抄録
Plasticity in steel is characterized by an appreciable amount of plastic flow which precede strain-hardening. This study is devoted to an evaluation of the out-of plane flexural rigidities of yielded steel plates at the instance of plate buckling. An emphasis is on the fact that a steel plate has finite values of flexural rigidities in this range due to the deformation restraint which is given rise to by the effects of support around the plate edges. Assuming that the stress-strain response of steel in this range follows the incremental plasticity theory for nonhardening material together with von Mises yield criterion, an explicit formulation are derived for the moduli to relate the flexural rigidities of plate. Comparison is made of the magnitude of so derived moduli with those in the strain-hardening range of mild steel. It is found that difference in the moduli between the both ranges is not significant from engeneering point of view. It is shown that column is a special case of plate and buckles when its tangent modulus vanishes. Local buckling of steel plate with its all four edges simply supported is examined by the moduli derived. And the difference of role of plastic flow and strain-hardening between column and plate is made clear.
