| Earthquake disaster caused a large number of casualties and property losses.Therefore,it is important to improve seismic performance of engineering structures.At present,various damping control methods have been studied at home and abroad,among which have been used in actual engineerings.Recently,increasing research and development of controlling devices and smart materials open up a new area for structural vibration control.Shape Memory Alloys(SMA)are a class of novel smart materials that possess unique properties,including shape memory effect and superelasticity effect,which make them widely used in structural vibration control.Therefore,this thesis carried out the structural vibration control researches based on SMA damper.The experimental study of SMA material mechanics model was carried out in this thesis.The mechanical properties of two Ni-Ti SMA wires with different diameters were studied in this thesis.The effects of different loading conditions,cyclic loading-unloading number and strain amplitude on the mechanical behavior,such as energy dissipation per cycle,secant stiffness,equivalent damping and residual strain were analyzed,which provide experimental basis for research of damper.A class of new SMA damper(NSMAD)was presented in this thesis.Based on the constitutive model of SMA material,the mechanical model of NSMAD is established.Based on the experimental results,the mechanical models of wire group and helical springs of SMA in different loading and unloading stages are established respectively,and the NSMAD restoring force is solved by Newton iteration method.In addition,the parameters of NSMAD are studied in detail.The dynamic analytical method of frame structure incorporated with NSMAD is developed in this thesis.Firstly,the equation of the motion of structure incorporated with dampers is developed and the method of establishing the position matrix of control force is studied.Then,the relationship between equivalent horizontal force and control force of the damper based on the displacement equivalence principle is established.Finally,a 5-story Benchmark building is taken as an example to investigate the structure vibration control effect of SMA dampers under seismic excitations.At the same time,by comparing the damping performance of the novel recentering SMA dampers(NSMAD)with the ordinary spring recentering SMA dampers(OSMAD)can conclude that the NSMAD has a better control performance.The influences of parameters of the SMA’s area ratio,service temperature,bar diameter of the helical springs,coil diameter of the helical springs,effective number of coils of the helical springs on the damping evaluation indicators are studied.The influence law of parameters of NSMAD on the seismic evaluation indicators are mastered.An objective function of location optimization of dampers considering the requirements of safety and comfort of structure is established.Taking an international common model of 20-story Benchmark structure as an example,in order to use a suboptimal algorithm to place the dampers on various floors,considering the combination of two weighting coefficients of the objective function and four seismic excitations,the optimized positions and numbers of dampers are studied.Based on optimization results,the dynamic response and the objective criterion of the 20-strory Benchmark structure are analyzed.In addition,the control performance of NSMAD and OSMAD are compared,and the control performance of the proposed damper is further investigated.The vulnerability of Benchmark structure under earthquake action is analyzed,and the damage status of the structure in different earthquake intensities is evaluated. |
