The authors have conceived the buckling-restrained braces (BRBs) providing stable hysteretic behavior under the high-strain conditions. The compressive strength of BRBs generally tends to be higher than the tensile strength. The authors assumed that it was because of friction force between the surface of core plate and the restraining part, and that the magnitude of friction force was related to the buckling mode number resulting in the increase of contact points. A set of prediction formulas for the buckling mode number has been proposed in the authors' previous study. In this paper, the validity of the proposed formulas for the buckling mode number is examined by the test results of strain gauge measurement on the core plate from the cyclic axial-loading tests. Furthermore, the relationship between the strength ratio of the compressive to tensile strength and the slenderness ratio of plastic region of core plate is estimated. As a result, 1) the progress of the buckling mode shape is successfully observed from the test results, and 2) the proposed formulas correspond approximately to the upper and lower bounds of the buckling mode number and also estimate quite well the strength ratio from the test results.
