Research On Mechanical Behavior Of Reinforced Three-side Fillet Welding Connections

Three-side fillet welding connection is widely used in the connection of joints in steel structures,because of the change of joint geometry,the stress distribution will be changed directly.In the joints of three-sided fillet weld,the toughness of the front fillet weld segment is weaker and the stiffness is high,under the influence of stress flow,the front fillet weld segment supports most of the joint load and will be destroyed first,while the side fillet welds do not reach their ultimate bearing capacities.At present,China's "Code for Design of Steel Structures"(GB50017-2017)does not make too many requirements for the design of the three-sided circumferential weld.By consulting the German "Code for Design of Steel Structures"(DIN18800-1),it is found that it proposes a different and new welding method for fillet weld connection of three-sided circumferential weld.The German specification clearly stipulates that the front fillet weld should be strengthened when the three-side fillet welding joint is used,that is,the foot size of the front fillet weld should be larger than that of the side fillet welds,and the transition parts between side fillet weld and front fillet weld are strengthened.In the design of the three-side circumferential welding given in the German "Code for Design of Steel Structures"(DIN18800-1),the strengthening of the front fillet weld and the end of the side fillet welds will indirectly affect the improvement of the load-bearing performance of the steel structures,the engineering community has should pay close attention to it.However,the understanding of this new type of connection is not enough,and the research on its mechanical behavior is also insufficient.Therefore,this thesis will focus on the mechanical properties of reinforced three-sided fillet welded joints proposed in the German code.The main research contents include:(1)Based on the finite element analysis software ABAQUS,and based on the data of the three-sided weld fillet connection test,a three-side fillet welding connection model was established and subjected to finite element calculation analysis,and then the finite element analysis results were compared with the test results.It is verified that the finite element analysis software ABAQUS establishes and analyzes the reliability and accuracy of the three-side fillet welding connection model.(2)Based on the finite element analysis software ABAQUS,the end seam reinforced three-sided fillet weld proposed by the German "Steel Structure Design Code"(DIN18800-1)and the non-reinforced three-sided fillet weld given in China's "Steel Structure Design Code"(GB50017-2017)Comparative analysis of fillet and weld joints.Through comparative analysis,it is found that under the same load,the stress value of the front fillet weld in the reinforced three-sided fillet weld joint is lower than the stress value of the front fillet weld in the non-reinforced three-sided fillet weld joint.In order to better overcome the common failure of the front fillet weld in the non-reinforced three-sided fillet weld connection,and further improve the connection bearing capacity.(3)Based on the finite element analysis software ABAQUS,and using the method of controlling single variable,this thesis research the strengthening position of the end-seam strengthened three-sided fillet weld joint,and analyzes the characteristics of its mechanical performance under different strengthening parameters.Through analysis,it is found that the increase in the size of the front fillet weld segment can increase the overall bearing capacity,but the size of fillet weld bead is too large,the stress distribution of the front fillet weld and the side fillet weld transition strengthened sections are uneven;the presence of the side fillet weld transition reinforced sections improve the bearing capacity of the overall connection,and the greater the length of the side fillet weld reinforced transition sections,the greater the overall connection carrying capacity;if the front fillet weld sections foot size increases the larger,the more obvious the role of the transition reinforcement sections of the side fillet weld.(4)Based on the finite element analysis software ABAQUS,the interaction mechanism between the welding seam segments in the end seam reinforced three-sided fillet welding connection is analyzed.Through the analysis,it is found that the transition reinforced sections and the non-transition reinforced sections in the side fillet weld have weakened the bearing capacity and strength of the front fillet weld section,while the front fillet weld section has their bearing capacity and strength values,and the larger the size of the welding feet of the front fillet weld section,the more obvious the improvement effect;if the length of the transition reinforced sections or non-transition reinforced sections of the side fillet weld are greater,the capacity of the front fillet weld section to their bearing capacity and strength value is weaker.