Dionysius Siringoringo

The rapid growth of Japanese economy during the 1960’s intensified construction of bridges and transportation infrastructures system to meet the expansion of industrial activities. Since then, the total infrastructure stocks have accumulated considerably. These include development of national railway line and the highway networks that are still continuing until now. In twenty years from now, the bridges constructed around seventies will be more than fifty years old. Without proper maintenance they will be deteriorating and degradating in function. It is anticipated that by the year 2020 the number of aging road bridges will constitute half of the total road bridge networks. Consequently, even though Japan has been long considered as a country that is active in new construction of infrastructures, maintenance has becoming an increasingly important issue nowadays.

Maintenance, however, is not only the issue for aging bridges and transportation infrastructures but also for the newly constructed ones. In order to maintain infrastructure condition continuously, comprehensive monitoring systems have been introduced at the beginning at its service life. Many newly constructed bridges especially the long-span ones are now being closely monitored. They are instrumented with embedded sensors that allow continuous –and in some cases, online monitoring. For smaller scale bridges, the monitoring process constitutes routine inspection using portable sensors. A routine inspection or an overall monitoring of bridge after certain severe natural environmental condition such as earthquake provides a tool to evaluate structures condition and to detect possible structural defects. For this purpose, the vibration based SHM is considered superior to other non-destructive assessment methods due to its characteristics that allow for global system monitoring as well as detection of local structural defects determined from changes in the vibration characteristics.

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