Download or read book System Identification of Highway Bridges Using Long-term Vibration Monitoring Data written by Hugo C. Gomez and published by . This book was released on 2011 with total page 241 pages. Available in PDF, EPUB and Kindle. Book excerpt: The need for maintenance and protection of critical highway infrastructure links has led in recent years to significant developments in the area of bridge structural health monitoring. Taking advantage of the instrumentation of three highway bridges located in Southern California, this dissertation focuses on the application of system identification (SI) techniques to a database consisting of more than 2,000 data sets collected over a period of nine years. The data sets consist of ambient and traffic induced vibration records, earthquake records, and controlled vehicles test data. During the controlled vehicle tests acceleration transducers were mounted on the vehicle chassis to study the potential for bridge identification using instrumented vehicles. It is demonstrated long-term monitoring needs to be conducted in a permanent or periodic basis in combination with the application of SI techniques for the purpose of identifying changes in structural response characteristics and material properties due to aging factors and earthquake intensity. The ambient and traffic-induced vibration data were analyzed using the frequency domain decomposition technique for identification of modal parameters, i.e. natural frequencies and mode shapes. For a five-year period, a reduction of the first natural frequency is found to be approximately 2% for a 3-span straight bridge, 5% for a 3-span highly curved bridge and 3% for a four-span slightly curved bridge. Using seismic acceleration records, the bridge modal parameters are identified using time domain SI techniques. It is found the identified first frequency of one of the bridges decreases up to 20% during an earthquake of moderate intensity (PGA> 0.37g) with epicenter close (