The design optimization of RC structures should take into account the uncertainties related to all, material properties, geometry, loading and deterioration. The Time-Variant Reliability-Based Design Optimization (TV-RBDO) consists in finding the optimal design by satisfying appropriate safety level during the whole structure lifetime. This work proposes an efficient method for TV-RBDO, where the classical formulation is transformed into a sequence of equivalent deterministic design optimization sub-problems. This trans-formation is defined by the mean of optimally calibrated safety factors, linking the reliability requirement to the equivalent deterministic optimization. The proposed method is developed to account for deterioration (corrosion) and is applied to optimize a corroded RC bridge girder. The results show the effectiveness and the efficiency of the method.