Pretensioning Suspender System for Performance Improvement of a Tied-Arch Bridge with PC Stiff Hangers

This paper investigates the improvement method and evaluation process for the service performance of a prestressed concrete (PC)-stiffened tied-arch bridge, of which the bearing capacity can be easily degraded due to aging of its components. A reasonable and effective active retrofitting technology is proposed, and high-strength steel strands are used as new pretensioned flexible suspenders, which are added to the original bridge structure through a new connector design. To validate the performance of the retrofitting method, an efficient and stable retrofitting evaluation process is established based on the experimental data obtained from tests carried out on a typical damaged tie-arch bridge in China. To assess the effectiveness of the retrofitting method, the values of the static performance index, dynamic performance index, and pedestrian comfort index before and after retrofitting are compared. Analysis of the results for the static performance index indicate that the retrofitting method can achieve ideal effects and effectively improve the performance of the original concrete stiff hangers, which exhibit excessive tensile stress before retrofitting. The dynamic performance demonstrates that the retrofitting method can improve the structural stiffness and effectively alleviate the excessive dynamic response of the original bridge. Furthermore, the pedestrian comfort index is improved after retrofitting. Overall, the proposed approach of this paper can effectively aid in the management and maintenance of a PC-stiffened tied-arch bridge.