This paper investigates the structural performance of an improved detail in the through-diaphragm system for steel tubular column-beam joints, developed to enhance fabrication efficiency. The proposed system integrates the bracket-flange with the through-diaphragm, thereby eliminating the need for full-penetration welding between the beam flange and the diaphragm. In order to clarify the structural performance and plastic deformation capacity of the proposed system, static cyclic loading tests were conducted on six specimens. Furthermore, a method for evaluating member classification applicable to the proposed system is also discussed and verified through comparison with experimental results.
