Dynamic Characteristics of an Overpass Bridge in a Full-Scale Destructive Test

Abstract

Verification of vibration-based damage detection through a full-scale actual structural testing is an important learning opportunity. From such a test, the evolution of dynamic characteristics can be observed, damage detection methods can be validated, and baseline criteria for typical structural damage can be formulated. This paper describes a case study on a full-scale destructive testing of an overpass reinforced concrete bridge. Damage is introduced by cutting one of the bridge piers at the footing level allowing vertical settlement. This type of damage is expected to simulate the condition in which a bridge suffers from nonuniform pier settlement or hidden damage inside piles of buried foundations. By applying time and frequency domain vibration analysis, as well as a system identification technique, changes in dynamic characteristics caused by the damage are evaluated. The results clearly indicate the changes in frequencies as an indicator of damage presence, while the change in mode shapes can be used to locate the damage. The paper also discusses the application of the damage detection method based on outlier analysis of the autospectra function using the bridge ambient acceleration responses. The results indicate that the presence of damage at an early stage can be detected by observing the outliers in multivariate data, and the detection accuracy improved when damage has significantly changed the dynamic characteristics of the structure.