Analytical models for predicting the load-bearing strength of beam-to-column joints in a composite steel frame

Two analytical models are developed to predict the load-bearing capacity of a beam-to-column joint inside a slim-floor composite frame. The load inside the joint is transferred mainly by a steel console welded to a concrete-filled steel column. Because of the asymmetric nature of plastic collapse mechanism of the steel console, a two-parameter model is developed in two mechanisms: a mechanism excluding the axial force at hinge lines, and an intuitive mechanism including the influence of arising axial force. The models are verified by numerical results and used further for parametric studies. The results indicate that both models predict the limit load of the joint well. The studies also show that the model excluding the normal force is simple to use but can be a bit conservative, whereas the model including the normal force better predicts the load-bearing capacity of the joint, particularly if larger indentation is allowed. Based on the parametric studies, a general equation is then proposed. Compared to the method provided in design code as EN 1993-1-8, the proposed equation predicts the higher load-bearing capacity; thus leading to a more economical design in practice.