Health monitoring of highway bridges based on a Global Flexibility Index

Abstract

Structures such as bridges, buildings and infrastructure were constructed to serve society over an expected long period of time. Today, many of them have decayed due to aging, deterioration, misuse or lack of proper maintenance. It is important to be able to identify and monitor the health status of these structures to prevent potential sudden structural failures. The present study advocates monitoring of global weakening of the bridge structures. An index is proposed in this study for inferring the health deterioration of highway bridges, which shall be known as the Global Flexibility Index (GFI). This index is the spectral norm of the modal flexibility matrix obtained in association with selected reference points sensitive to the deformation of the bridge structure. The modal flexibility matrix can be evaluated from the dynamic responses at these reference points under forced vibration. A sharp increase in the index calls for further detailed investigation for appropriate actions. In this study, laboratory tests were conducted to demonstrate the sensitivity of the proposed index against different levels of controlled damages imposed on the tested structure, followed by a field test on an existing highway bridge.