When tensile type bolted joints are used in bridge structures, these joints have multiple bolt rows to resist a large sectional force. However, it is known that strength of tensile type bolted joints with multiple bolt rows are less than the strength for the number of bolts. This study focuses on a stiffener to improve the strength of tensile type joint with multiple bolt rows, and conducted these joints' experiment and FE analysis. The one of the obtained results is that the set of stiffeners is effective in getting the joint proof strength and the joint yield strength for the number of bolts. Additionally, installing the stiffener can improve the strength with less weight rather than increasing the joint flange thickness in tensile joints with multiple bolt rows.
