This paper address a practical life-cycle cost (LCC) formulation and procedure for the LCC-effective optimum design of steel bridges. A general LCC model for optimum design of steel bridges consists of those of initial cost and direct/indirect rehabilitation costs of a steel bridge, including repair/replacement costs, loss of contents or fatality and injury losses, road user costs, and indirect socio-economic losses. Thus, this paper focuses on the presentation of a general formulation of LCC models and LCC-effective design system models for steel bridges suitable for practical implementation. Especially, based on previous research, a new road user cost model and regional socio-economic losses model are proposed. Then, in order to demonstrate the LCC-effectiveness for the design of steel bridges, illustrative design examples of actual steel box girder and orthotropic steel deck bridges are discussed. From the results of the numerical investigation, it may be positively stated that the LCC-effective optimum design of steel bridges based on the LCC model proposed in this study will lead to a more rational, economical and safer design compared with the initial cost optimum design as well as the conventional design.