve semi-active control result in a passive way.(4)Negative control system is designed for smart isolated Benchmark building and its effectiveness is studied.Control effects of negative control system under seven earthquakes are investigated and compared with sample passive,sample semi-active and sample active control.The results show that negative control system is more effective than the others in the control of displacement,acceleration and base shear.