It became possible to predict and trace elasto-plastic behaviors of unbonded braces by the finite elements method taking the material and geometrical non-linearity into considerration in which unbonding effect was modeled by "tying method". (1) Regarding the relationship of the load and the axial displacement and of the load and the horizontal displacement, there is good agreements between analytical and experimental results in the characteristics of hysteresis curves, although analytical values eive larger values than experimental values because (1)Bauschinger's effect of steel was disregarded, (2)stiffness of mortar after the occurrence of cracking was evaluated on the stiffer side, (3)local fracture of end mortal was disregarded, and (4)steel's yield point after large cyclic strain was evaluated on the high side in the mixed hardening rule of steel material. (2) There is good agreement between analytical and experimental results regarding the characteristics in stress and strain distribution and hysteresis charachteristics of core steel plates.
