Critical evaluation of factors on extracting multiple bridge frequencies from drive-by measurements

The drive-by monitoring technique for bridge dynamic properties extraction from the vibration response of the instrumented test vehicle presents several practical benefits. In this paper, a detailed numerical parametric study is conducted to investigate the individual and combined effect of critical factors such as vehicle frequency (dependent on vehicle mass and vehicle stiffness), vehicle damping, vehicle speed, bridge surface roughness, and ongoing traffic on extracting multiple bridge frequencies from the moving vehicle responses. This study helps in providing guidelines for designing a robust field drive-by test vehicle applicable to the majority of bridges and to develop a reliable vehicle scanning method for bridge damage diagnosis. From the numerical investigations, the results show that the identification of multiple bridge frequencies from the response of the test vehicle is largely possible when the vehicle is designed with a frequency greater than the interested higher bridge frequency. Low vehicle speed is recommended to reduce the camel hump phenomenon observed at higher bridge frequencies. Due to the absence of the overshadowing effect of vehicle frequency, high vehicle damping and contact point response serve as a better feature to capture significant dynamics of the bridge. The ongoing traffic suppresses the high-frequency components generated by bridge surface roughness and proves beneficial for the extraction of multiple bridge frequencies.