Time-Varying Reliability Analysis of Corroded Bridge Cables Based on Fuzzy Failure Criteria

The increasingly prominent durability problem of bridge cables not only leads to costly replacement but also causes safety concerns. This paper studies the time-varying reliability of corroded bridge cables through considering fuzzy failuare criterion. Firstly, the resistance degradation model of the corroded cable is established based on the corrosion rate of the steel wire and the corrosion propagation law of the cable section. Then, a time-varying reliability model of cable corrosion considering fuzzy failure criterion is proposed based on safety factor and the fuzziness of cable failure in operation period. A case study was carried out to compare the proposed model and the one with clear failure criterion with considering the time-varying reliability of service cable under different corrosion environment. The results show that the proposed model can reflect the variation of cable reliability in different corrosion environment and service time. Compared with the clear failure criterion, the gradual change rule of time-varying reliability index under the fuzzy failure criterion is better and is more consistent with the engineering practice. It avoids the difficulty in selecting the safety factor under the clear failure criterion at a certain degree. The time-varying reliability index of corroded cables has obvious time division, and it gradually decreases with the corrosion degree of steel wires. The service life of the cable with local sheath damage is only 8-10 years. Due to the irreversibility of steel wire corrosion, avoiding sheath damage and strengthening early flaw detection capability are the key to ensure the cable durability.