ABSTRACT
R. P. WEST and A. J. O'CONNOR Department of Civil, Structural and Environmental Engineering, Trinity College Dublin, Ireland
Abstract The techniques of mathematical optimisation are well suited to the problem of plastic analysis and design of structural frames. Indeed, it is well known that the basic structural relations of statics, kinematics and the constitutive relations naturally formulate themselves into the Kuhn-Tucker conditions necessary for optimality. Thus in plastic limit analysis or synthesis, one proceeds directly to the point of collapse, where the collapse load is assumed to be unique, and the conventional simplex algorithm can readily produce solutions. However, in the elastoplastic region of loading, the assumption of load path independence may no longer be valid and plastic hinge unstressing may occur, even under a monotonic loading regime. While techniques exist to allow for this, the extent of this effect is not well known and even a simple two span beam can have surprising behaviour prior to collapse.
