Fatigue Crack Identification and Lifetime Prediction for Steel Bridge Deck Structures

Abstract

Fatigue, as the governing degradation mechanism in steel bridge decks, can lead to non-inspectable cracks under the welded intersections of stiffeners to the deck plate. As a result, estimation of the remaining service life and optimization of the maintenance program of steel bridge decks become a great challenge. A comprehensive structural health monitoring (SHM) system comprising acoustic emission (AE), guided waves (GW), and strain measurements has been developed and implemented on a test bridge deck subject to fatigue loading in the laboratory environment. These measurement systems provided the necessary information to a crack growth model, e.g. crack location by AE, crack size using GW, and stress distribution from the strain measurements. It has been demonstrated that the prognosis accuracy can substantially be improved when proper crack diagnosis is performed. The estimated crack growth showed good correlation with the reference time-of-flight diffraction (ToFD) measurements: less than 20% error in length and depth estimation over 8,000,000 cycles was shown to be feasible.