Transmissibility performance of highly damped stationary vehicle and its contact-point response for indirect bridge health monitoring: Theory and experiment

Indirect bridge health monitoring is a promising measurement technique which has several advantages over the conventional direct method. However, the indirect method still encounters some challenges such as the effect of road roughness and vehicle’s own frequency. Utilizing the scanning vehicle in a stationary state has been proposed to overcome the effects of road roughness. Also, the contact-point response (CPR) has been developed to eliminate the vehicle’s own frequency. However, CPR has been developed for undamped vehicle. Therefore, the first part of this study develops CPR calculation method for a damped vehicle model. The CPR is calculated for a damped stationary vehicle (considering various vehicle frequencies) using the proposed equations. The transmissibility of the CPR is tested by comparing the time and frequency domains between the indirect (vehicle) and bridge direct response (reference). The transmissibility of the vehicle significantly improved by computing CPR, especially for low vehicle frequencies. In the second part of the paper, a frequency-free vehicle is developed in a laboratory set-up. The response of the vehicle does not contain the frequency of the vehicle due to using polyurethane (PU) wheels. Dynamic responses, damping ratios, and mode shapes are compared between the direct and indirect method. Accordingly, the results show that the designed vehicle has high transmissibility of the bridge vibration.