Damage Evaluation of Truss Bridges Using a Reliability-Based Assessment Technique

This paper presents an investigation on damage evaluation of truss bridges using long-term measurement data of strain. A reliability-based method is proposed for structural damage evaluation, in which the safety index of each structural member is assessed making use of the long-term monitoring data of strain and reliability analysis; subsequently an examination of the change in safety index before and after damage is made to identify the damaged member(s). The proposed method possesses two salient merits: (i) it directly uses long-term measurement data of strain for damage evaluation without need of structural model, and (ii) it provides quantitative information to bridge managers for decision making on optimizing and prioritizing bridge inspection and maintenance. This paper focuses on the study of: (i) the effect of damage on structural member safety index for determinate and indeterminate truss bridges, respectively, (ii) the influence of inconsistent loading levels before and after damage on the evaluated safety index, and (iii) the influence of different probability distribution types (normal, lognormal, and mixed) of the load effect and resistance on the evaluated safety index. Some important conclusions are obtained from the study.