Abstract
The axial force in the columns as in the lower part of tall building frames may be considered for the elastoplastic deflection. In the begining the simplest elasto-plastic deflection behavior in a column subjected to axial force is analyzed and tabulated with P/P_e ratio where P is existing axial force and P_e is wellknown Euler load for the column when the both ends of which are assumed hinged. It is noticed that there is a critical load in the bilinear relationship between the horizontal load and the sidesway deflection because of the existing axial force. In this case the ratio between the load deflection modulus of elastic range and that of plastic range may be very roughly estimated as negative P/P_e ratio. Then an experimental study in a simple rigid frame is compared with the theoretical one. Finally the feature of elasto-plastic deflection characteristics such that the strain hardening effect disregarded in this paper is advantageous but the local buckling, which may occure in the flanges of members, may cancel out are discussed.
