Research On Mechanical Behavior And Design Method Of Eccentrically Braced Composite Frame With Vertical Shear Links

Compared with traditional ccentrically braced composite frame(“EBCF”),EBCF with veritical shear links has three advantages: the distribution of shear links is more flexible,the installation and dismantlement are more convenient,and the frame is more repairable.When the veitical shear links are made of low-yield-point steel(LYP steel),the energy dissipation capacity of the EBCF can be further improved.This dissertation investigates the mechanical behavior and design method of EBCF with vertical shear links.Through experimental study,numerical simulation and theoretical analysis,the working mechanism of the investigated structure is discovered,and a theoretical model and design method is provided for the structure.The research results can provide help for actual design practice.The research works of this dissertation are as follows:(1)An experimental research on 12 vertical shear links made up of LYP steel is conducted,the influence of the web thickness,flange plate,web stiffeners,web bucklingrestaining ribs,link length and link material on the failure mode,stiffnes,strength,ductility,cyclic hardening behavior and energy dissipation capacity of the shear links are investigated.Furthermore,an elaborate numerical model for the shear link is established to analyze its working mechanism.Based on the numerical model,the influence of the web aspect ratio and link length ratio on the stiffness,yield strength and hardening behavior of the shear link is quantitatively explained.Finally,a macroscopic spring element with new restoring force model is developed to accurately simulate the behavior of the shear links.(2)An experimental research on a composite frame and an EBCF with vertical shear links is conducted to investigate the influence of eccentric brace on the failure mode,stiffness,strength,stain development of different members,energy dissipation capacity and ductility of the composite frame.Futhermore,an elaborate numerical model and theoretical model is proposed for the EBCF with vertical shear links,which can accurately simulate the cyclic behavior of the structure.Based on the proposed model,a detailed analysis on the working mechanism of structure and influence of different design parameters on the structure is carried out.(3)The design method for EBCF with vertical shear links is given.Nonlinear timehistory analysis is conducted on an actual project structure to verify the efficiency of the design method and the superiority of the structure system.Furthermore,a genetic algorithm model is proposed for the optimization of brace distribution and link mechanical parameters,the results from actual practice show that,if the parameters of the genetic algorithm model is properly designed,the seismic performance and optimization efficiency can be further improved.