Aseismic Analysis Of Frame Core Tube Structure With Retracted Facade By Conversion

Facade setback is a common building form in high-rise structures.The mechanical characteristics,design and construction of such structures are relatively complex.In order to study the influence of facade retraction on the seismic response and seismic performance of super high-rise structures,this thesis selects a super high-rise frame core tube project with conversion retraction on the top,and on this basis,adjusts the plane retraction scale,the height of retraction floors,and the conversion mode,and finally forms seven scheme models,which form a multi-directional comparison between each model.In the software SATWE,the vibration mode decomposition response spectrum method is used for small earthquake elastic calculation and analysis of seven models,to study the differences between the vibration characteristics,deformation sideshift and internal force distribution of each model,and to supplement the elastic time history analysis.The software SAUSAGE is used for elastic-plastic analysis.By comparing the internal force deformation,plastic development and member performance of each group of models in the major earthquake,the following conclusions are finally drawn:1.Through the small earthquake elastic analysis of each group of models by response spectrum method,it can be seen that the facade retraction can reduce the periodic value of the main vibration mode of the structure,and also has an impact on the higher-order vibration mode.The shear force and displacement of the upper floors are greatly reduced,and their amplitude increases with the increase of the plane setback scale and the number of setback stories.There are abrupt changes in the internal force distribution and displacement curve of the floor at the setback.The shear weight ratio of the upper floors has a tendency to enlarge,and there is a certain whiplash effect.2.In the analysis of the time history results and the comparison with the results of the same response spectrum,it is found that although the top facade retraction reduces the seismic action of the upper structure,the natural vibration frequency increases,making the shear force between the middle and lower floors of the structure increase rather than decrease.This is also reflected in the floor seismic shear amplification factor of each group of models.At the same time,the sudden change of floor shear force and inter story displacement near the strengthened floor and transfer floor is more obvious than that of response spectrum analysis.3.Through the large earthquake elastic-plastic time history analysis of each group of models,it is found that in the analysis model of each facade setback scheme,the damage of the transition setback and the bottom reinforcement area is obviously different from that of the vertical continuous structure.The shear wall of the floor near the facade retraction is destroyed first.The damage of the column end of the lifting column and the transfer inclined column is large and concentrated,but the damage of the bottom frame column is reduced.The above phenomenon is more obvious with the increase of the facade retraction degree.4.The same analysis method is used to study the performance difference between the steel reinforced concrete inclined column transfer scheme and the steel truss transfer scheme in various analyses.Through comparison,it is shown that the truss transfer floor has a significant effect in controlling the overall lateral displacement of the structure and mitigating the whipping effect of the superstructure,but the greater stiffness of the transfer floor leads to the greater ratio of the storey displacement angle with the upper receiving floor,so strengthening measures should be taken.