Theoretical and Experimental Verifications of Bridge Frequency Using Indirect Method

Abstract

According to the idea of indirect bridge frequency measurement proposed by Yang and co-workers (J Sound Vib 272(3–5), 471–493, 2004; Eng Struct 27(13), 1865–1878, 2005; Smart Struct Syst 13(5), 797–819, 2014), a moving test vehicle can be regarded as a message receiver to detect vibration data of the bridge that it passed. In the present study, an experimental setup will be carried out for indirect frequency measurement of a simply supported beam using a passing test vehicle with the feature of adjustable frequencies. The test vehicle is design as a single-degree-of-freedom unit in vertical vibration and guided by a set of tensile strings in self-equilibrium state so that it can drive the vehicle to move along the beam axis with full contact. To remain the test vehicle running over the beam at constant speed, this study proposed a set of cantilever spiral spring devices to adjust the frequency by regulating the arch length of the spiral springs. From the present experimental results, the indirect bridge inspection method is applicable to frequency monitoring of a bridge. Moreover, the harder stiffness adjusted by the spiral spring device can give a more accurate prediction for measuring bridge frequencies than the softer one.