The concrete-filled tube (CFT) column has the excellent structural performance. But it is difficult to connect with column and beam because of closed section. Its Solution, 2 members of ㄷchennel in which Internal diaphragm is installed were welded beforehand and the method of making Rectangular Steel Tube was proposed. According to upside and downside junction shape, Internal diaphragm suggested as symmetric specimen and asymmetric specimen. The upper and lower diaphragm of the Symmetric specimen used the same horizontal and The upper diaphragm of the Asymmetric specimen used the horizontal plate and the lower diaphragm used the vertically plate. In this research, 4 T-shape column to beam steps connections were tested with cyclic loading experiment in order to evaluate the structural capability of the offered connection. Symmetric specimens be a failure in 0.03rad from beam flange. And Asymmetric specimens be a failure in 0.05rad from column interface. The comparison results of All specimens shown similar to energy absorption capacity in 0.02rad.

The construction of a moment connection for a rectangular hollow section (RHS) column and a H-shaped beam is difficult because the RHS is a closed section. When a inner diaphragm is used for such a connection, in general, it is installed after cutting the HSS columns, which results in increased construction work. This paper suggests a new fabrication method to overcome such problems: An inner diaphragm is welded to inside a C-shaped section first, and then a column is fabricated by welding two C-shaped sections. This fabrication method is superior to a classic method in terms of constructibility. An experimental and a numerical study using Ansys 9.0 were performed in order to compare the strength of connections with respect to the presence of concrete, the corner shape of diaphragm, and the axis of loading. The experimental results including initial stiffness and ultimate loads are reported and the analytical results including load transfer mechanism, degree of stress concentration, and strain distribution are also reported.