Structural health monitoring of a bridge with energy dissipators

After natural events like the 1994 Northridge (USA), the 1995 Kobe (Japan), the 1999 Chi-Chi (Taiwan) and the 1999 Duzce (Turkey) earthquakes it became evident that the demand for bridge structures could greatly benefit from the application of isolation/energy dissipation techniques. Despite the level of maturity achieved in the field of seismic isolation, open questions still remain on the durability of seismic response modification devices (SRMD) under working conditions. The option of removal of sample devices from the bridge structure to verify their performance characteristics involves a significant economical effort, particularly if associated to disruption of the regular traffic. It provides also a device response verification difficult to correlate to the global structural performance. Health monitoring techniques offer a valuable alternative. The main objective of this research is the definition of an effective health monitoring approach to be applied to bridges protected with the most common seismic response modification devices (SRMD). The proposed methodology was validated with the use of records from a bridge equipped with viscous dampers. The record were obtained before and after damage occurred. The procedure proved to be accurate in detecting early degradations of the device characteristics as well as of the structural elements directly connected to the devices.