Research On Free Vibration And Seismic Behavior Of Frame-Core Tube Structures With Outriggers

With the rapid development of tall structures, frame-core tube structures with outriggers are widely being used in practical engineering. There are many cases that may be met if outriggers are set in structures.Thus, it is very significant for engineering design to study the mechanical behaviors and failure characteristics for this structure system.Therefore, based on forefathers'study achievements, following analysis is studied:Based on some assumptions, the free vibration frequency of the structures with one or two outriggers is analyzed. According to different values of the stiffness ratio of core-columns, the stiffness ratio of core-outrigger, and the stiffness ratios of tube and columns along structural height, the relation between the location of the outriggers and the free vibration frequency is inferred through a computer program. The equal-parameter distribution theory of the structural dynamics is used and the influences of core-tube's shear deformation, core walls and columns with changing stiffness and outrigger flexure are considered. The changes of the vibration frequency by core-tube's shear deformation are analyzed.Based on the finite element software ETABS, the effect of outriggers on the seismic response of a 50-story tall steel frame-reinforced concrete core tube structure is analyzed by building 3-D models. Structural horizontal displacement, drift angle ,the inner force of components and the distribution of inner force between inner tube and outer frame under earthquake are studied though changing hinged form, rigid form and semi-rigid connect etc joint connection forms between frame beams and core tube walls. The rational quantity and locations of outriggers are considered. Further research in elastic time history is presented on the influence of quantity of outriggers when outriggers are all setting in"reasonable locations". Nonlinear static of this structure is analyzed under rare earthquake by using software MIDAS/Gen. The sequence and location of plastic hinges, the effect for adjacent layers from outriggers and adjacent layers would be weakened or not are mainly studied in nonlinear static analysis. The comparison of structural capacity curves and the influence of P-â–³effect are obtained by nonlinear static analysis. Some conclusions about response characteristics and nonlinear static analysis of steel frame-reinforced concrete core tube structures with outriggers under rare earthquake are given.