The basic design criterion for reinforced concrete structures in Japan is in a limit state design format. However, the customary Allowable Stress Design method has been used for reinforced concrete bridges. The purpose of this study is to develop the method of estimating optimum load factors for reinforced concrete bridges. The distributions of the bending moments arising from wheel loads at slabs and beams respectively, are estimated by using Monte Carlo simulation. Examples are presented for highway bridges both of Hanshin Express-way and Tokyo bay Route. The results obtained here show that both TL-20 and TT-43 loadings should be modified. In addition, some methods in calculating reliabilities of structures are proposed.
