Experimental Investigation of a Bridge under Traffic Loadings

Abstract

A set of dynamic field tests were conducted on the Chulitna River Bridge recently. The Chulitna River Bridge, built in 1970, is located at Historic Mile Post 133 on the Parks Highway between Fairbanks and Anchorage, Alaska. Ambient free-decay response approach is used to estimate the dynamic properties of the bridge. Stationary and dynamic tests on the acceleration responses of the bridge recorded at different locations and in different directions during traveling vehicle passing the bridge. The natural frequencies are identified are characterized by the FFT methods. Results show that there are several components at 1.50, 2.20, 2.85, 3.23, 4.58 Hz are characterized, 2.85, 3.23, 4.58 Hz are bridge vertical mode; 1.50, 2.20 Hz are the longitudinal mode of bridge. Compared with the finite element model results, the measured results matched very well. The modal parameters identified from the bridge responses recorded at different locations are compared with each other to check their consistency, and are compared with FEM analytical results. The results demonstrated that (1) the modal parameters consistent with the FEM results; (2) The modal frequencies results are very sensitive to measurement locations, as such, multiple measurement points are necessary, and the optimization of measurement location is critical to conduct the test efficiently; (3). The identified modal properties of the Chulitna River Bridge could be used as benchmark in on-going health monitoring studies of this bridge.