HHT‐Based Probabilistic Model of Prestressed Bridges Inferred From Traffic Loads

Prestressed bridges’ performance is strongly dependent on the health state of their prestressing cables, but unfortunately, thesestructural components are hidden and cannot be assessed through visual inspections. Moreover, conventional low-energymethods, like operational modal analysis, are inadequate due to their inability to detect the nonlinear efects of the prestressingforce on the response under heavy travelling loads. In this paper, a methodology exploiting the Hilbert–Huang transform (HHT)is investigated in which the bridge’s nonlinear constitutive force–displacement relationship can be reconstructed by analysing thetrafc-induced dynamic response, which has the features of a short-time nonstationary and potentially nonlinear signal. HHT,thanks to its adaptability to complex behaviours, is suitable for treating such type of signals and makes it possible to trace theresponse properties at each time instance, thus allowing to correlate instantaneous values of deformation with the simultaneousinstantaneous (tangent) stifness in a one-to-one relationship. Starting from a previous introductory study, and with the aim ofmaking the proposed approach suitable for real structural health monitoring applications, a comprehensive investigation isperformed considering a bridge with dynamical properties in the range of interest and realistic trafc scenarios adequatelydescribing the time series of travelling loads and relevant internal actions. In particular, three main issues are considered: (i)development of a refned probabilistic response model (to be inferred from data collected under service loads) capable toovercome troubles induced by the nonhomogeneous distributions of data, generally consisting of frequent passages of lightvehicles and rare passages of heavy vehicles; (ii) convergence analysis aimed at providing a relationship between the duration ofthe training period and the accuracy expected to infer the probabilistic model; and (iii) proposal and validation of a novelprocedure to derive constitutive model of the bridge exploiting only deformation data recorded during vehicle passages andprovide a tool for relating prestressing losses to variations in the dynamic response. Te outcomes prove the potential of theproposed strategy paving the way for real-world experimental applications