Design Of New Type Three-dimensional Seismic Isolation Device And Application Study In Ancient Timber Structure

In the paper,the status of research in vertical earthquake action,three-dimensional isolation device and a component disc spring,which are commonly used for vertical isolation were summarized.A new type three-dimensional isolation device was proposed to realize the three direction seismic isolation of Xi’an bell tower’s ancient wood structure.The research work and conclusions are as follows:（1）Based on the characteristics of dish springs and wire ropes,a kind of backpressure disc spring damper device was proposed.The design ideas and principles are that,whenever the device is pulled or pressed.The inside dish spring group is always t being pressed.The initial stiffness of the back pressure disc spring damper can be changed by changing the length of the pre-pull wire ropes.The parameter calculation formula of the backpressure disc spring damper is deduced,and a disc spring group with the vertical bearing capacity of 498kN and the limit deformation amount of 44.8mm is designed.An example is given to verify the rationality of the device design processes.Combined with the vertical isolation principle and the double broken line restoring force model of the backpressure disc spring damper.The new type of three-dimensional isolation device was put forward.（2）The finite element model of dish spring group and upper and lower plate is established by ABAQUS software.Friction coefficientμ₁ between disc spring is 0.005,Friction coefficientμ₂ between the disc spring and the upper and lower plates is 0.3.The contact ways of top-top involution and bottom-bottom involution are bind and surface to surface frictional contact respectively,Reasonable simulation results can be obtained.（3）Flat load of the whole model which under linear and sin functions compared with the specifications,the error is only 0.59%and 1.82%.The rationality of the whole model was verified,Then,the dynamic analysis of whole model was carried out under different preload,loading frequency and loading amplitude.It is obtained that the equivalent stiffness decreases first and then increases with the increase of loading frequency.But with the increase of initial preload and loading amplitude,the equivalent stiffness decreases slightly.The equivalent damping ratio increases with the increase of loading frequency and loading amplitude.The effect of pre-compression amount on the equivalent damping ratio is not significant.（4）Experimental research on backpressure disc spring damper,The results of the simulation are in agreement with the experimental results.Therefore,the rationality of the finite element simulation and the device is verified by static load test.The maximum error is8.97%,and the minimum is only 1.77%.The rationality of change regulation of the equivalent stiffness and equivalent damping ratio among loading frequency,preload and loading amplitude through finite element simulation were verified by dynamic load test.（4）The finite element model of Xi’an bell tower wooden structure was established through SAP2000 software.The rationality of the model was verified by comparing the calculation results with already existing research results.The angle between the backpressure disc spring damper and the lower connecting plate is compared and analyzed.The optimal angle is 60^o.The 3-D seismic isolation parameters which obtained by experiment was used as the attributions of the seismic isolation unit.The isolation analysis of bell tower wood structure under 7 seismic waves is carried out.It can be concluded that,the interlayer shear force and the interlayer drift angle was decreased,the XY direction acceleration time history curves had little difference of 41 joint and 69 joint.However,it has been reduced at the peak values.The acceleration and displacement of Z direction had a large reduction.Besides,the vertical bearing capacity,wind resistance and overturn resistance of isolation layer can meet requirements.Therefore,the effectiveness of the new type of three-dimensional isolation device was proved.At the same time,it can provide reference and technical support for 3-D seismic isolation for ancient timber structures.