Mass-normalized mode shape identification method for bridge structures using parking vehicle-induced frequency change

Mode shape identification is a crucial task in the field of bridge health monitoring. This paper proposes a mass-normalized mode shape identification method for bridge structures on the basis of its essential property of bearing vehicle load. First, the relationship between the bridge frequencies changes due to a parking vehicle, and the amplitudes of the mass-normalized mode shapes at the parking point is established through theoretical derivation. Subsequently, the algorithm and procedures to extract the mode shapes by using the frequencies measured on a two-axle vehicle that parks at different locations of the bridge progressively are proposed. Then the determination of the two-axle parking vehicle parameters and the distinctive features of the proposed method are discussed. Numerical and experimental examples of different bridge types are conducted to investigate the feasibility and effectiveness of the proposed identification method. The results indicate that the proposed method can obtain high spatial resolution mass-normalized mode shapes accurately with only one sensor on the parking vehicle.