Forced and ambient vibration testing of a permanently instrumented full-scale bridge

A 25-span bridge was one bridge recently constructed along the I-15 corridor in Salt Lake City, Utah. The test section continuously spans four concrete bents over a total length of 183.52 meters. Testing of this bridge provided an opportunity to analyze the bridge's natural frequencies and mode shapes from both forced and ambient vibrations. An eccentric mass-shaking machine induced the horizontal forced vibration. Local traffic, wind, and other sources produced the ambient vibration. Data were collected through a series of accelerometer and seismometer arrays. The analyzed data provide a baseline for possible post-earthquake testing to determine deterioration or seismic damage of the bridge. The ambient vibration data are being continuously monitored over the long term to investigate trends in the bridge response. This paper presents the natural frequencies and mode shapes determined for the structure and compare them for each day data were recorded.