PREDICTION OF HIGHWAY BRIDGE’S STATIC DEFLECTION BASED ON OPERATIONAL MODAL PARAMETERS

The static and dynamic properties of real highway bridges are usually separately obtained by field static and dynamic tests. The operational modal parameters that represent the structural dynamic characteristics can be easily and quickly identified by field ambient vibration measurements of highway bridges under operational conditions without the need of excitation equipment loading and interrupting the normal bridge service. This paper aims to predict the static deflection of the bridge by using the operational modal parameters to avoid the field static vehicle load testing, in which the traffic has to be closed. The modal superposition solution of the beam is derived under the action of harmonic exciting load, and then the analytical relationship between the beam’s static deflection and modal parameters is derived by setting the frequency of the harmonic exciting load to be zero. The parked vehicle method is proposed to obtain the mass-normalized operational mode shapes by using the modal frequency change due to parking the vehicle on different locations of the bridge. The static deflection prediction of highway bridges based on the operational modal parameters is realized by introducing such mass- normalized mode shapes into the derived analytical relationship between the beam’s static deflection and the modal parameters. A numerical simulation of a three-span continuous beam and a simply supported beam experiment are used to verify the feasibility and effectiveness of the method. It is demonstrated that the static deflection of highway bridges can be effectively predicted by operational modal parameters, and higher accuracy can be acquired with using more order of modes.