In the United States, past research on composite frames has focused on the nodes of reinforced concrete columns and steel beams. In a typical structural system consisting of reinforced concrete columns and steel beams, small sections of steel are built into the column, mainly for ease of construction rather than for force transmission. Other studies have shown that innovative structural measures using post-tensioning and bolting provide sufficient strength and ductility for a pure steel or casing concrete bending frame. The research on seismic performance of steel-reinforced concrete columns and steel beam joints is still less <1,2>. Through a project funded by the National Natural Science Foundation of the United States, Uang and Chou tested two full-length steel-concrete columns and steel beam assemblies to evaluate the seismic performance of their joint structures <3,4>. In the test, the joint structure with a weakened steel beam section and a stiffened plate showed great potential in seismic resistance. However, the node construction studied by Uang et al. is still very complicated because it requires steel beams and columns to be joined by field welding.
The proposed connection method of steel-reinforced concrete column-steel beam bending frame is to improve the maneuverability while ensuring excellent seismic performance. The main researchers in this paper have conceived several innovative combined connection structures. It is proposed to develop a new combined steel-hybrid bending frame system that uses end plate bolting without field welding. Three specific connection methods are proposed here: the non-energized end plate bolt connection between the steel reinforced concrete column and the steel beam is as shown in (a), the steel beam has a welded end plate at the factory, and the end plate is bolted and The flange of the column steel is connected. The transmission of the bending moment depends on the high-strength tensile bolts, stirrups and concrete supports connecting the steel beam end plates and the built-in steel columns. Both the stiffener and the continuous plate can be used. If necessary, stiffeners can also be used. The construction process of this type of structure is as follows: 1) placing the steel column; 2) connecting the steel beam end plate with the steel column by bolts; 3) tying the column steel; 4) making and pouring the column (and plate) concrete.
Suggested design methods The selection of test pieces is recommended by the ability design method. The method comprises the following steps: 1) selecting a mechanism for the plastic hinge to appear at the end of the steel beam and the base of the first column; 2) designing a concrete or steel reinforced concrete column with sufficient bending and shear strength to Ensure the implementation of this mechanism; 3) design the end plate and select the appropriate bolt; 4) the shear verification of the beam-column joint, which complies with two criteria: (1) by comparing the main tensile stress of the joint with the tensile strength of the concrete Size, to determine whether the joint concrete will crack; (2) If it is determined in (1) that the joint concrete will crack, further bracing and ferrule analysis to determine how to enhance the shear resistance of the joint.
Conclusion The steel beam-concrete composite bending frame system with innovative joint structure is the research object proposed in this research plan. The proposed joints are pre-welded to the end plates and columns of the steel beams by bolting. The columns here may be reinforced concrete columns, prefabricated columns, and reinforced concrete columns.
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