This paper describes the effects of material properties on the plastic deformation capacity of steel members. Now, mechanical properties of steel materials aren't reflected enough on the member design. So in this study, mechanical properties used to estimate the plastic deformation capacity of steel members are reexamined. As a result, it is pointed out that the stress in vicinity of yield point and the tangent modulus in the plastic region are important factor for decision of the plastic deformation capacity of steel members. Finally, estimate of plastic deformation capacity at the present are compared with estimate of plastic deformation capacity at the proposal in this study.
