Field investigation of fundamental frequency of bridges using ambient vibration measurements

The transient nature of forces induced in structures during earthquakes requires the use of dynamic analyses to fully characterise their behaviour. A modal analysis describes the dynamic response of the structural system through modal descriptors: natural frequencies, mode shapes and damping ratios. Efficiently estimating these modal parameters for bridges allows for better structural integrity assessments and structural health monitoring of these structures. Using ambient vibration measurements to estimate modal parameters is time-saving and efficient. This research reviews the literature on the application of ambient vibration testing to the modal characterisation of bridges. Natural frequencies from ambient vibration measurements are obtained for a typical bridge in the City of Montreal in Canada.;The MATLAB computing platform is used to execute spectral analyses of the field measurements. Linear, analytical models of the bridges are constructed with the SAP2000 structural analysis programme and Eigenvalue analyses are performed. The experimental and analytical results are compared and discussed, followed by recommendations for the application of this procedure to other bridges in the Montreal region.