General contact response of single-axle two-mass test vehicles for scanning bridge frequencies considering suspension effect

A general formula for the contact response of a single-axle, two-mass test vehicle considering the suspension effect is derived herein for scanning the bridge frequencies, which can be used not only for the simple beams adopted in the derivation, but for other beam-type bridges. It was known that the bridge frequencies in the vehicle spectrum directly obtained from the moving vehicle???s response are often masked by the vehicle???s self frequencies. This problem can be circumvented through use of the vehicle-bridge contact response that is born to be free of vehicle???s frequencies. It is with this in mind that closed-form solutions are newly derived for the vehicle???s body, wheel and contact responses, by treating the single-axle test vehicle as a two degree-of-freedom (DOF) model considering the suspension effect. The assumptions adopted in deriving the closed-form solutions can all be removed in the finite element simulation. The parametric study for simple beams indicates that: (1) the contact response given by the proposed formula (with or without vehicle damping) can be better used for frequency extraction than the vehicle response; (2) the wheel response is second to the contact response, but better than the body response, except for its susceptibility to pavement roughness; and (3) under the condition when most of the external factors are considered, the contact response has been demonstrated to be capable of detecting the first few frequencies of the bridge. Superscript/Subscript Available

Automated summary

This paper derives a general formula for the contact response of a single-axle, two-mass test vehicle considering the suspension effect, which can be applied to various beam-type bridges. The use of vehicle-bridge contact response can overcome the problem of bridge frequencies being masked by the vehicle's self frequencies. Closed-form solutions for the vehicle's body, wheel, and contact responses are newly derived, treating the test vehicle as a two degree-of-freedom model with suspension effect. The parametric study shows that the proposed formula is more effective for frequency extraction compared to the vehicle response, and the contact response is able to detect the first few frequencies of the bridge.