Peculiarities in Optimal Redundancy for a Bridge Network

The pecularities associated with the problem of redundancy optimization of a bridge network are illustrated. The interconnecting branch (which makes the network non series-parallel) apparently has no influence on the redundancy optimization. The optimization process always 'strengthens' one of the second-order paths, irrespective of individual subsystem costs and constraints. Thus we are, in effect, solving a series-parallel system.