Rationality of Restriction of Minimum Proportion of Shear Force Born by Frame in Frame-tube Structure

Abstract:

It is specified that the maximum shear force born by the frame calculated according to the stiffness in the frame-tube structure should not be less than 10% of the total base shear in the Chinese national specification technical points of the special review for seismic design of super high rise buildings. However, due to some reasons, such as the building layout, this requirement sometimes is difficult to meet in engineering practice. This requirement is controversial. In order to investigate its rationality, five RC frame-tube structures were designed, and main variables are the stiffness of the frame, the strength of the frame and the type of coupling beams. Then the elastic response spectrum analysis and the time-history analysis under small, medium and strong earthquakes were carried out to assess the seismic responses of each structure. It is found that when the maximum shear force born by the frame calculated according to the stiffness is less than 10% of the total base shear amplifying the stiffness of the frame is not economic but leads to worse seismic performance. Amplifying the strength of the frame can reduce the damage of frame beams and improve the seismic performance of structure, but it can not form effective "strong column-weak beam" mechanism. Adopting coupling beams with large width and replaceable coupling beams can both lead to the dual system of core tube. The enhancement of energy dissipation capacity of coupling beams can protect the shear wall and outer frame effectively, and significantly improve the seismic performance of the structure.