Estimation of transitory changes in bending stiffness using the Hilbert-Huang transform

: A finite element model of a bridge can be calibrated based on field measurements, and then updated periodically using a structural health monitoring system. The value of a structural parameter such as bending stiffness can be adjusted to measurements using well-known modal updating techniques and monitored in conjunction with external effects such as temperature to assess the condition of the structure. A value of the parameter that is predominant during the period under investigation will be captured, however, in the case of bending stiffness, brief and transitory values could take place as a result of a section exceeding the yield point due to a moving traffic load. Given that the latter is probably the prelude of more severe damage, this paper proposes a novel two-stage method based on the Hilbert-Huang transform combined with a statistical optimization approach to characterize the stiffness changes associated with a non-linear response.