The identification of the main dynamic properties - frequencies, mode shapes and damping -is an important step in the analysis of existing structures and in the design of rehabilitation solutions. Dynamic tests are now frequently carried out on bridges to provide this type of data for numerical models calibration. Vibration frequencies and mode shapes are important parameters, but damping, which plays a crucial role in seismic analyses, is rarely the focus of reported experimental investigations. The accurate and repeatable evaluation of damping remains a challenge in dynamic testing. Ambient vibration test results have shown their limitations in this regard, and forced vibration tests are often the preferred method, when possible, to extract this key parameter. This paper presents a full-scale forced vibration test on a two-span reinforced concrete highway bridge in eastern Canada, located in a moderate seismicity zone. The objectives of the test are to quantify the damping of the bridge and to calibrate a three-dimensional model of the structure, developed with the Opensees platform. The forced vibrations required for the test are produced by a roller bearing shaker mounted on the bridge's deck and data are acquired using uniaxial velocity transducers. Two directions are investigated: vertical and transverse. The operating frequency of the shaker is varied with 0.05 Hz increments in a 2-17 Hz range to excite the first few modes and to create complete frequency response curves for the bridge, from which damping can then be accurately evaluated. The paper describes the experimental procedures, extracted structural properties and finite element model calibration.
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