Advanced TOPSIS Approach to Variable Index Weighting in Bridge Condition Assessment

As the service age of bridges increases, the degeneration of the bridge components leads to changes in the importance of corresponding state assessment indices. Employing fixed weights in bridge service condition assessments may result in inconsistent outcomes with the actual conditions. Therefore, this paper proposes an index weight updating method that aims to achieve index weight updating based on the operational status of bridges, thereby enhancing the accuracy of bridge service condition assessment results. This method utilizes the bidirectional projection of fuzzy numbers representing index state intervals and ideal targets as the technique for order preference by similarity to an ideal solution (TOPSIS) evaluation criteria for index importance. This paper conducts case analyses of a suspension bridge across multiple service periods which comprise three primary conditions: periods of intact bridge status, suboptimal conditions resembling expected degradation, and damaged status due to external effects. The case study results demonstrate that the updated weight using the proposed method effectively reflects the influence of actual changes in bridge status on the importance of indices. In the cases of good condition or matching the expected degradative state, the updated weights obtained could better reflect the actual service condition of the bridge compared to fixed weights provided by standards. When considering the effect of accidents or other incidental factors, the updated weights obtained through the proposed method could reflect the influence of actual component conditions on the importance of indices while the initial weights and age-dependent updated weights cannot. Thereby, the assessment results derived from this approach are more consistent with expected states and maintenance levels, validating its effectiveness and comparative advantages over alternative methodologies. The results indicate that the proposed method can significantly enhance the rationality of assessment index weights, serving as a more effective and rational approach for evaluating bridge service conditions.