Vibration-based dual-criteria approach for damage detection in arch bridges

Vibration characteristics of a structure can be used as an indication of its state of structural health as they vary if the structural health is affected by damage. This is the broad principle used in structural health monitoring for vibration-based damage detection of structures. Although most structures are built to have a long life span, they can incur damage due to many reasons. Early damage detection and appropriate retrofitting will enable the continued safe and efficient functioning of structures. This study develops and applies a dual-criteria method based on vibration characteristics to detect and locate damage in arch bridges. Steel arch bridges are one of the most aesthetically pleasing bridge types, which are reasonably popular in Australia and elsewhere. They exhibit three-dimensional and somewhat complex vibration characteristics that may not be suitable for traditional vibration-based damage detection methods. There have been relatively fewer studies on damage detection in these bridge types, and in particular the arch rib and struts, which are important structural components, have received little attention for damage detection. This study will address this research gap and treat the damage detection in the arch bridge structural components using the dual-criteria method to give unambiguous results. The proposed method is first validated by experimental data obtained from testing of a laboratory arch bridge model. The experimental results are also used to validate the modelling techniques and this is followed by damage detection studies on this bridge model as well as on a full-scale long-span arch bridge. Results demonstrate that the proposed dual-criteria method based on the two damage indices can detect and locate damage in the arch rib and vertical columns of deck-type arch bridges with considerable accuracy under a range of damage scenarios using only a few of the early modes of vibration.