Study On Seismic Torsion Response Of Complex Eccentric Structure

Recently,as the economic development,a large number of unique shape irregularities come to our normal life.Because the layout of the structure is irregular,its rigidity center could not match the mass center.In the process of holding the seismic loading,the torque is generated in the structure horizontally,and then the torsion phenomenon occurs.Torsion is one of the main factors that cause earthquake damage,so it is very necessary to study the influence of it.There are many researches on the dynamic response law of the single layer and the uniform eccentric structure,but the result of the dynamic response law of the torsion effect of the complex eccentric structure is less.Under this background,the main research contents and results are as follows:(1)In order to reduce the influence of the proportional factor in the test model,the maximum size of the shaking table in China was selected for a large proportion of similar model tests under earthquake simulation,with 1:20 ratio compared to the real complex eccentric structure.The response data were analyzed.Results showed that,with some components in the plastic stage,the torsional response frequency band gradually away from the translational response frequency band,torsional coupling degree decreased.The distribution trends of the torsional effect of different earthquake loads caused by different seismic loads were basically the same in the stage of small earthquake and middle earthquake.In the stage of large earthquake,the torsional effect of the model changed in the distribution of each layer.(2)According to similarity ratio,the results obtained from model tests were used to get corresponding results in the original structure.Then,the interaction calculation model was established.According to the analysis of numerical simulation,the differences between the dynamic response of the rigid foundation structure and the interacted complex eccentric structure were compared.Considering the influence of the soil,the displacement response of the superstructure,the base shear force and the internal force of the structure were reduced.The reduction of the torsional displacement was the largest.(3)Based on the Sheng-Jin formula,we proposed the explicit analytical solutions of the frequency and vibration mode of the single-layer bidirectional eccentric structure.In this paper,we obtained some results.Specific rules are as following: with the increase of the eccentric angle,the torsional effect of the structure becomes stronger;different single-layer bidirectional eccentric structures correspond to a particular eccentric angle to maximize its torsional degree;the coupling effect of the structure becomes the strongest when the main frequency ratio of the torsion and translation is close to 1,while the effect of the secondary frequency ratio of the torsion and translation is weaker.(4)In order to manipulate the changes of the parameter,the complex eccentric structure was shown as a simplified model.Accordingly,the structural parameters of the simplified model were adjusted.The effects of different eccentric distances and angles on the dynamic response of the complex eccentric structure under different earthquake excitations were discussed.The analysis showed that when the eccentric distance changed,the analysis of each layer of the structure under earthquake excitation is consistent with that of the single-layer bidirectional eccentric structure.But the magnitude of the torsional response of the structure was not consistent with the length of the eccentric distance of each layer.When the eccentric angle changed,the law of the torsion effect was first decreased and then increased.Furthermore,the influence of eccentric angle variation on complex eccentric structure under bi-directional earthquake excitations,was not as significant as that under one-way load.