A ring tree is a tree graph with an optional additional edge that closes a unique cycle. Such a cycle is called a ring and the nodes on it are called ring nodes. The capacitated ring tree problem (CRTP) asks for a network of minimal overall edge cost that connects given customers to a depot by...

We study a new network design model combining ring and tree structures under capacity constraints. The solution topology of this capacitated ring tree problem (CRTP) is based on ring trees which are the union of trees and 1-trees. The objective is the minimization of edge costs but could also...

In this paper we present a heuristic framework that is based on mathematical programming to solve network design problems. Our techniques combine local branching with locally exact refinements. In an iterative strategy an existing solution is refined by solving restricted mixed integer programs...