Nonlinear finite-element-analysis and design of steel-concrete composite ring (SCCR) joints

Conventional steel-plates-strengthened-composite ring (SPSC) joints are extensively used in composite structures to connect concrete-filled tubular (CFT) columns and reinforced concrete (RC) beams. However, the refinancing-bars of the adjacent beams require on-site welding to the steel strengthened plates of the SPSC joint, which, regarding workmanship, is difficult and time-consuming. Recently, a new type of joint, the steel-concrete-composite-ring (SCCR) joint, has been proposed as a substitute for the SPSC joint since it has been successfully used in several construction projects in Hong Kong. An SCCR joint consists of a steel tube, a concrete ring beam with reinforcements in both the radial and hoop directions, and shear studs. This research develops a sophisticated Finite-Element (FE) modelling method for SCCR joints, where the dominant factors affecting the joint's behaviors are considered, such as the explicit simulation of the complex reinforced bar details and shear studs, the cracking and crushing of concrete, the yielding of reinforced bars, and the contact behaviors between the steel tube and the concrete. From the FE analysis results, four possible failure modes are identified. Parametric studies are sequentially conducted in regard to these modes, yielding corresponding design eqs. A design procedure developed through the proposed equations is illustrated with a flowchart. Finally, a real-world example project is presented and further validated by sophisticated FE analysis.