In this paper, first, elastic buckling behavior of the plane frames subjected to horizontal loads is discussed in detail using a numerical analysis. Then, it is shown that, story drift angle smaller than 1/200 by horizontal loads have no influence on column buckling length. Following conclusions come out from above and past knowledge. When we design with the Japanese first level designing seismic load, the buckling length of column in plane frames can be shorter than member length. And we propose the calculation method for the buckling length of column in plane frames. It is a method for the buckling mode without member angle.
