Study On Mechanical Behaviors Of Beam-to-column Connection With Stiffened Top And Seat Angles

Top and seat angle connections in steel frames have been widely used in Europe and United States,the stiffeners are generally not added at the angle in order to simplify the construction.But in China,stiffeners are welded in angle to strengthen the connection.The mechanical behaviors of stiffened angle and un-stiffened angle are quite different.They are few studied about the static property,hysteretic property and seismic performance in domestic and foreign,so there is a lack of experimental research,calculation method and theory of this type connection.The current calculation method of initial stiffness and strength of unstiffened type connection is generally large deviation.Further more,the ultimate bearing capacity and ultimate displacement of top and seat angle connections is also an urgent need to analyze and in the evaluation under quasi static and impact loads.In view of the above problems,the main contents of this paper include that:(1)Eight top and seat angle joints with different geometric construction were tested under monotonic loading,the influence of stiffener location and joint direction and compared with the un-stiffened type.Twelve T angle type connections were conduct under static tensile force.The influences of the pretightening force in high strength bolt,stiffeners and the length of the angle on the tensile stiffness and bearing capacity of the T angle type connections were analyzed.(2)Finite element numerical simulation was used to analyze the static loading specimens,and various element types and calculation methods are compared,and the stress mechanism of each connection part was analyzed and verified.60 connection models of T type angle connection and 30 top and seat angles joints were established.According to the results of parameter analysis,important parameters affecting the moment bending characteristics of connections were extracted.A finite element model of 6 large-size top and seat angle joints and 12 large-size angle T type angle connection were established.The force law of large-size angles and bolts was summarized.The bearing capacity calculation method of large size angle and the distribution rule of dislocated row bolts are suggested.(3)The arm selection method in calculating the initial stiffness and flexural capacity was based on the analysis of test results and parameter study.The calculation method of initial stiffness and flexural capacity were put forward for un-stiffened and stiffend top and seat angle.and the corresponding design method and suggestion were put forward according to the force characteristic of the joints.(4)Four top and bottom angle steel connections with different construction were tested under cyclic loading,and some key seismic performance indexes such as failure development mode,ultimate bearing capacity,energy dissipation capacity and ductility of connections were evaluated.(5)A finite element model considered ductile damage and strain rate was analyzed under quasi-static load and impact load.Several failure modes and key parameter that affected quasi static stress process were obtained in numerical analysis,and the calculation formula of ultimate tensile force and ultimate displacement is proposed,compared the force mechanism of impact load and quasi-static process,three key parameters affecting the connection stress under impact load were analysed.