Study On Seismic Performance Of Steel Frame Asymmetric Haunch Plate Enhanced Node

The strengthening of steel frame beam column joints has been the research hotspot of domestic and foreign experts in recent years. Its working principle is to strengthen the cross section of the beam, forcing the plastic hinges positioned the end of reinforcing section where are away from the beam-column connection weld location, protect the weak part of the joints effectively, improve the seismic behavior of the joints, which reached the design thought of the “strong node weak component”.This article has designed three cruciform unsymmetrical axillary enhanced node specimens, an experimental study was carried out for the three nodes under cyclic loading, and finite element numerical simulation was carried out for them. Analysis and comparison of failure mode, ductility performance and energy dissipation capacity which has been calculated by experimental study and finite element simulation. Take one of the nodes as the basic specimen, establishment seven finite element models by changing the thickness of the plate, the thickness of the stiffener which setting by the beam-end web, and the size of the weld holes. Analysis and comparison the influence of mechanical properties by these constructing variable. The main conclusions are as follows:Firstly, three cruciform unsymmetrical axillary enhanced node specimens do not occur overall instability of structures under cyclic loading, but two of them appear brittle fracture. The main cause of stress concentrate phenomenon is that the size of the weld holes too much, and the welding heat-affected zone between the liner and the top flange which make the steel brittle, thus the brittle fracture of the specimens is made in the region.Secondly, the failure mode of the finite element analysis relatively close the experimental results, show that the reliability and accuracy of the finite element analysis results. But there is great difference between the hysteretic behavior, energy dissipation capacity and stiffness degradation of the joint and the experimental results, which is due to the machining defects of specimen, initial eccentricity of the component, quality defect of weld, welding residual stress and other incidental factors, and Load eccentricity, sensitivity of displacement meter is relatively small, the frictional force by steel beam end and the lateral bracing, and the frictional force by the vertical hoisting jack and joint specimens in the test.Thirdly, the plastic hinge external shift mechanism of the unsymmetrical axillary enhanced node is not ideal, thus establishing the corresponding model of symmetrical axillary enhanced node, and comparative study on them, show that, the plastic hinge external shift mechanism of the symmetrical axillary enhanced node is more efficient.Fourthly, this paper carry out the finite element analysis for mechanical properties of the joints by changing the thickness of the plate, the thickness of the stiffener which setting by the beam-end web, and the size of the weld holes. conclusion that, the influence to the mechanical properties of the joints by changing the thickness of the plate is very little. the influence to the ductility factor and plastic rotation angle of the joints by changing the thickness of the stiffener which setting by the beam-end web, and the size of the weld holes are greatly.