| With the vigorous development of prefabricated steel structures in my country,various new prefabricated steel beam-column joints have emerged in response to the situation.Most of these beam-column joints are semi-rigid joints.The current steel structure design specifications(standards)have no clear calculation methods and regulations for this type of joints.The use of the current specifications not only fails to make full use of the characteristics of the joints,but also causes possible waste of resources or structural safety.At present,there are many researches on solid-web T-plate connection semi-rigid joints at home and abroad,but the research on lattice connecting beam-column joints is obviously insufficient.Based on this situation,the research group conducted research on the proposed fabricated lattice beam-column joints through quasi-static experiments and finite element simulation analysis,and achieved certain results.Based on the existing research,this paper changed the beam and column channel steel to asymmetric design,designed 8 groups of members,used channel steel thickness and bolt diameter as control parameters,carried out finite element simulation of monotonous loading,and studied the improved initial stiffness of the joint and the ultimate load,the force mechanism of the joint is analyzed,and a simplified calculation model of the joint is proposed.Based on the component method,the calculation formula of the initial stiffness and the prediction of the bearing capacity are given.The main conclusions of this paper are as follows:(1)The damage of the joints mainly occurs in the channel steel on the upper side of the tension end.The yield of the beam I-channel steel spreads from the vicinity of the bolt hole to the surrounding;the inner side of the channel steel increases with the increase of the bolt diameter,the position where the yield occurs is closer to the bolt hole.The yield of column I-channel steel is approaching from both ends to the vicinity of the bolt hole.(2)Increasing the thickness of the channel steel and the increase of the bolt diameter can improve the initial stiffness and ultimate bearing capacity of the joint.When the channel steel has a large thickness,increasing the bolt diameter is not effective when the ultimate bending moment is not small in thickness,but when the channel steel has a small thickness,the increase in the ultimate bearing capacity loses a certain degree of ductility.(3)This paper proposes that the improved joint is a semi-rigid joint according to European standards.The rotation center of the joint in the elastic stage is located near the lower bolt of the abdominal channel steel.Under the ultimate load,the rotation center is located near the lower pressure end channel steel bolt.By analyzing the distribution of normal stress and shear stress of the channel steel section at the tensile end,the calculation of channel steel should not adopt the classical beam theory,and the shear lag effect should be considered,so the plate and shell theory should be used for calculation.(4)In this paper,the component method is used for stiffness assembly,and the relationship between the load and deformation of the channel steel at the upper side of the beam and the column is derived.The comparison with the finite element solution shows that the initial stiffness has a larger error when the channel steel is small.For other thicknesses,the error is between 1% and 8%,and the prediction of the ultimate bearing capacity is about 12% when the channel steel thickness is large.The theoretical formula can better reflect the performance of the joint. |
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