Development Of Self-Centering-Energy-Dissipation Device Based On Shape Memory Alloys And Application Research On Seismic Performance Of Steel Frame-bracing Structures

Earthquake is one of the most serious natural desasters with characteristics of unpredictable,enormous damage,accompanying fires,explosions,and tusnamis,and so on.The traditional structures usually resist earthquake and dissipate seismic energy mainly based on the strength,stiffness and ductility of themselves,which usually leads to yielding or damage of structure components.Structures with energy dissipation components dissipate energy relying on the damping components in which large residual deformation leaves after strong earthquakes.These two types of structures with or without dissipation components require huge repaire costs or could hardly repaire.Research on structures with the functions of energy dissipation and self-centering has become research focus in the seismic resistance of civil engineering.Meanwhile,the traditional onefold two-stage seismic design theory,which only emphasizes the design target on human safety,exposed many shortcomings and should be improved.Consequently,performance-based design for seismic resistence also becomes one of the hottest topics of the reseatchers around the world.For these reasons,by means of theoretical analysis,experimentation and numerical simulation,this paper firstly studies the mechanical properties of the shape memory alloy(SMA)material,and revises the multi-linear constitutive model.Then the seismic performance of an SMA based self-centering-energy-dissipation device(SCED),and the performance of pin-connected steel frame structure installed selfcentering-energy-dissipation devices(SF-CEB)are researched.Based on the thought of performance-based seismic resistance,performance-based design is applied to a steel framebracing structure(SF-CB)with 12 floors.The main contents of this paper are as follows:(1)The research and application of structural vibration control technology are introduced in detail,and the latest research results of the SMA based self-centering-energy-dissipation devices are summarized,then the main contents of this thesis are put forward.(2)The constitutive models of SMA are summarized as the T-L-B sequence,O-G-W sequence and others.The multi-linear model used in this paper is introduced in detail.The phase transformation temperatures of superelastic Ni-Ti SMA wire are tested using differential scanning calorimetry(DSC).The mechanical property of SMA wire is also tested.The influences of cyclic number,diameter of wires,loading rate,loading amplitude and prestrain on the mechanical property of SMA wire are investigated.The expression considering multifactors of the mechanical property of SMA and the modification function of the constitutive model are proposed.The multi-linear constitutive model of SMA is revised.(3)A new type of self-centering-energy-dissipation device based on SMA is developed.The mechanical property experiments of the device are conducted.The influence of the core area of SMA wires,loading rate,loading amplitude and initial stress of SMA on the mechanical behavior of the device is discussed.Moreover,the expression function considering multi factors about mechanical property of the device is proposed.The finite element model of the device is established.The performance of the devices is numerically simulated and compared with the experimental results.It is found that,the simulation results of the SMA based self-centeringenergy-dissipation device are in great consistency with the experimental results.The three-stage theoretical model of the self-centering-energy-dissipation device is also put forward.(4)A 1:2 scaled two-story single-span planar pin-connected steel frame-self-centeringenergy-dissipation bracing structures(SF-CEB)is designed and produced.The experimental results show that the SF-CEB structure has good energy dissipation capability and can recentering to its initial state after unloading.The validity of the self-centering-energy-dissipation device is verified.The structure has stronger lateral resistance,greater ductility and re-centering ability.(5)The equivalent expression of the parameters of self-centering-energy-dissipation brace is proposed.The equivalent beam element model of the SF-CEB structure is established for numerical simulation.It is found that the numerical simulation results of the model can match the experimental results well.The simulation of the SF-CEB structure based on the established model provides research basis for the performance-based analysis.(6)The performance level of the SF-CEB structure is refined,and the performance level evaluation indexes based on maximum and residual inter-story displacement angles are proposed.The procedure of the performance-based seismic design for SF-CEB structure is established.Performance evaluation of an existing steel frame-bracing structure(SF-CB)with 12 floors is carried out.The shock absorption rate and the recentering rate requirements of the structure are put forward.The performance-based design of the SF-CEB structure is carried out by using dynamic time history analysis method.The performance of shock absorption and selfcentering of the SF-CEB are discussed.The analysis of this type of structure provides references for the development and performance-based design of self-centering structures.