Research On Optimization Method Of Steel Frame Structure System With End-plate Connection Base On Failure Mode Control

With good seismic performance,the steel frame structure system with end-plates connection is commonly applied to buildings in high seismicity areas.When the beam-column members of the structure are connected through the end-plates and high-strength bolts,there will be significant nonlinear deformation in the beam-column connection area under the action of seismic load,resulting in high discreteness of the failure mode of the overall structure.Given this problem,the current seismic code advocates the structural failure mode control design by adjusting the "strong column and weak beam" coefficient through internal force adjustment,and the basic concept is "strengthen-strengthen-re-strengthen".However,this is not the most economical method,nor should it be the only way to control failure modes.Therefore,this paper takes the end-plate connected steel frame structure system as the research object,based on the in-depth study of the failure mode of the structural system,an optimization method to effectively control the structural failure mode is proposed,which has important reference value for the improvement of the current design method.The main research work of this paper is as follows:(1)The failure modes of semi-rigid joints considering panel zone deformation are studied.The seismic behavior of end-plate connections and T-stub connections are studied by analyzing the shear deformation principle of the panel zone.The shear-deformation curve model of the panel zone is discussed and verified by comparison with experimental results.At the same time,the failure modes and energy dissipation characteristics of the two kinds of joints in each loading stage are discussed.Based on the analysis results,a calculation model of semi-rigid joints considering the deformation of node domain is proposed,which provides a prerequisite for the performance calculation of steel frame with end plate connection.(2)The experimental study on failure mode of steel frame with end-plate connection is completed.The failure process,bearing capacity,ductility and energy dissipation capacity of the frame at different stages are discussed through experimental study.Finally,the finite element software ABAQUS was used to verify the failure mode and performance of the frame,and the thickness ratio of endplates to column flanges was parameterized to discuss the influence of the thickness ratio on the performance of the whole frame,and the failure path of endplate connected steel frame structure was given,which provided a basis for the research in the following chapters.(3)The performance calculation of steel frame based on the characteristics of end-plate connection joints is carried out.Based on the previous research on the connection and panel zone,the component method is used to calculate the rotation characteristics of the end-plate connection,and the characteristics are embedded into the overall frame for performance calculation and compared with the test results of two one story and one two-story end-plate connection spatial frames.At the same time,the connection model considering the deformation of the panel zone is embedded into the frame for time history analysis to verify the accuracy of the node calculation model.(4)The optimization method of steel frame structure system with end-plate connection based on failure mode control is studied.Based on the research results of connection and subframes,the end-plate connection database was established,and the failure mode control theory considering node stiffness was deduced.Based on the elite reserved genetic algorithm(EGA)developed in Python language,the optimization method of end-plate connection steel frame based on failure mode control was studied,and the global failure path and seismic performance of the frame were verified by Open Sees nonlinear analysis.