Enhancement of product capabilities at the conceptual design phase is an important issue when developing high performance mechanical products. Maximizing the range of conceptual and basic ideas concerning essential structural and mechanical design features improves the likelihood of successful results at the conceptual design phase, since these features directly affect fundamental product performances. This paper discusses a new design support method based on structural optimization techniques, for use at the conceptual design phase, which assists the decision-making of design engineers working to obtain innovative and high performance mechanical structures. To achieve this, a new concept of structural discrete elements is introduced, namely, "function-oriented elements", defined as structural elements that have a specific function, intentionally implemented by a design engineer in order to clarify insights concerning the achieved optimality of the optimal mechanical structures from a mechanics point of view. Finally, several numerical examples confirm the validity and utility of the proposed method, which should offer useful support to mechanical design engineers at the conceptual design phase.