Research On Optimal Design Of Semi-rigid End-plate Connection And Application In Steel Frame Design

As a widely used form of steel structure beam-column connection,end-plate connection has a certain rotational stiffness and is a typical semi-rigid connection.However,in practice,the design of semi-rigid end-plate connections encounters difficulties due to the lack of mature design methods and design tools.End-plate connections are often designed according to rigid connections,which is disadvantageous to the structure considered from the aspects of structural safety and economy.The design of beam-column semi-rigid end-plate connections is a complex problem involving multi-parameters.Different combinations of structural parameters such as end plate thickness,end plate width,bolt diameter,bolt row number and bolt spacing will result in different stiffness,bending bearing capacity and cost of joints.Therefore,it is necessary to study the optimal design method of end-plate joints in order to facilitate the application of endplate joints in the design of steel frames.In view of the above problems,the main research contents of this paper include:(1)On the basis of the existing research,the component method for calculating the flexural bearing capacity and initial rotational stiffness of semi-rigid end-plate connections is combed,and the fast calculation of flexural bearing capacity and initial rotational stiffness is realized by self-programming.Combined with the moment-rotation curve model of semi-rigid connections,the calculation programs of moment-rotation curves of different types of end-plate connections are developed.(2)Based on the experimental or FEM results of 22 specimens,the differences of different calculation methods of initial rotational stiffness of end-plate joints are compared and the appropriate calculation method is selected.The fitting conditions of different moment-rotation curve models are compared and analyzed,and the mathematical model suitable for describing the moment-rotation curve of semi-rigid end-plate connections is selected.(3)Taking the cost of semi-rigid end-plate connections as the goal and the requirements of connection stiffness and bending yield bearing capacity as constraints,the optimization problem of semi-rigid end-plate connections is established.The improved genetic algorithm is used to solve the optimization problem,finally realize the optimal design of many types of endplate connections.(4)On the basis of the optimization design of semi-rigid end-plate connections,a semirigid steel frame design process combined with joint optimization is proposed to solve the problem that joint design and beam-column design are the premise of semi-rigid steel frame design.The effectiveness of this method is proved by the design of a single-story and threestory semi-rigid steel frame.(5)From the point of view of the optimal stress of frame beams,the relationship between the fixity factor,bearing capacity and cost,the reasonable value of the fixity factor in semi-rigid steel frame design is explored,and some preliminary suggestions are given.