| The connection of steel frame has an important impact on seismic performance. There were a massive of brittle failure happened on the traditional connections during the Northridge Earthquake and the Kobe Earthquake. After these earthquakes, amounts of experts endeavored to the traditional nodes’research and analysis and have found two kinds of new ductile joints-the ’enhanced node’ and the ’weakened node’. Although both of them have been widely used on the engineering, these two types of connections are complex and expensive. At the same time, along with the popularization and application of high strength steel the ability of flexion and plastic deformation have been inevitably weakened as well as the energy dissipation effects. This paper presents a new type of composite steel joints which locally change the web by low strength steel plate with the same thickness, and the other flanges and webs are full of high strength steel. In this way, the web with low strength would form plastic hinge under a strong earthquake to absorb more energy.Firstly, determine the range of low-strength steel webs’ location and length according to the distribution characteristics of the internal force under both vertical and horizontal loads. What is more, to compare the effects on seismic performance between different low-strength steel web the grade of steel is also regard as one of the parameters. Then, the numerical simulation analysis of unidirectional loading and cyclic loading on 18 specimens was analyzed respectively by finite element analysis software ANSYS to discuss the effects of position, strength, length and stiffeners of the replaced low strength steel web on combination of steel beam-column bolted and welded joints’ stress properties and the seismic performance of the impact force. Through the research results on the simulation, it is found that the desired capacities could be achieved by replacing some part of the web by low strength steel. Although the composited steel beam column nodes’ bearing capacity is slightly decreased but the seismic performance is greatly improved. The web with low strength steel could form plastic hinge to protect the connection. The best distance from the low steel web to the end of beam is 0.5～0.75 of the height of the beam. The proper replace length on the new type joints of the web can range between 1.5-2.0 of the height of the beam. The strength of the replaced web has a great effect on the connection’s capacity. The proper yield ratio between low strength and high strength steel is between 0.6 and 0.7. To move the plastic hinge away from the connection it is better not set stiffening rib on the low strength web. |
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