Study On Seismic Performance Of Flange Expanded Web Opening Joints

With the continuous improvement of modern science and technology and the growing national economy,people pay more and more attention to sustainable development and green development,and people’s understanding of sustainable development is also deepening.However,the traditional construction method not only has a serious impact on the urban environment,but also has a great impact on the urban environment,and can no longer meet the development requirements of the times..Compared with the traditional structural form,the steel structure building structure can realize the concept of green and sustainable development,which is one of the main structural forms used in the new era.One of the core issues of steel structure is the study of joints.So far,the research on frame beam-column joints is mainly divided into two directions.One is the reinforced joint,and the other is the weakened joint.Both methods have their own advantages,but there are also some shortcomings.In view of some problems existing in the two kinds of joints,this paper designs a new type of beam-column joints,and uses reinforced and weakened joints to establish a finite element model for variable parameter analysis.The main research contents and conclusions are as follows :(1)The flange-expanded web-perforated joints are designed by using the direct-expanded-wing joints in the reinforced joints and the web-perforated joints in the weakened joints.The mechanical properties and energy dissipation capacity of 22 specimens are analyzed by changing four parameters,and the reasonable range of each parameter is obtained.The results show that the opening radius has the most significant effect on the mechanical performance of the specimens.The energy dissipation capacity and ductility of the joints can be improved by increasing the opening distance appropriately.It is recommended to take the value in the range of0.15 ～ 0.35 times beam height.The influence of the two parameters of the opening distance and the size of the expanded flange on the mechanical performance of the joint is not particularly significant.Appropriately increasing the opening distance can slightly increase the bearing capacity of the joint,but too large distance will weaken the ductility and energy dissipation capacity of the joint.The optimal distance of the opening should be controlled between 0.7 and 1 times the beam height,and the maximum should not exceed 1.2 times the beam height.(2)In order to improve the stress concentration of the flange at the root of the beam and the premature buckling of the web,a new type of flange-expanded web open-hole joint with stiffeners on the beam web is designed,and 12 specimen models are established.The corresponding parameters of the data results are compared and analyzed,and the variable parameter analysis of the new joint is carried out to study the influence of the stiffener on the mechanical performance of the new joint.The relationship between the ratio of the stiffener spacing to the opening radius and the mechanical performance of the joint is studied,and the recommended value range is given.The results show that the flange with stiffeners on both sides of the web opening can improve the stress concentration at the flange of the beam root to a certain extent.By comparing the mechanical performance and energy dissipation capacity of each specimen,the best recommended value range of the opening radius of the new joint is 0.2 ～ 0.25 times the beam height,the ratio of the stiffener spacing and the opening radius L / R is set as the proportional coefficient,and the L / R is 4.2～ 5.The stress concentration at the root of the beam is improved,the phenomenon of premature buckling of the web is also improved,and the bearing capacity and ductility of the joint are improved to a certain extent,and the energy dissipation capacity is good.(3)An elastic-plastic time history analysis of a steel frame with flange expanded web openings was conducted.Three seismic wave curves were selected according to the requirements,and the inter story displacement,base shear force distribution,and stress strain state of the frame under earthquake action were studied.Under load,the joints may undergo plastic deformation to a certain extent,but the entire structure still has good toughness and energy dissipation capacity.The plastic strain at the joints is small,reflecting the role of strengthening the flange,which indicates that the joint has successfully reduced the stress concentration phenomenon at the beam column connection.This means that in practical applications,this joint can be used as an effective joint method to improve the toughness and seismic performance of the structure while ensuring its strength.