Automatic recognation and real-time alarming of eerthquake induced vibration of a tied arch bridge

China is heavily suffered from various types of natural disasters, such as earthquakes and typhoons. This paper presents the monitoring and recognizing of seismic responses of a tied arch bridge, which has been installed with a long-term structural health monitoring system since November 2007 in Hangzhou, China. Wenchuan earthquake (Magnitude 8.0) occurred at 14:28 (China standard time) on May 12, 2008, in Sichuan province of China. The earthquake was felt in the city of Hangzhou-about 1,600 kilometres away-where bridges and office buildings swayed with the tremor. The bridge health monitoring system successfully monitored the structural responses due to the earthquake. About two-minute abrupt changes in displacement amplitude were observed in the measured signals starting at 14:37, about 9 minutes later than the earthquake´s occurring. In order to achieve the real-time alarming of extreme events, such as earthquakes, typhoons, and collisions, this paper proposes a Euclidean distance based recognition method to compare the variation rate of seismic response data with preset thresholds calculated from the normal response data. Using the proposed method, the displacement responses under excitation of Wenchuan earthquake are successfully recognized and the real time alarming is thus realized.