An Age- and Condition-Dependent Variable Weight Model for Performance Evaluation of Bridge Systems

Abstract

To address the balance problem between indexes within the performance evaluation of bridge systems, this paper develops an age- and condition-based variable weight model (ACVWM). First, the limitations of existing models used for the multi-layer weighted sum method, i.e., constant weight model (CWM) and condition-based variable weight model (CVWM), are presented through case studies, indicating that the weight variation is insufficient to characterize the deterioration law of components. Then, the definition of age-based variable weight is established following the existing concept of condition-based variable weight, which makes weights vary with service ages. Considering the characteristics of bridge assessment, an age-based variable weight model is built up to depict the time-variant trends of index weights with the service age. The variation law of age-based variable weight is discussed by using indexes in the superstructure of suspension bridges. As a result, the weights of replaceable and permanent components behave differently within the bridge service life. Finally, the ACVWM is built up and its effectiveness is verified through the same case studies applied to the CWM and CVWM. Compared with the evaluation results from the CWM and CVWM, the evaluation result of the ACVWM is more in line with the real maintenance strategy. Considering the CVWM in which low initial weights may lead to unsatisfactory weight assignment, the advantage of the proposed ACVWM lies in its capability to adjust initial weights over the service age.