Effect of strain hardening on the buckling of structural members and design codes recommendations

Some aspects of buckling behaviour of structural elements made of nonlinear materials with strain hardening, for which the stress–strain law has no yield plateau (stainless steels, aluminium alloys and others) are discussed. Considering compressed bars and plates made of materials with linear and nonlinear strain hardening, on the basis of tangent modulus theory and the deformation theory, we show that there exists a “threshold” value of the hardening factor below which the hardening does not influence the limit load. But if the hardening factor exceeds the threshold value then the hardening significantly increases the limit load and this increasing is not properly accounted for in some worldwide design codes.