Abstract: The structural performance of existing reinforced concrete (RC) bridge gradually deteriorates due to concrete cracking and reinforcement corrosion. Based on experimental study on two 28-year-old existing reinforced concrete arch ribs, the load-displacement and load-strain relationships, the residual load carrying capacity and the failure pattern are explored. Some factors influencing their ultimate strength are analyzed. The constitutive relationship of aged concrete is presented. Finite element model was developed to analyze the ultimate strength of RC arch rib with the consideration of material aging and structural damage. As a comparison, the undamaged and geometrically perfect arch rib is also analyzed. A comparison between the experimental and FEA results is made. It can be concluded that the initial cracks, the reinforcement corrosion and the variation of the arch axial line shape have great influences on the ultimate strength and failure mode.