Output-only Modal Identification and Model Updating of a Reinforced Concrete Bridge

ABSTRACT: This paper summarizes the application of a rational methodology for the assessment of older reinforced concrete Tunisian bridges. This methodology is based on ambient vibration measurement of the bridge, identification of the structure’s modal signature and finite element model updating. The selected case study is the SidiBouAli river bridge which is an eight-span simply supported bridge with a continuous slab. Each span has a length of 25 m and is supported by rubber bearings at the supports. Ambient vibration tests with output-only measurements were conducted on the bridge using a data acquisition system with nine force-balance accelerometers placed at selected locations of the bridge. The Enhanced Frequency Domain Decomposition technique, known to be robust with respect to the complex non-stationary nature of the unmeasured excitation, was applied to extract the dynamic characteristics of the bridge. For model updating, it was assumed that the parameters that can be changed in the model are the concrete modulus of elasticity and the rubber bearing stiffness. The first parameter indicates any possible damage in the bridge and the second parameter reflects the changes in boundary conditions. The application of the proposed methodology led to a relatively faithful linear elastic finite element model of the selected bridge