| Conventional earthquake-resisting structure mainly depends on the plastic failure of the major structure to dissipate seismic energy,but it can cause large residual deformation so that the structure cannot be reused as well as recovered after the earthquake.Although,the application of seismic energy dissipation method can protect the major structure in some ways,but these measures cannot deal with the large deformation of the structure.Recently,the increasing research and development of self-centering structure system open up a new area for seismic vibration control in civil engineering.Shape memory alloys(SMA)are a class of novel smart materials which possess unique properties,including shape memory effect,superelasticity,high damping capacity,high corrosion resistance as well as extraordinary fatigue resistance,which make them perfect candidates for seismic energy dissipation devices in structural engineering.Superelasticity of SMAs indicates that there is no residual deformation while they dissipate energy,which can be widely used in the area of vibration control in civil engineering.Numerous studies have been conducted to use the SMA materials in structural vibration control,and a great many of SMA dampers have been attained.However,the research of SMA dampers is still at the experimental stage,and there still exist some problems and the SMA dampers aren't yet applied in engineering structure by far.So the means of theory analysis,experiment study and numerical simulation are adopted to carry on the research of an innovative SMA damper.Main contents of this paper can be shown as follows.(1)The development of the structural vibration control technology and the application status of SMA in civil engineering are presented in detail.The microscopic mechanism of shape memory effect and superelasticity of SMA is described.Besides,several typical macroscopic phenomenological constitutive models of SMA are also presented in this thesis.(2)Tests and experiments on superelastic Ni-Ti SMA wires are conducted to explore the influences of cycles,strain amplitude,loading rate,environment temperature,pre-stressing degree and other factors to the hysteresis behavior and mechanical properties of the SMA,and the changing law of the mechanical properties of the SMA under the effect of these factors is obtained.Besides,the superelasticity of Ni-Ti SMA wire,which is tested in the experiment,is simulated by ANSYS software,and the simulated results are contrast with the test ones.(3)An innovative SMA self-centering energy dissipating brace is designed with superelastic Ni-Ti SMA wires,which provides some degree of energy dissipation capacity with negligible residual displacement.This new device also has such advantages as the fact that the SMA wires are always in tension,no matter the brace is subjected to tension or pressure.(4)Four sets of the innovative SMA self-centering energy dissipating brace are fabricated to carry out the research on the mechanical properties of the brace.The influences of the section area of the SMA wires,displacement amplitude,loading rate and prestress of the SMA wires to the hysteresis behavior and mechanical properties of the innovative SMA self-centering energy dissipating brace are considered.Besides,the innovative SMA self-centering energy dissipating brace is also simulated by ANSYS software.The comparison indicates that the simulated results are consistent with the test ones.(5)A 9-storey steel frame structure,installing with common braces,buckling-restrained braces and SMA self-centering energy dissipating braces respectively,is analyzed by elastoplastic seismic time-history analysis to contrast the influences of different types of braces to the anti-seismic properties of the 9-storey steel frame structure.The analysis results show that the SMA self-centering energy dissipating braces can reduce the structural responses induced by the earthquake,and the residual displacement of the structure after the earthquake can also be controlled effectively. |
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