The transformation of the building sector towards sustainability represents one of the key engineering challenges of this century. Focusing on the mechanical efficiency of the structural design is one way to achieve this goal. Numerical structural optimization offers an extensive tool kit for the drafting of improved designs. This study treats the special aspects of numerical topology optimization in civil engineering using the example of bridge design. A typical optimization task in this context, its characteristics and solution method, that is based on mathematical programming, are presented. The load transfer of the optimized structures is investigated and evaluated in terms of mechanical efficiency, their realization is discussed.