Concrete filled steel tubular (CFT) columns have advantages in strength and ductility. Even under fire attacks, the core concrete could maintain its axial load capacity and thus the strict requirement for fire proof may be liberated. CFT columns have advantages over conventional type and RC columns because the steel tube serves as formwork and offers great confinement to the filled-concrete. As a result, strength and ductility under high axial load will be improved. However, the complex design and detailing for moment connections have to be further improved, simplified, and verified with experiments.
This research proposed a continuous beam flange type of the steel beam to circular CFT column connection. Four beam-column joint specimens are tested to examine the effect of filled-concrete, beam flange stiffeners, and width of beam flange on the joint shear strength. Construction of the specimen shows that the proposed connection details are practical and easy to be implemented. Cyclic loading test results show that the filled-concrete significantly increases the joint shear strength. The use of stiffener plates and increase of the flange width also have significant contribution to joint shear strength. In this research, the proposed shear strength calculation of the CFT beam column joint is based on the strength superposition principle of steel tube strength and concrete strength. The method for calculate the steel shear strength is based on the Von Mises yield criterion. While, the method for calculate the concrete shear strength is based on softened strut model with confinement effect consideration. The critical face of nodal zone is at the face which is in contact with the beam flange. Moreover, a method to evaluate the area of this face is affected by beam flange width, stiffener dimension, and column thickness. Furthermore, the prediction shear strength values are close to the test results, it means that this proposed method can be used to accurately evaluate the joint shear strength.

Concrete filled steel tubular (CFT) columns have advantages in strength and ductility. Even under fire attacks, the core concrete could maintain its axial load capacity and thus the strict requirement for fire proof may be liberated. CFT columns have advantages over conventional type and RC columns because the steel tube serves as formwork and offers great confinement to the filled-concrete. As a result, strength and ductility under high axial load will be improved. However, the complex design and detailing for moment connections have to be further improved, simplified, and verified with experiments.
This research proposed a continuous beam flange type of the steel beam to circular CFT column connection. Four beam-column joint specimens are tested to examine the effect of filled-concrete, beam flange stiffeners, and width of beam flange on the joint shear strength. Construction of the specimen shows that the proposed connection details are practical and easy to be implemented. Cyclic loading test results show that the filled-concrete significantly increases the joint shear strength. The use of stiffener plates and increase of the flange width also have significant contribution to joint shear strength. In this research, the proposed shear strength calculation of the CFT beam column joint is based on the strength superposition principle of steel tube strength and concrete strength. The method for calculate the steel shear strength is based on the Von Mises yield criterion. While, the method for calculate the concrete shear strength is based on softened strut model with confinement effect consideration. The critical face of nodal zone is at the face which is in contact with the beam flange. Moreover, a method to evaluate the area of this face is affected by beam flange width, stiffener dimension, and column thickness. Furthermore, the prediction shear strength values are close to the test results, it means that this proposed method can be used to accurately evaluate the joint shear strength.

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