Study On Mechanical Properties And Seismic Performance Of Metal Torsion Damper With Displacement Amplification

Shear types and tension-compression types metallic dampers rely on the plastic deformation of metallic materials to dissipate energy,while the energy dissipating capacityis not performed sufficiently due to the local deformation.Compared with them,pure torsional dampers have the lager plastic deformations to dissipating energy and display the same mechanical properties in all cross sections.However,the superior plastic deformation is not extensively utilized.To this end,a displacement-amplifying pure torsional metallic damper,which can convert and amplify the linear motion into rotational motion on the basis of a ball screw,is proposed to greatly improve the energy dissipation capability.In the present study,the work principle,the mechanical model,and the vibration control performance of the displacement-amplifying pure torsional metallic damper are in-depth investigated.And the main contents are drawn as follow:(1)In order to state the purpose of the dissertation,a comprehensive state-of-the-art review of the metallic dampers and displacement-amplifying pure torsional metallic dampers is provided for structural vibration induced by external dynamic loads.Especially,the vibration of the long-span bridges and high-rise buildings under wind,earthquake loads are introduced elaborated.(2)A single-degree-of-freedom model equipped with steel damper is established to obtain the coupled equation of motion.And the damping force is expressed in the form of segment.Based on the model,the analytic recurrence relationship between motion amplitude and period are derived,and the expressions of analytic recurrence relationship and the structural attenuation curve due to free vibration are obtained.Moreover,the damping characteristics of the steel damper under free vibration is further illustrated.(3)Tensile and torsional tests were carried out on aluminum 1060 so as to analyze the failure modes and plastic deformation capacity under tensile and torsional.What’s more,the torsion test was performed on aluminum 6061 solid round rod,hollow round rod and anti-yielding hollow round rod whose mechanical properties were studied.(4)A displacement-amplifying pure torsional metallic damper was proposed and manufactured,and the constitutive relation was deduced.Also,the impact of damper parameters on elastic stiffness,plastic stiffness,yield displacement and yield force was discussed by theoretical study.To compare with the theoretical model,a pseudo-static test is carried out.(5)A finite element model of a semi-floating cable-stayed bridge with displacement-amplifying pure torsional metallic damper was established to investigate the seismic performance under different earthquake ground motions.Furthermore,the impact of the lead of the ball screw,the outer diameter and the length of the metal rod of displacement-amplifying pure torsional metallic damper on seismic behavior of the cable-stayed bridge is discussed.