Damage Assessment of a Prestressed Simply Supported Bridge using Microwave Interferometer

The microwave interferometer was used for monitoring the behavior of a simply supported bridge under various loading cases. The instrument has a 1-D imaging capability for remotely measuring the displacements of multiple positions simultaneously. The loading cases include truck placed at the middle of the span, driven with variant speeds to generate ambient vibration of the span, driven through with a constant speed, and abruptly stopped at the middle to obtain the damping characteristics of the span. As the bridge has been in operation for 50 years, weak bearing stiffness for the support at abutment and possible fatigue fracture of a roller support above a pier was found from this investigation.