Strength- and Component-Based Model for Steel Beam to Reinforced Concrete Column Joint

In recent years, substantial efforts have been made to incorporate the nonlinear behavior of joints in frame analysis. In this regard, a well-established component-based model (CBM) is provided in EN 1993-1-8 to capture the nonlinear moment–rotation curve of steel beam-column joints. In this paper, to extend the design approach in EN 1993-1-8 to steel beam-to-reinforced concrete column (RCS) joints, a simple mechanical model is first developed to determine the moment resistance of RCS joints. The proposed model can predict two different failure modes of RCS joints and yields better accuracy and consistency compared to the current design method for such joints. After determining the joint moment resistance, an appropriate CBM is developed to simulate the nonlinear moment–rotation response of RCS joints. The proposed CBM can capture the moment–rotation behavior of RCS joints at elastic, transitional, and ultimate states. The initial rotational stiffness of RCS joints can be easily calculated based on the proposed CBM. This is particularly important in the frame analysis as the beam-column joint can be classified as a rigid, semirigid, or pinned joint based on the initial rotational stiffness. The derivations are discussed in detail, followed by verifications of the proposed CBM. Compared to the experimental results, the proposed CBM shows reasonable accuracy in predicting the moment–rotation behavior of RCS joints. Most importantly, the numerical procedure of the proposed CBM can be implemented by a spreadsheet method, which provides a simple and robust means for structural engineers to obtain the mechanical properties of RCS joints.