A load-carrying capacity curve of cruciform column high Mn projection panel (Mn panel) assembled by structural steels and high Mn steel was obtained. In elastic buckling, the ultimate strength of Mn panel assembled by dissimilar steels was nearly equal to that of Mn panel assembled by similar steels. However, in elastic-plastic buckling, both of the ultimate strengths were different. Whichever similar steels or dissimilar steels might be assembled, the stress-displacement behavior of each projection panel was same as that of steel itself, when the existed steel structures were repaired or reinforced, the use of the steels whose strength is higher than that of the present steel makes the ultimate strength of the existed structures higher.
