Diagrid Core-tube Structure Seismic Performance Based on Equivalent Stiffness Ratio of Inner and Outer Tubes

To study the relationship between the stiffness ratio of the inner and outer tube of the diagrid core-tube structure of high-rise buildings and the redistribution of the storey shear force, the structural ductility, overstrength factor and the seismic performance, a total of 12 kinds of diagrid core-tube structures of equivalent stiffness ratios were established at 71°, 77° and 80° diagonal angles. Based on the static pushover analysis method, combined with the principle of capacity spectrum and demand spectrum, the characteristics and laws of the position change of the weak layer, the redistribution of the storey shear force, the shear lag effect of the bottom compression flange and the overall ductility of the structure are analyzed under the action of the frequent earthquake (70 gal), fortification earthquake (200 gal), rare earthquake (400 gal), extremely rare earthquake (510 gal) and huge earthquake (620 gal). The results show that under different earthquake actions, there is an obvious redistribution of floor shear force in the diagrid core-tube structure, and the storey shear coefficient decreases with the increase of earthquake level and equivalent stiffness ratio. The diagonal angle is the main factor affecting the location of the weak floor and the shear lag effect. The shear lag effect of the structure increases with the increase of the seismic fortification level. The structural ductility with a diagonal angle of 77° is generally optimal. When the equivalent stiffness ratio is 0.64, the structural ductility reaches the optimal value of 1.46, which is 1.1 times that of 71° and 80° diagonal angles. In the structure with the same diagonal angle, the overstrength factor increases with the increase of the equivalent stiffness ratio.