DYNAMICS-BASED CONDITION ASSESSMENT OF A HIGHWAY BRIDGE TO ASSESS THE EFFECT OF UPGRADING

As part of an island-wide highway bridge upgrading program in Singapore an 18m span bridge was upgraded in a number of ways including conversion of nominal simple supports to a moment resisting connection. Before and after the upgrading, one-day modal testing exercises using a combination of forced and ambient vibration testing were used to identify the vibration modes up to 30Hz. The modes from the pre-upgrade exercise clearly reflected the orthotropic structural stiffness and the post-upgrade testing showed a very large increase in stiffness resulting from the changed boundary conditions and other additional features. The paper briefly describes the modal test procedure and the use of ERA in time and frequency domain to identify the vibration modes.