The requirements of unbonded brace cover are mainly classified into two factors which are stiffness and shear strength. Those factors should be satisfied simultaneously for the brace to attain the yield strength. Even if stiffness requirement of unbonded brace cover is satisfied, shear failure sometimes occurs at the end of the unbonded brace cover. The purpose of this paper is to investigate how the shear stress occurs in the unbonded brace cover. The shear occurrence mechanism is clarified by the consideration of the steel brace behavior in the cover. The obtained results are verified through a series of experiments.
