Seismic Design And Automatic Optimization Method Of Braced Mega Frame-Core Tube Structure

Recently,a large number of super-high-rise buildings have been constructed in the seismic regions in China,that makes the seismic performance of super high-rise structures to become a common focus of engineering applications and academic research.The braced mega frame-core tube structure is a novel kind of super-high-rise structural system.Referring to the structural layout of Shenzhen Ping An Financial Center and Tianjin Goldin Financial 117 Building,the FEM models of the braced mega frame-core tube structure system were established.The seismic responses of the models under earthquakes were systematically studied.The structural performances,including deformations,component damage,energy dissipation,fragility analysis and collapse-resistant capacities,were researched to clarify the influence of ratios of inner and outer tube stiffness,stiffness contributions of mega braces,and outrigger trusses.Finally,the automatic optimization design methods of the structural system were studied.The main research contents are as follows:(1)Through the comparison of the novel braced mega frame-core tube structural system and the conventional mega frame-core tube-outrigger truss structural system,the structural behaviors including the typical yielding sequence,component damage characteristics,the relationships of shear force and moment were studied and clarified.The braced mega frame-core tube is a kind of hybird structures with superior seismic performance,which is suitable for super high-rise buildings of more than 500 m.(2)Based on the nonlinear dynamic time-history analysis,the influence of seismic performance under different structural characteristics including ratios of inner and outer tube stiffness,stiffness contributions of mega braces,and outrigger trusses were analyzed.(3)Adopting the IDA-based seismic fragility analysis,collapse probabilities and collapse-resistant capacities were quantitatively evaluated on structures with different ratios of inner and outer tube stiffness,stiffness contributions of mega braces,and outrigger trusses.The ratios of inner-outer tube stiffness and the contribution proportion of mega brace stiffness are negative correlated with the structural collapse-resistant capacities.The establishment of outrigger truss would lead to the decrease of the structural collapse-resistant capacity.The seismic design recommendations based on uniform collapse risk were proposed for the braced mega frame-core tube structural system.(4)With the simplified braced mega frame-core tube structure as the research object,the running environment of distributed parallel computing based on LAN are developed.The mathematical model of structural optimization was established with the minimum material cost as the objective function and the specification requirements as the constraints,including inter story drift ratio and axial compression ratio et al.From the perspectives of optimization criteria,mathematical method and intelligent algorithms,the automatic optimization methods based on the equal incremental sensitivity,Hooke-Jeeves algorithm(HJ),genetic algorithm(GA),particle swarm optimization(PSO),ant colony optimization(ACO),artificial bee colony(ABC)and gray wolf optimization(GWO)were proposed.And their effectiveness and feasibility of proposed methods were verified by optimization examples.