CFT Connections: State-of-the-art Report and Numerical Validation by 3D FEM

Connections between concrete filled members are common in tall buildings, bridges, and offshore structures because of their robust structural performance. While extensive research has been done on isolated concrete-filled structural members, relatively little research has been conducted on composite connection regions. This article first describes a database on experimental/analytical investigations on concrete-filled connections comprising 135 tests. It then develops a generic numerical model capable of capturing the entire range of behavior of these connections, including local buckling of the steel tubes and friction/contact resistance between steel and concrete. The model was calibrated against a single test and its performance was verified against three other very different tests. The results indicate that the four models can track well the strength and stiffness of the specimens up to ultimate and predict well different failure patterns. Comparisons of the experimental and numerical load-deformation curves show very good agreement in predicting the strength and deformations at which different behaviors arise, and that performance is controlled primarily by both the strength of the concrete and the confinement effect of the steel tube in the connection area.