Estimating Bridge Modal Parameters from Residual Response of Two-Connected Vehicles

Purpose: This study presents a method to estimate the bridge frequencies, damping ratios and mode shapes from the responses of two connected single-axle vehicles. As the bridge pavement roughness is the main excitation for a passing vehicle, the roughness-related components can seriously overshadow the bridge modal parameters contained in the vehicle responses. Although the residual response from two-connected vehicles has been adopted to remove the roughness-related components in the identification of bridge frequencies, the estimation of bridge damping ratios and mode shapes from the residual response is not fully explored yet. Methods: A semi-analytical solution is first derived to understand the frequency content of a contact-point residual response; then, the two contact-point responses are back-calculated from the vehicle responses. Subsequently, the singular spectrum analysis is conducted to exact the bridge frequency-related mono-components, from which the bridge damping ratios are estimated by curve-fitting while the mode shapes are constructed by Hilbert transform. Results: The numerical results show that the proposed method enables the estimation of the first two bridge damping ratios and the construction of the first mode shape with satisfactory accuracy. Conclusion: The proposed method can effectively remove the adverse effect of pavement roughness and efficiently construct the mode shapes of bridge in consideration of bridge damping ratios.