If an interior RC joint (with a sufficient amount of stirrup) was tested with cyclic loading and there was a major crack in the joint, the end of that diagonal crack continued to propagate into the column as a vertical crack causing the splitting and separation of the joint and column's concrete cover.

so what could be the cause of this? I thought there might be some slippage occurrence or buckling of the column bar there. But it seems like the column longitudinal bar doesn't yield yet