Condition evaluation for through and half-through arch bridges considering robustness of suspended deck systems

Abstract

Through and half-through arch bridges is one of the main bridge types in China, having arch ribs and simple suspended deck systems, which are connected by high-strength wire suspenders. However, due to the lack of robustness, the suspended deck systems of these types of bridges caused progressive collapse after the suspender corrosion damage. In this study, the internal structural factor of progressive collapse induced by suspender failure was revealed by comparison of five cases of suspender failure, and the robustness requirement of the suspended deck systems was proposed as redundancy to avoid transverse beam collapse when two supporting suspenders on both ends were broken at the same time. Meanwhile, a typical rigid-framed tied through concrete-filled steel tube arch bridge was investigated, and structural condition evaluation was carried out based on the Chinese standard (JTG/T H21-2011). It was found that the evaluation results of bridges with different deck systems were unreasonable, as the better the robustness was, the worse the condition of the deck system was rated, which would mislead the bridge maintenance decisions. A robustness-based evaluation method was then proposed by adopting different evaluation method according to the robustness of the suspended deck system, which is determined by qualitative classification or quantitative calculation. In addition, weight-adjusting method considering robustness was introduced in the evaluation process. The result showed that the new method could objectively reflect the condition of the bridge and thus fits the needs of bridge maintenance and management better.