Abstract: In order to accurately assess the reliability of the stay cables， which are vulnerable and difficult to repair， and to ensure a safety and comfort driving， a reliability evaluation method on stay cables based on cloud theory was proposed. According to the mechanical characteristics and common defects of cables， a reliability evaluation index system of stay cables was established by selecting indexes using the extreme stress value， amplitude of constant load， stress amplitude， basic frequency， service time， cracking degree of PE sheath and integrity of the damping system. Then the weight cloud models were established according to experts′ opinions， and the group decision weights were obtained from the concept extension of general concept tree. Finally， a weighted summary was conducted on the average certainty of assessment grade for each index and the weight cloud model. The certainty cloud models of each reliable grade thus can be obtained to determine the final result. The rationality and maneuverability of the method were verified by comparing the specification evaluation results with the actual defect condition.

Key words: cloud theory, stay cables, reliability evaluation, index system, general concept tree