Change Localization of a Steel-Stringer Bridge through Long-Gauge Strain Measurements

Abstract

Development of the long-gauge fiber-optic sensor provides an excellent opportunity for structural-change localization, because it measures averaged strains over a long gauge length. A practical structural-change localization, procedure using long-gauge dynamic strains in the modal space is proposed to process the ambient vibration data of a steel-stringer bridge. The proposed procedure is easy to execute by general bridge engineers; meanwhile, it has a solid theoretical basis, thus guaranteeing its effectiveness. By theoretically deriving the magnitude ratios between the analytical strain frequency response functions (FRFs) and the estimated strain FRFs from ambient vibration data, it is proved that the proposed procedure is the same as using long-gauge strain mode shapes for change location; therefore, it is effective and much simpler for general bridge engineers to use. An ambient vibration test of a steel-stringer bridge using long-gauge fiber-optic sensors has been performed. The results of applying the proposed method to the measured and simulated data of the bridge have successfully verified its effectiveness for structural-change localization.