Experimental Study And Theoretical Analysis Of Displacement-amplification Torsional Damping Device

Frame structure is one of the commonly used structural forms,in which beam-column joints are the important part.In the past earthquake,it can be found that many beam-column joints are destroyed under the action of seismic horizontal forces.In order to strengthen beam-column joints and enhance the overall seismic capacity of frame structures,a displacement-amplified torsional damper（DATD）with independent intellectual property right is developed in this paper.In order to avoid or alleviate the failure mode of"weak joints"in the frame,the design,development and experimental study of DATD damper are performed.Firstly,the structural parameters affecting the energy dissipation performance of DATD are determined theoretically,then 18 groups of simulated components with different parameters are designed so as to process the simulation analysis of their finite element numerical value.The influence of construction parameters on energy dissipation performance of damper will be identified by comparing the hysteretic curve,skeleton curve,characteristic parameters and stress nephogram.Then according to the results,the author will identify the mechanical model.The results show that the simulated hysteresis curve of the DATD is plumper and symmetrical,the hysteresis loop covers a large area,featuring strong energy dissipation performance and uniform stress distribution.Besides,the maximum stresses are distributed near the contact surface between the lead core and the rubber layer while there is no obvious stress mutation in the rest of the damper.And the mechanical model of the damper can be described by bilinear model.Lead core diameter（Φ）and distance between the lead core and the axis（a）,rubber layer diameter（2r₂）,Rubber Layer Thickness（h_r）,elastic modulus of rubber（G）and loading strain amplitude（γ）all will influence its energy dissipation performance,yet lead core diameter（Φ）features more prominently.It is suggested to improve the energy dissipation performance of the damper by increasing the diameter of the lead core as far as possible.On the basis of finite element simulation analysis,factoring into consideration the size of general beam-column joints,the author designed and manufactured a DATD and conducted the performance test of this specimen under low-cycle repeated loading circumstance.The tests include the fatigue test and large deformation test.The author studied the influence of strain amplitude and loading frequency on the energy dissipation performance of the DATD,and compared the test results with simulated analysis results.Then the author found that the hysteresis curve obtained by the test is plumper,the energy dissipation performance is stronger,the area of the hysteresis loop is larger and does not vary with the increasing cycle times.When the MTS was pressed downward,the limit plate would hold against the straight rack teeth,resulting in the hysteretic curve taking a shape of small top and big bottom.However,due to the large gap between gears under fatigue condition,the hysteretic curve will slip obviously under large deformation condition.On the basis of numerical simulation and experimental study of displacement amplification torsion damper,in this chapter the author first describes the mechanical properties of lead and rubber materials in theory,then establishes a general restoring mechanics model according to the structural characteristics of the damper.Then the author studies the influence of relevant design parameters on the restoring mechanics model,out of which the author puts forward the formula accessible to damper design,and finally gives design method of damper for practical application.