A Lower Bound To Moderately Large Displacements Of Rigid-Plastic Structures

A method of bounding from below the load-displacement relation for rigid-plastic structures in stable post-yield ranges is discussed. Moderately large displacement theories are considered where strains involve terms nonlinear in stain gradients. The method employs the principle of virtual work, the convexity property of yield loci referred to the undeformed configuration of a structure and uses bounds to the internal dissipation. An explicit bound is given for plates and an example illustrating application of the method is presented.