The paper proposes a procedure for shape optimization of flexible soil-steel structures. The mechanical behaviour of such structures is significantly different in comparison to other bridge construction technologies. The load bearing capacity of the backfill soil is of the key importance. This fact was taken into account. In particular, the energy optimality condition and simulated annealing algorithm were utilized. Due to the assumptions made, while originally formulating the condition, the optimal shapes should be regarded as the ones maximizing backfill mobilization. Thus, the method takes the advantage of the peculiar character of soil-steel structures and, therefore, should be regarded as specially dedicated to such type of engineering objects. A detailed formulation of the procedure is followed by a short review of the optimization results obtained by the author so far. In this regard two types of load were considered: dead-weight of the backfill and uniformly distributed load of the surface. However, the original contribution of the work is a proposal of the procedure modification allowing to identify the optimal shape of the shell of a soil-steel structure capable of carrying the moving load, i.e. without it being necessary to assume a priori the location of the vehicle. To achieve this the “worst case” logic was applied to modify optimality condition. The optimal shapes, obtained numerically for different types of loading including non-stationary truck load, and the relations between them suggest the potential for the practical use of the proposed optimization procedure.