Optimization Design Of Frame-Core Tube Structure Based On Seismic Performance

Frame-core tube structures are widely used in high-rise buildings. Cores are the major lateral force-resisting components in frame-core tube structures. Seismic performance of the frame-core tube structures depands on the cores.Currently, the research on cores cannot fully meet the need of the constructions. In this paper, theoretical analysis and finite element analysis were further conducted to analyze the deformability, failure modes, ductility and energy-dissipation of the cores under seismic loads. The main contents are summarized as follows:The thickness of the cores is expressed respectively as linear, quadratic and cubic formula relating to its height. The peak displacement and the maximum interstory drift are calculated under the lateral loads. Results show that the cores have smallest deformation when using quadratic and cubic formula to express the relationship between core’s thickness and its height. The thickness and height of core with a quadratic equivalent formula relation is recommended when designing the cores.By comparing different failure modes of the cores, the assumption that the ideal failure mode is the flexural failure at the bottom section prior to other modes was supposed. The relation between height aspect ratio and failure mode are obtained by investigating the internal force distribution and bearing capacity of the cores. The flexural and shear capacity of the cores are calculated. The shear span ratio of the cores is obtained when flexural failure and shear failure occurred at the same time, and compared with that calculated from cores with common sizes. The result reveals that flexural failure is first to occur in the cores with high aspect ratio higher than 6.75.Theoretical analysis on displacement ductility of the cores under lateral load were carried out based on the assumption that the cores can be supposed as coupled walls with flanges. The formula for calculating displacement ductility was derived and it was expressed by the strength of coupling beams, the aspect ratio of pier, the axial compression ratio of pier as well as the ultimate compressive strain of concrete. According to the analysis results, a ductility design method of core was proposed.The dynamic analysis of the cores was carried out using the software of ABAQUS. The distribution of the plastic regions on the coupling beams and the plastic energy dissipation of the structure were studied. A new coupling beams arrangement method was proposed and it proposed that the strength of coupling beams at the middle height and enhancing those at the top and bottom height is proposed. The method was verified by the finite element analysis and it shows that the method could optimize the plastic state of the coupling beams at different height of the cores.