Vibration Tests and Damage Detection of p/c Bridges

A three-span countryside bridge with simply supported P/C girders has been found to have excessive deflections in two of the three spans. It is reported that the prestresses in tendons of two girders of different spans are lower than design values. This was determined after performing compression tests of concrete core samples, measuring deflections and performing corresponding analysis. This actual bridge provides valuable specimens for studies of damage detection using vibration test data. The objectives of the present study are (a) to prove experimentally that the changes of dynamic characteristics of a bridge can be used as an indicator for damage detection and (b) to study the possibility of application of system identification in defining damage quantitatively. It is found that the changes of mode shapes can be used as an indicator for damage detection. In addition, the use of system identification allows successful quantification of the damaged members in the P/C bridge.