Study On A New Type Of SMA-Rubber Bearing Performance And The Application In Frame Structure

In this paper,a new type of SMA-laminated rubber isolation bearing is designed based on the superelasticity and high damping characteristics of shape memory alloy(SMA)to overcome the shortcomings of ordinary rubber bearings,such as small initial horizontal stiffness,poor energy dissipation capacity and large horizontal displacement under earthquake.And the mechanical properties of the bearing and the isolation effect applied in frame structures are studied.The main contents of this dissertation are as follows:In order to obtain stable isolation effect in all directions of horizontal and vertical force,and to bearing the bearing arises a larger moving distance,the bearing adopts the combination of SMA wires take shape with right triangle to form a hexagonal system.Two different bearing schemes are designed according to the different combination modes of SMA wires.Through analysing the motion state of the bearing in different directions and the formula derivation,the relationship between the horizontal restoring force and the vertical pulling force along two orthogonal directions and the movement distance is obtained.And the formula for calculating the ultimate displacement of the bearing in the superelastic range of SMA is determined.The study above provides a theoretical basis for the subsequent analysis and comparison of the bearing forces.In order to analyze the mechanical properties of the bearing,the SMA constitutive relationship is programmed by using MATLAB software.The constitutive model is fitted by comparing the experimental data to determine the reasonable model parameters.By using the established constitutive relation,the simulation fitting program is compiled for calculating the horizontal restoring force and the vertical pulling force of the two bearing schemes and the ultimate displacement in the SMA superelastic range.What is incestigated are the influence of horizontal distance and net height of SMA wire system,cross-sectional area of SMA wire,pre-strain and pre-stress of SMA on the bearing.In addition,the change of the bearing performance under different displacements are also analysed.The variation rule of the performance index is summarized to provide theoretical guidance for the performance adjustment in practical application.In order to understand the isolation effect of SMA-laminated rubber isolation bearings,the SMA-laminated rubber isolation bearings is apply to a single-degree-of-freedom isolation system based on the calculation results of the restoring force of the bearings calculated by MATLAB program.What is analysed was the response of the system under the excitation of simple harmonic waves with different circular frequencies.The results show that the isolation effect of SMA-laminated rubber bearings is more remarkable.In addition,SMA-laminted rubber bearings can reduce the relative displacement distance of rubber bearings in single-degree-of-freedom isolation system,which makes up for the shortcoming of small stiffness and large displacement of rubber bearings under seismic wave action.Using ABAQUS software,the finite element model of 7-storey frame structure is established,and what is obtaind are the natural vibration characteristics of the frame structure under three different bearing conditions.The results show that both SMA-laminated rubber isolation bearing and rubber bearing can prolong the natural vibration period of the structure.The results of seismic response analysis of frame structures with three kinds of bearings show that the new SMA-rubber bearings can effectively control the displacement of the bearings,which decreases by 11.5% compared with the rubber bearings,and the new SMA-rubber bearings have more obvious effect on reducing the acceleration and displacement of each layer in the structure than the ordinary rubber bearings,both of which are about 20% lower than the latter.In order to further understand the isolation effect of SMA-laminated rubber isolation bearings under different seismic action,the frame structures with three kinds of bearing is analyzed by frequency modulation,amplitude modulation and different seismic waves to obtain the seismic response.The results show that the isolating effect of SMA-laminated rubber isolation bearings is better than that of ordinary rubber bearings when the seismic wave amplitude is larger.SMA-laminated rubber isolation bearings perform a better isolation effect on hard ground,and may magnify the seismic effect on soft ground.The isolation effect of SMA-laminated rubber isolation bearings under three different seismic waves is better than that of ordinary rubber bearings.The vibration frequency of seismic wave is higher when the interval time is shorter.And under seismic waves with shorter interval time,the isolation effect of SMA-laminated rubber bearing is better.