Abstract:The tie rod is a key component in the bowstring arch bridge, which is used to balance the horizontal thrust at the arch feet. Its long-term performance directly affects the safety and durability of the bridge structure. Taking the Wuxi Huaqing Bridge under the operation for 20 years as the research object, and targeted on multiple diseases in its flexible tie rod system, two representative tie rods are selected to conduct the on-site inspections and systematic laboratory mechanical performance tests. The results show that the internal steel strands of tie rod are in good condition, the galvanized layer is intact and the rust grade is Grade I. However, the efficiency coefficient of the static load anchoring performance of the entire cable is only 0.91, and the percentage of total elongation is 1.2%, all being lower than the standard requirements. The fatigue life of the whole cable is only 50% of the design expectation, and the steel strands break after about one million cycles. The further analysis indicates that the performance degradation of tie rod is mainly due to the failure of the sealing in the anchoring zone, which leads to long-term water accumulation inside, causing rust on the anchor and a decrease in the grip force of the clamping plates, as well as stress concentration caused by the bent anchoring structure at the arch foot. The performance degradation rate of single-strand steel wire materials is relatively slow, and the deterioration of the whole cable is mostly dominated by systemic factors.
