Study on the Influence of Connection Configuration on Composite Joints

Steel–concrete composite joints possess higher bearing capacity, initial stiffness and redundancy than bare steel joints. The configuration of beam-column connection would influence the behavior of composite joints, such as rigidity, rotation capacity and so on. In this paper, the test of two fully welded rigid composite joints and two flush endplate semi-rigid composite joints was introduced. The loading conditions in the tests involved sagging moment and hogging moment. The mechanical behavior of composite joints under bending moment was studied in detail, especially on the influence of connection configuration. The test results indicated that the experimental phenomena and failure mode of fully welded composite joint and flush endplate composite joint under hogging moment were similar to each other. The buckling of bottom flange of steel beam determined the behavior of composite joint under hogging moment, such as initial stiffness and bending strength. It indicated that using flush endplate connection instead of fully welded connection in composite joints had little influence on the behavior of the joint under service loads if the failure mode of joints is governed by the same component. Four models for moment-rotation relation of composite joints are compared with experimental results. Based on the comparison, a new combination model of power function expression and linear expression is developed. With proper optimum shape parameter and descending stiffness, the new model could present the moment-rotation relation of composite joints, regardless of connection configuration or loading condition.