Study On The Collapse Simulation And Seismic Performance Of Super Tall Mega Column-Core Tube-Outrigger Buildings

In recent years, a large number of super tall buildings are constructed in seismicregions of China, and more attentions are focused on the seismic performance of thesuper tall buildings. The mega column-core tube-outrigger structure is a typical andwidely used structural system in recently designed super tall buildings. As arepresentative super tall building, the Shanghai Tower with a total height of632m isstudied herein, based on which a series of investigation is on the collapse simulation andseismic performance of the super tall buildings subjected to extreme earthquakes areconducted. Four key issues, including (a) the collapse simulation of super tall buildingssubjected to extreme earthquakes,(b) the selection of the rational ground motionintensity measure,(c) the energy dissipation of Shanghai Tower at different seismicintensities, and (d) the influence of the minimum base shear force on the seismicperformance of super tall buildings, are studied in some detail in this dissertation. Thefollowing summarises the main achievements made throughout this study.(1) An analysis method of the collapse simulation for super tall buildings subjectedto extreme earthquakes is successfully proposed. Take the Shanghai Tower as thespecific research object, a rational finite element model is established using MSC.Marc2007and some key issues of the modeling are discussed in some detail. Subsequently,the potential collapse process of Shanghai Tower subjected to extreme earthquakes issimulated with the elemental deactivation subroutine UACTIVE based on the materialconstitutive law. The simulation results provides a better understanding on the damagepropagation and collapse mechanisms of super tall building subjected to extremeearthquakes.(2) A novel ground motion intensity measure for the seismic design of super tallbuilding is proposed. After reviewing the existing ground motion intensity measuresand considering the contribution of high-order vibration modes to the overallperformance of the super tall buildings, a ground motion intensity measure based on thegeometrical means of the elastic spectrum acceleration is proposed. Rational value ofthe key parameter associated with this intensity measure is suggested on the basis of a series of time history analyses. This proposed intensity measure can effectively reducethe dispersion of the structural seismic response for super tall buildings.(3) The seismic energy dissipation principles in the mega column-coretube-outrigger structure are systematically studied. Through a series of time historyanalysis of Shanghai Tower under different seismic intensities, the energy dissipationcharacteristics are evaluated. The results indicate that the total earthquake energy ofShanghai Tower is dissipated by the structural damping itself and the structural plasticenergy dissipation is dominant in the upper4zones. Note that the outrigger is one of themost important and ideal plastic energy dissipation components. Damage of the upperzones due to the high-order vibration modes can be reduced by the installation of theadditional viscous dampers on the outriggers. The inclusion of dampers also leads tomore uniform lateral deformation of the whole structure. To this end, this aspect ofresearch has provided useful references for damage control of super tall buildings.(4) The influence of the minimum base shear force on the seismic performance ofsuper tall building is discussed. Three different super tall buildings are designedaccording to three different minimum base shear force specifications recommended byvarious design codes. Elasto-plastic analysis and collapse analysis are conducted, andthe influence of the minimum base shear force on the seismic performance of super tallbuildings is discussed in some detail. This aspect of research with valuable outcomesmay contribute to further development of optimum design for super tall buildings.