Monitoring changes in vibrations can identify hidden damage in bridges, said a Queensland University of Technology researcher who has developed an effective long-term method for monitoring bridge safety. PhD engineering researcher Henry Shih's method can determine whether a bridge is damaged and even locate where the damage is in the structure.

Shih said it was important to monitor the health of bridges so they could be appropriately maintained. This method can be used to ensure the structure is safe, and if there is any damage detected, it can be fixed. The method used data obtained from the vibration monitoring of the bridge. The data collected is fed into a specially designed computer model which could identify any damage in the bridge.

Bridges vibrate from impacts and also from ambient factors such as normal traffic and wind. "In my research, I have tested the hypothesis by modelling the vibrations of small-scale steel bridges, both in their healthy and damaged states," explains Shih. "The vibration data changed when the bridges were damaged and the computer model confirmed there was damage and indicated where the damage was located."

This method could be applied to many bridges in Brisbane and Australia. "It is best to have permanent instruments on bridges which continuously monitor changes in their vibrations," he adds. "This would be a long-term monitoring system."