Structural capacities of tension side for CFT square column-to-beam connections with combined-cross diaphragm

The purpose of this study is to suggest a new CFT column-to-beam connection type, which will have an axis direction that takes into consideration the asymmetry of connections. Through experimental study and finite element analysis, the study also compares the structural capacities of the new CFT column-to-beam connection type with those of existing connection types. Existing connection types for comparative study are those with an interior diaphragm and through diaphragm. The new connection type suggested uses a combined-cross diaphragm, featuring a column flange penetration in the major-axis direction and an interior diaphragm in the minor-axis direction. In order to analyze and compare the initial stiffness and strengths of the connections considered simple tension tests along with finite element analysis were performed on the specimens, while idealizing the tension-applied beam flange. Stress concentrations, according to the geometric configurations and load transfer mechanisms of diaphragms, were analyzed through finite element analysis. The results show that the existing connection types, in terms of initial stiffness and ultimate strength, do not precede the combined-cross diaphragm, and that the stress concentration on the connection can be relieved by improvement to the detail.