Bridge damping identification by vehicle scanning method

Abstract

A simple, theoretical framework is presented for identifying the damping ratios of simply supported beams using a two-axle moving test vehicle, equipped with uniformly spaced accelerometers and laser sensors. The latter are used to measure the relative displacements of the facing (moving) contact points on the beam, referred to as the scanning points. By adopting proper assumptions, closed-form solutions are derived for the responses of the beam and scanning points. In parallel, the scanning-point response is also given in discrete form for field applications. The road roughness effect is alleviated by using the residual response obtained as the difference of the responses of two consecutive scanning points. By utilizing the attenuation nature in the responses between two separate scanning points due to time lag, the damping ratio of the beam is derived in closed form using the Hilbert transformation. The framework proposed is verified by a finite element analysis with basically no assumptions. Its robustness is also tested for different ranges of parameters, including vehicle speed, vehicle damping, road roughness and environment noise.