A theoretical method based on upper bound theorem to analyze ultimate strength of reinforced concrete columns is proposed. A yield line which crosses the extreme compression edge of a member end is assumed. As the angle of the yield line is varied, the yield line and the strength of the smallest strength are considered to be the predicted solutions, when a yield criterion of reinforced concrete sections considering interaction of combined forces being used. The predicted solutions by the proposed method show good correlation with test results of 26 reinforced columns. The method is also compared with conventional methods. By these examinations, the usefulness of the method is shown. Additionally, it is cleared that the amount of reinforcements has a great influence on the angle of yield lines.
