Limit analysis of frictional block assemblies as a mathematical program with complementarity constraints

The computation of the collapse loads of discrete rigid block systems, char acterized by frictional (nonassociative) and tensionless contact interfaces , is formulated and solved as a special constrained optimization problem kn own as a Mathematical Program with Equilibrium Constraints (MPEC). In the p resent instance, some of the essential constraints are defined by a complem entarity system involving the orthogonality of two sign-constrained vectors . Due to its intrinsic complexity, MPECs are computationally very hard to s olve. In this paper, we investigate a simple numerical scheme, involving ap propriate relaxation of the complementarity term, to solve this nonstandard limit analysis problem. Some computational results are presented to illust rate potentialities of the method. (C) 2000 Elsevier Science Ltd. All right s reserved.